Radio Boulevard
Western Historic Radio Museum

Rebuilding the ART-13 Transmitters

General Information about the ART-13

Selecting an ART-13 Candidate for Restoration

Deciding How to Power the ART-13
(Dynamotor Operation or "Homebrew" AC Power Supply,
Dynamotor Servicing, AC Pwr Supply Schematics)

Restoration Hints and Suggestions

"Basket Case" Restoration Project & Two Other Restoration Projects

Building a Suitable AC Power Supply (includes Three Schematics)

How to Setup and Operate the ART-13 Today

Operating the ART-13 on LF 630M (472kc)

by: Henry Rogers WA7YBS/WHRM

photo: Radioman's position on a Douglas DC-4 using an ART-13 and two BC-348 receivers - Radio News Jan 1950 

When it comes to vintage WWII military radio transmitters, it's pretty hard to beat the ART-13. It's a potent 100+ watt transmitter that doesn't "weigh a ton" and has the potential to provide first-class audio in the AM mode. On top of that, parts needed for a restoration are usually easy to find and most of the circuitry is not too difficult to work on. Also, I've included construction data, including schematics, on three different ART-13 AC power supplies that I've built. Certainly every restorer/operator has their own techniques and the prospective ART-13 owner should read everything available on the Internet about these popular military transmitters to help them decide on a project that best suits their abilities and their goals.   H. Rogers - May 10, 2011

General Information about the ART-13

The Collins T-47/ART-13 is a 100 watt carrier output, AM-CW-MCW transmitter that was generally used in USN and USAAF/USAF aircraft but could also be found onboard USN ships as the TCZ installation. There were even some vehicular uses for the T-47/ART-13. The T-47/ART-13 was developed from the earlier Collins ATC Aircraft Transmitter that appeared around 1940. In 1940, the Collins ATC was tested in competition with the Bendix ATD and possibly the RCA ATB. The Collins ATC won easily as the competition lacked many of the ATC's modern features. By 1942, Collins had updated the ATC  and designated it as the T-47/ART-13. The USAAF also wanted to use the T-47/ART-13 and a very slightly different transmitter was produced for their use, designated as the T-47A/ART-13 (later designation was AN/ART-13A.) Probably the first USAAF use of the T-47A/ART-13 was in the B-29 bombers where they were paired with the BC-348 receiver and designated ARC-8. The USN had many installations in Grumman torpedo bombers and the Curtis Helldiver dive bomber along with shipboard uses. There was also a T-412/ART-13B that added a 20 channel HF and 4 channel LF oscillator by retrofitting earlier versions of the ART-13. At the end of WWII, the transmitters were designated as AN/ART-13, AN/ART-13A and AN/ART-13B. There are many other different designations assigned to ART-13 transmitters that are essentially identical to the three basic ART-13 variations. Various end users account for most designation variations found.

Basic Transmitter Circuit - The ART-13 uses a permeability tuned oscillator designated as a VFO (although later these types of VFOs were referred to as a PTO - permeability tuned oscillator - by Collins.) The VFO-PTO operates from 1000kc to 1510kc that is tuned using two ranges that are switched alternately as control A is changed. The first range is from 1000kc to 1200kc and the second range is from 1200kc up to 1510kc. The VFO tube is a 837. The VFO-PTO output is routed to the first Multiplier that increases the frequency for the various tuning ranges of the transmitter. Below 6.0mc only the first Multiplier is used as either a doubler, tripler or quadrupler depending on the frequency desired. Above 6.0mc the second Mulitplier is also used (only as a tripler) to achieve these higher frequencies. Two 1625 tubes are used as the Multipliers. The Multiplier(s) feed the 813 PA and its output is matched to the antenna using a tuner that can select either an L or a Pi network depending on the frequency and load matching necessary. Controls C, D and E tune the antenna matching network. AM is achieved using a 12SJ7 speech amp and a 6V6 amplifier that drive the pair of 811 modulator tubes. CW is via a keying relay operating the PTT line. The transmitter can be tuned from 2.0mc up to 18mc.

Power Requirements and Accessories - The T-47/ART-13 power requirements were supplied by a dynamotor that ran on the aircraft +28vdc battery/charger system. The aircraft battery buss supplied the +28vdc@10Amps necessary for the transmitter's tube filaments and relay operation while the dynamotor provided a dual output of  +400vdc and +750vdc. The dynamotor would have the two B+ levels connected in series for the HV Plate ( +1150vdc) below 20,000 to 25,000 feet altitude but a barometric pressure switch (located inside the dynamotor housing) would separate the outputs at higher altitudes and only allow +750vdc maximum to prevent arc-over. There were four types of dynamotors used. The earliest was the DY-11 that was used with the ATC. The DY-12 was used with the ART-13. The DY-17 was used with the ART-13A and WWII versions of the ART-13B. Post-WWII, there was a DY-17A produced. All four dynamotors are interchangeable to power any ART-13. The shipboard TCZ featured two types of power supplies, a 115vac operated, floor-mounted pedestal-type power supply that provided the required +28vdc, +400vdc and +1150vdc directly to the transmitter. The 115vac unit utilized a motor-generator that provided +14vdc and +28vdc @10A (the +14vdc was required for relay operation inside the AC or DC operated TCZ power supply and the +28vdc operated the tube filaments and relays in the transmitter.) The +400vdc and +1150vdc were provided by standard AC transformer power supplies. The115vdc operated TCZ power supply used two dynamotors that ran on 115vdc input and provided +14vdc and  +28vdc output on one dynamotor and +400vdc and +1150vdc on the second dynamotor. The USMC had a vehicular set-up that installed an ART-13 transmitter with a BC-348 receiver that operated from the back of a Jeep and ran on the +28vdc battery system with HV provided by a DY-12 dynamotor. The antenna was a whip.

photo above: US Navy T-47/ART-13 built by Collins Radio Co. ca. 1942

Power and Remote Receptacles
- There are three large multi-pin connectors on the left side of the cabinet for applying voltage input, remote control operation and LF control line. The connectors are marked as follows (from front to rear:)

PLUG U-8/U - Remote channel select, standby, audio, PTT line (T-R)
PLUG U-7/U - Voltage inputs from dynamotor, PTT line (T-R)
PLUG U-11/U - Low Frequency Loading Coil (Tuner) PTT line (T-R)

The U-11-U connector is only used with the CU-32 Antenna Loading Coil (LF Tuner.) The U-8/U connector is used with the pilot's remote that allowed remote control of the ART-13 from the pilot's seat. Also, receiver remote standby is accessed from the U-8/U connector. U-7/U is the connector for applying all voltages to the transmitter and providing the ability to turn the ART-13 "on or off."

Autotune and Vacuum Tube Information - The T-47/ART-13 featured an advanced Autotune system that would automatically "tune" up to 11 preset channels (10 channels plus one LF channel) selectable by a front panel switch. The Autotune system would mechanically set the transmitter frequency and output network components to presets that then would result in the transmitter matching a properly selected antenna. The ART-13 didn't automatically load and tune itself to the antenna load as more modern Collins' transmitters would (e.g., the T-195) but assumed the operator would connect the proper type of antenna for the channel selected on the ART-13. The Autotune cycle took about 25 seconds to complete. Switch position MANUAL would allow manual adjustment of the tuning  without disturbing the Autotune presets. MANUAL had to be selected with the transmitter powered up so the Autotune would properly "mechanically" select the MANUAL position (in other words, with power off you couldn't just place the switch in MANUAL and be in MANUAL.) The T-47/ART-13 uses an 837 as the variable frequency oscillator, two 1625 tubes are used as multipliers, an 813 as the power amplifier and two 811 tubes as the P-P modulators. There are also two small modules. One provides the audio amplifier and sidetone amplifier using two 6V6 tubes and a 12SJ7 tube and the other module, the MCW/Frequency Calibration Indicator, uses two 12SL7 tubes and a 12SA7 tube. FCI allows the operator to calibrate the frequency of the transmitter by providing a 50kc calibration signal derived from a 200kc crystal oscillator. The earlier ATC transmitter used a slightly different FCI module that used two tubes and had a rather large plug-in crystal (see interior photo of ATC below.)

Low Frequency Coverage and More Accessories - The standard ART-13 transmitter frequency range is from 2.0mc to 18.0mc, however many Navy ATC and T-47/ART-13 transmitters and later USAAF T-47A/ART-13A transmitters were equipped with a plug-in Low Frequency Oscillator (LFO) module that allowed the transmitter to operate from 200kc to 600kc or 200kc to 1500kc (at somewhat reduced power, CW only for electrically short antennae.) Early LFOs had a frequency range of 200kc to 1500kc in six ranges designated as O-16/ART-13, while the later LFOs cover 200kc to 600kc in three ranges and is designated as O-17/ART-13A. The LFO modules used a single 1625 tube. When the LFO is in operation the ART-13 Multiplier section is bypassed and the LFO output directly drives the PA.

There are some indications that the Navy set-ups used the 200kc to 1500kc LFO while the USAAF used the 200kc to 600kc LFO. Many versions of the T-47/ART-13 will have a blank plate installed where the LFO module was installed designated as NX-128/ART-13. These LFO "dummy panels" had a resistive load included that substituted for the LFO's 1625 filament load. It's possible the most of the LFOs were removed later in the ART-13's life as the transmitters were usually on HF after WWII. According to the USAF Extension Course 3012 book on "Radio Mechanics from 1950," the Navy was still using LF after WWII but the USAAF wasn't.

When switched to LF, the ART-13 PA output is capacitively coupled (via the plate blocking capacitor) to "LOADING COIL" terminal J-117. Selecting the LF position also disconnects the ART-13 internal HF antenna matching network. The aircraft installations (when operating LF) would require the CU-25 or CU-32 antenna tuners (called Antenna Loading Coils.) These units provided the antenna matching networks for low frequency operation of 200kc up to 600kc. There was also the CU-26 that provided antenna matching for 500kc up to 1500kc. The CU-32 allows the use of either trailing wire or fixed antennae while the CU-25 and CU-26 are for trailing wire only. Generally, the Navy used the CU-25 and CU-26 while the USAAF used the CU-32.

Also most installations on aircraft included a small Remote Control Panel designated as C-87/ART-13 or a smaller remote designated as C-470/ART-13. The remotes allowed the pilot to operate the transmitter from the cockpit. The larger C-87/ART-13 has a hand button for keying the ART-13 and allows a microphone connection at the remote. A typical aircraft ART-13 installation could select from a couple of different remotes, three different types of LF antenna tuners, a triple fixed capacitor (auxiliary capacitor for antenna loading below 7mc) and various knife switches. There were at least a couple of different shock mounts that were available depending on the version of ART-13 and where it was located. Shock mounts provided vibration isolation and elevated the transmitter to allow convection cooling. Most installations seen in vintage photographs usually have two BC-348 receivers.

photo left: Inside a Collins' version USN T-47/ART-13 showing the LFO module installation. Also, the later three-tube version of the MCW/FCI module is installed. Note that the chassis is painted gray on Collins' version

The Chassis Layout - To the left is a photo showing the chassis of a Collins-built T-47/ART-13. This transmitter has the Navy version LFO installed. Also, this is a fairly early version of the transmitter so there are some differences when compared to the T-47A/ART-13 versions. Of note is the lack of an interlock switch which on the early versions allows you to easily operate the transmitter with the lid off. The module to the lower right is the Audio Amplifier unit and directly behind it is the 837 VFO tube. Behind the VFO tube is the FCI/MCW module and to the left of it are the two 1625 multiplier tubes. The module in the center of the transmitter is the LFO. In the section at the rear of the transmitter, to the left side is the modulation transformer from which its plate leads connect to the two 811 modulator tubes. To the right of the 811s is the 813 PA tube. The left-center section of the transmitter contains the matching network and the LF relay (next to the LFO module.) On the far left is the vacuum TR switch and behind it is the keying relay. The round ceramic unit in front of the vacuum TR switch is the inductive pickup for the Antenna Current meter.

T-47A/ART-13 or AN/ART-13A - The somewhat later USAAF T-47A/ART-13 aka: AN/ART-13A version added some minor improvements to the transmitter with a vernier scale on the VFO Fine Tuning, a top lid interlock switch, a different bottom plate with built-in guides for the shock mount and a white ceramic insulator bell on the antenna connection being among the most apparent changes. This model of the transmitter is often found built by various contractors with Stewart-Warner being one of the most often encountered. The contractor identification is most often found on the metal tag mounted on the right side of the transmitter as initials incorporated into the contract number.

T-412/ART-13B or AN/ART-13B - There was also a T-412/ART-13B that added a 4 channel LF/MF and 20 channel HF crystal oscillator module, the CDA-T in place of the LFO module. The CDA-T was built by Communications Company, Inc.(aka COMCO,) who generally supplied the module with a full installation kit that included extensive instructions and directions for the conversion of either the ATC, the T-47/ART-13 or the ART-13A. When the CDA-T was installed and the transmitter fully converted to the "B" version then, with the selection of each of the transmitter channels 1 to 10, two different crystals could be selected giving the user two frequencies per channel or a total of 20 HF channels in all. Also with the CDA-T installation a "frequency extension" modification was added that changed the lower end of the frequency coverage down to 1670kc. The LF position allowed the selection of four crystal controlled frequencies on the CDA-T module. The remote used with the "B" version will have a toggle switch to allow selecting either crystal frequency per channel selected.

All "B" versions of the ART-13 are conversions of earlier ART-13 or ATC transmitters. Be aware that you can't just install the COMCO module and have your ART-13 become a "B version. In fact, the CDA-T can't even plug-in to an unmodified ART-13. The installation of the "B" version CDA-T module required extensive modification of the transmitter circuitry along with the addition of a second Jones Plug for the module and an additional wafer for the REMOTE-LOCAL switch along with several additional components (supplied in the kit with the module.) Most ART-13B conversions that were performed by the military during WWII will have riveted tags installed to identify the frequency extension toggle switch and another tag riveted above the original transmitter data plate that identifies the conversion to T-412/ART-13B. Post-WWII conversions generally don't have these riveted tags installed. Since there was no modification to the Autotune of the ART-13 transmitter, each of the A/B crystal channels had to be set very close in frequency to each other, otherwise the transmitter wouldn't be tuned for one or the other of the lettered crystal channels.

photo left: The Crystal Oscillator Unit for the ART-13B. Built by Communications Company, Inc. (COMCO.)

Post-WWII Use - The T-47/ART-13 had a very long life. Introduced around 1942, actively used during and after WWII and well into the sixties. The Grumman HU-16 air-sea rescue amphibians were equipped with ART-13/BC-348s until the late 1960s. The USSR also produced a copy of the ART-13 that they used up to the late 1980s (the R-807.)Surprisingly, the ART-13 was available on the surplus market quickly after WWII ended. By 1946, one could purchase an ART-13 with all of the accessories for between $75 and $125. Most were fully checked out and guaranteed to work. Many hams bought the ART-13 as a station transmitter, some operating the transmitter on its dynamotor while most built AC power supplies instead. The availability changed fairly quickly and by 1950 only a few surplus dealers offered the ART-13. Civilian airline companies also began using the ART-13 in various commercial airliners. Many were converted to the B version for multiple crystal-control channels (there was also a C version which was similar in function.) Some ART-13s were supplied to civilian aircraft in new condition with priority sales which probably accounted for the shortage in the surplus market after 1950.

Because of its long useful life, most T-47/ART-13 transmitters found today will have many scratches and a few dents and paint scrapes. Sometimes non-matching modules will be encountered with some parts having MFP applied and others that are bare. A book containing brief instructions and the calibration settings for specific frequencies is usually stored in the metal pocket underneath the transmitter.  Earlier versions of the transmitter will have a somewhat thinner (and always missing) book not "chained" to the pocket. This earlier book is specifically for the two tube version of the MCW/FCI module used in the ATC and early T-47 transmitters. Later versions have a thicker book that is specific for the three tube version of the MCW/FCI module used in late T-47 and all ART-13A versions. The later book has a plastic tubing covered chain that was supposed to keep the book "tied" to the transmitter. This later book is also usually missing on most transmitters (although the same information is in the standard manuals.)  >>>

photo right: The Collins ATC chassis showing some of the differences between this very early version and the later ART-13. Notice the earlier, two tube version of the MCW/FCI module (the large cylinder upper right is the crystal) and the absence of the large LF relay K-105 (smaller version is in ATC.) Also note the Collins tag on the modulation transformer.

>>>  Luckily, thousands and thousands of T-47/ART-13 were built and spare parts are very easy to find which allows for the fairly easy restoration and maintenance of these durable and potent transmitters.

Selecting an ART-13 Candidate for Restoration


Preliminary Considerations

Assessing your potential restoration candidate prior to purchase is important for a successful completion of the project. Choosing the right ART-13 is certainly going to determine how long it takes you to complete the project and get it "on the air." There are a couple of tests that should be made if you have access to the transmitter before purchasing. Also, some things to look for when buying on line.

Technical Difficulty of Restoring an ART-13 - The ART-13 is a robustly-built but light-weight, compact transmitter. Since it is fairly small most of the components are installed into tight quarters and accessing most of the transmitter circuitry will require some disassembly. Fortunately, most of the transmitter design and construction allows easy disassembly to access and work on various parts of the circuitry. If you have serious problems in the Autotune section, this is difficult to disassemble and some of the parts are somewhat delicate. Same goes for the VFO-Multiplier sections which are difficult to access and the Multiplier uses very delicate stacked trimmer capacitors. Though the Audio and MCW/FCI modules are easy to remove, the components are densely mounted under the chassis. Most ART-13s will have MFP applied and this will compound the difficulty of any soldering work that might be required. Certainly an AC power supply (if opt'd for) will be the most time consuming to design and build. >>> >>>  You should have the following skills when taking on an ART-13 project. You should have some experience working on tube-type transmitters and working around high voltages. You should be experienced in full disassembly and reassembly of electronic equipment. If you decide on an AC power supply, you should possess "homebrewing" skills, that is, sheet metal working, component layout, proper wiring dress, etc. You should have good technician skills, possess a good soldering technique and use real SnPb solder with first class soldering equipment. You will need good quality test equipment. You will need a set of spline wrenches (also called Bristol wrenches) for all set screw applications. An oscilloscope is essential during testing and set up of the transmitter. You should possess good troubleshooting skills. Most hams that have worked on several tube-type transmitters and have built some radio equipment will have the necessary skills to complete the restoration of an ART-13.
Selecting a Candidate for Restoration - There are a lot of ART-13 transmitters for sale at swap meets, on eBay, from Fair Radio Sales or from various online sources. ART-13s are not hard to find. But, what is hard to find is a good condition, all original and complete ART-13. Most of the transmitters that are for sale look like the one in the photo to the right. Not a good candidate unless you are experienced and looking for a real challenge*. This candidate's condition is obvious but many times the ART-13 you are looking at can have serious problems that aren't obvious at all. A thorough inspection followed by actually testing a couple of the components can help "weed out" a transmitter that is going to need a lot of repair and restoration work.

A good candidate should be fully assembled and have all of its modules installed. A few missing tubes are okay since they are easy to find and not terribly expensive. Be aware though, missing tubes should be taken as an indicator that the transmitter was considered a "parts source" at one time and may actually have some operational problems - not always - but definitely investigate further if all of the tubes are missing. Meters should be in good condition and they are easy to test while in the transmitter. The meters are not difficult to locate but the same caveat as with missing tubes should be considered. Generally, a complete and good condition transmitter means it has always been stored correctly, has not been abused and probably has a pretty good chance that nothing serious will be found wrong in the circuit or with the components. Be skeptical though! Even though the transmitter might look great, it could have a serious, difficult to solve problem that kept the transmitter from ever being used, thus it's excellent appearance. Definitely, any transmitter that is missing parts should be considered  a "restoration project" that is going to require time searching for parts and will need more time to get the fully operational.

*See section below "T-47A/ART-13 'Basket Case' Restoration" to see how this transmitter turned out.

photo right: T-47A/ART-13 "parts set." Note, even the multimeter glass is broken. Although restorable, this one would be a definite challenge.

Inspecting the ART-13 Before Purchase

Thorough Inspection of the Transmitter - If you have access to the transmitter prior to purchase you can look it over in detail. The two "easy to remove" modules should be present. The three-tube MCW/FCI module is easy to find if it's missing but the Audio module is more expensive and a little more difficult to locate. Check the interlock switch on the T-47A/ART-13 versions since if the transmitter is placed upside down with the lid off (for quick and careless repair work) more than likely the switch will be broken. Check the wiring for anything cut or missing. >>> >>>  Check for broken parts. The Antenna vacuum switch is sometimes broken since it is a glass unit. Undo the locking bars and see if the controls rotate easily. Don't "force" any controls that seem stuck - you'll only break something. The controls should freely rotate. Check the condition of the push connectors on the left side of the transmitter and make sure they aren't corroded and stuck. Also, check the condition of the U/7 connector and make sure the pins aren't bent or corroded. That's about all you can check visually. If the seller is agreeable, check the Modulation Transformer and the Meters as described in the following sections.
Testing the Modulation Transformer - This is probably the most important part of the transmitter that is sometimes missing and other times non-functional. Finding a good condition replacement (if you need one) is difficult and somewhat expensive. You will want to know "up front" if the ART-13 you're contemplating buying has a non-operational modulation transformer as this will seriously affect its selling price. You'll need to have a DMM (Digital Multimeter) to check the modulation transformer. You will be measuring the DC resistance (DCR) of the windings. This test is not a 100% indication that the modulation transformer is perfect but it's a pretty good test. Also, if the DCR of a tested winding reads open, you then know 100% for sure that the mod transformer is bad. Take care to make good contact to the terminals with your test probes, especially if the mod transformer is coated with MFP. Note that each of the seven terminals are numbered. The three terminals on the left side (assuming you're in front of the transmitter) are from left to right looking at this side 6, 7 and 2. On the right side the four terminals are left to right 1 and 3 on top and 4 and 5 on the bottom.

Be aware that the 813 screen windings have a different DC resistance on early units. The change occurred about the middle of the ART-13A contracts. It looks like the wire used for the the screen winding was increased in diameter for better durability which would then have the same turns ratio but a lower DCR. It's also possible that many of the earlier Mod transformers were noisy. My T-47/ART-13 has the earlier Mod transformer and it is very noisy when at full modulation. My AN/ART-13A sn: 417ACG however, has the later Mod transformer and it is quiet regardless of the modulation level. I have also tested ART-13A sn: 2054 that has the early style mod xmfr and have found that it also is somewhat "noisy." The implication is that the lower screen DCR (heavier gauge windings) helped to reduce the mod xmfr "talk-back."    >>>

>>> Here is the DCR between the various terminals with the Modulation Transformer installed in the transmitter (with power off, of course.)

Terminal 2 to Terminal 3 = 136 ohms DCR

Terminal 2 to Terminal 1 = 123 ohms DCR

This test measures the DCR of the P-P 811 modulator plate winding. Terminal 2 is the CT of the winding.

Terminal 7 to Terminal 6 on early mod xmfrs = 150 ohms DCR

Terminal 7 to Terminal 6 on later mod xmfrs = 38 ohms DCR

This test measures the DCR of the 813 screen winding

Terminal 4 to Terminal 5 = 112 ohms DCR

This test measures the DCR of the 813 plate winding

If the transformer measures close to these DCRs, it is likely in good condition and useable.

NOTE: If you want to check the windings to chassis for case shorts be sure to place the CAL/TUNE/OPERATE switch in OPERATE. If you have that switch in the TUNE position, you'll have a 25K short to chassis on the 813 screen windings.

Testing the Antenna Current Meter - This is an AC current meter that is driven with an adjustable core, single-turn transformer. The meter is .250mA FS and should to be checked with an AC source, such as a Function Generator. The Function Generator will have a very low output Z - probably 50 ohms. The polarity to the meter doesn't matter but you will have to disconnect it from T-102, the Antenna Current Transformer. Set the function generator frequency to anything higher than 100kc - it's not critical. It takes a pretty high level sine wave signal to move the Antenna Current meter needle but 15 volts Pk-Pk should read 2.0 Amps on a working meter. If a Function Generator is not available, a Digital Multimeter (DMM) will indicate around 3.0 ohms DCR across the terminals in both directions (due to the internal dual thermocouple) but the meter needle should not move with DC applied (from the DMM measuring DCR.) Again, you'll have to disconnect the meter for testing by either method. Generally, these meters were pretty reliable and are seldom non-functional. Testing the Multimeter - This meter is a 1mA FS DC meter. Measure the DCR across the terminals and you should read about 40 ohms DCR.  NOTE: Be sure to only use a Digital Multimeter (DMM) for this measurement. Older style VOM meters can apply enough voltage in some of the ohm scaling to do possible damage to the ART-13's multimeter.   With a DMM, you will see some deflection of the meter needle. Be sure to observe the correct polarity. You are only checking the meter's continuity with this test, not its accuracy. To check the accuracy you would need a small DC voltage source that is adjustable and a 300 to 1000 ohm load resistor. Use the DMM set on DC mA with the FS at no higher than 10mA. Use the load resistor to limit the DC voltage source and connect the meter, the load resistor and the DDM in series with the DC voltage source. Adjust the DC voltage for a FS meter reading and then look at the DDM. It will read how much current is necessary to drive the meter FS. It should be very close to 1.0mA Toilet Seat Covers - These are the protective covers that are usually on the KEY, both SIDE TONE and the MICROPHONE jacks. The T.S., or Throttle Switch (remote PTT,) jack doesn't have a protective cover. These are mentioned here because some ART-13 variations will be found without the Toilet Seats installed. This is correct for certain sub-model variations. All ATC versions don't have toilet seats. NT-52286 is another variation that did not have the protective covers and there may be others. Check the panel carefully for originality if the Toilet Seats are missing. Original installations use rivets to mount the covers so any removal operation would be obvious. 
Buying an ART-13 Online - If the only source available to you is eBay or or some of the other online venues, your inspection is going to be cursory, at best. Photos only show so much and detail is often lacking. Most of the time the seller doesn't show what is important and has several irrelevant photos. You should ask questions or ask for more photos. Generally, if the transmitter appears to be in great condition, then it probably is complete and was stored carefully. You won't know the condition of the components unless the seller has taken the time to test them and will guarantee their condition. Buying online, especially on eBay, will result in paying the highest price, plus paying for shipping (where damage may also occur.) Since you will be paying "top dollar," you should be assured that the transmitter is in good condition and will be packed carefully for shipping. Modified ART-13 Transmitters - The ART-13 was the subject of many modifications generated by the CQ magazine crowd. CQ published "The Surplus Conversion Handbook" which contains two or three articles on ART-13 "modification for ham use." Although we cringe today at such "hacking," it was commonly done in the fifties and sixties. Consequently, finding an ART-13 in modified condition is fairly common. Some of the mods were intended to increase the transmitter's frequency coverage. There were mods to extend the lower end to cover 160M, although many ART-13s will tune about 25kc into the top of the 160M band without any modification. There were other mods to extend the upper end to 10M. The 10M mod pretty much did extensive damage that is difficult to restore to original. Also it's very common to find some of the Antenna/Condenser/Loading Coil/Ground push connectors replaced with SO-239 UHF coax receptacles. Again, damage to the connector panel is usually irreparable.

Try to stay away from modified ART-13 transmitters. There are a several minor upgrades or modifications out there that have some benefit and enhance the performance but generally the ART-13 can be operated in its original configuration without any problems.

Manuals - Since so many of the manuals are available on-line, it's probably a good idea to download them and become familiar with the transmitter before you actually purchase one. That way you'll know what to look for and how to describe certain parts of the transmitter that are somewhat unique.

T.O. 12R2-ART13-2 is the Maintenance Handbook for the ART-13A and is a very good source of information. Available on BAMA (Boatanchor Manual Archive)

NAVWEPS 16-30ART13-5 is the Maintenance Handbook for the ART-13. Available on BAMA

Several other manuals were published over the years. Some are available on-line but the majority of these lesser known manuals have to be purchased from other sources.


Deciding How to Power the ART-13

By now you should be considering how you're going to power up your ART-13 when you finish the restoration. I'm not trying to talk the potential ART-13 operator out of using an original Dynamotor set-up but there are several "pit-falls" that will surface when attempting this method of operation. The initial purchase of the equipment necessary to operate the dynamotor will be fairly expensive but one should remember, once a high-current power supply is purchased, you can run almost any dynamotor set-up with it. However, due to the fact that many ART-13 owners aren't necessarily vintage military radio enthusiasts, building an AC-operated power supply is the least expensive and most common approach taken to power up an ART-13. Usually the most time consuming part of the entire ART-13 restoration project is deciding how to power the transmitter and then obtaining the necessary components to accomplish the task. The following information comparison may help you come to a decision.

Using the Original Dynamotor Set-up

Dynamotor Details - Any versions of the ART-13 transmitter can be powered by any of the four versions of dynamotor that were produced. The original ATC was supplied with the DY-11 dynamotor. The T-47/ART-13 was supplied with the DY-12. All later ART-13 transmitters used the DY-17 or DY-17A dynamotor. To power any of the dynamotors requires using a shielded cable that uses two 8 gauge wires that are connected to the dynamotor with a large two-pin Cannon plug and are then routed to the +28vdc power source. There is a small third pin for the shield in the original connector. The dynamotor generally requires about 32 amps at +28vdc at full output.

The dynamotor is connected to the ART-13 via a shielded cable that utilizes two different types of Cannon plugs. The dynamotor-side uses a 10 pin male plug and the transmitter-side uses a 10 pin female plug. All three of the original Cannon plugs are available for many sources (although they are not cheap!) Generally, the power cable has to be built. The ART-13 power cable uses two 14 gauge wires (pins 5 & 6,) five 18 gauge wires and two 16 gauge wires and a HV wire (pin 10.) I use the center conductor and insulation from a length of RG-58 coax. The cable has to be shielded. I use the braid removed from RG-8U coax. Push the coax shield together to expand its inner diameter and then sleeve it over the 10 wire cable. Once in place, pull the shield tight and wrap the entire cable with two layers of electrician's tape. Install the connectors and be sure to connect the shield using a "drain wire" to the connector shell on both ends. The ART-13 manual will have a schematic and breakdown of the the power cable. Build the +28vdc cable in the same manner. Use 8 gauge wires and connect the shield to the small pin of the connector. Be sure that the shield is connected to the negative of your high current DC power supply.

The differences in the four versions of the dynamotors are locations of the reset switches which are on top of the base on the DY-11 and DY-12. The reset switches are on the front panel of the DY-17 models. The end bells differ on all three models with the DY-11 having a circular screened vents, the DY-12 has six spokes in its screened vents and the DY-17 has three spokes in its screened vents. Although there are some minor circuit changes between the models these changes don't affect how the dynamotors power any of the ART-13 transmitters.  >>>

>>>  The photo above shows a DY-12 dynamotor which was originally supplied with the T-47/ART-13 version of the transmitter. This particular dynamotor was built by Wincharger Corp. (aka Winco) and, although in kind of "rough" condition, it does function correctly. The input and output box connectors are identical for all versions of the ART-13 dynamotors. The photo right shows the DY-12 in service. This shows how the dynamotor connectors look.

The DY-11 and DY-12 are difficult to find and usually are in original condition which means they may require some rebuilding to function well. The DY-17 is the more common version but it's still difficult to locate. Since most casual ART-13 "parts collector-dealers" think the DY-17 is the only proper dynamotor, it is usually the most expensive one to purchase, if it can be found. Same holds true for the later DY-17A.

Another word of caution on dynamotors in general,...dynamotors may be found that have problems that can't easily be repaired. A shorted armature might require rewinding and, if you can find anyone to do it, the costs will be staggering. A recent quote to rewind a DY-17A armature was $3300 from a rebuilder in Los Angeles! If you want to go the dynamotor route, try to arrange a test of the unit prior to purchase to see if it will operate correctly when powering an ART-13. Even with a shorted output-side armature, the dynamotor will rotate since the motor-side winding is okay making the tester think the dynamotor works. However, under load (trying to operate an ART-13) the defective dynamotor will "bog down" and not rotate at speed due to the excessive load of the shorted armature and the ART-13. You must test the dynamotor actually powering up an ART-13 before you know it's usable.

The specifications for the input and outputs are as follows:

Input:   +27vdc at 32amps - with the aircraft aloft, the charging buss was nominally running at +28vdc (sometimes slightly higher) and this is where the dynamotors work best. The +27vdc spec allowed for some voltage drop in the power cable from the dynamotor to the buss.  

Outputs:   +400vdc at .750amps   and   +750vdc at .350amps

Dynamotor Operation - If you decide to go original and use one of the dynamotor-battery combinations, here's some other things to think about.

Running the Dynamotor only on Batteries (not recommended) -  Using two 12vdc deep-cycle marine batteries connected in series to provide +24vdc for dynamotor/xmtr power is not recommended. The batteries will have to be kept charged in some manner. Charging lead-acid batteries in the house or ham shack can be dangerous and certainly is smelly. Additionally, the batteries alone will only provide about +26vdc after charging and the voltage will drop rapidly as the transmitter/dynamotor is in operation. In the airplane, the transmitter/dynamotor ran on a battery-charger system that provided an almost constant +28vdc while the airplane was aloft. This is where the ART-13 runs best. Typical power output using the dynamotor on just batteries will be around 60W to 70W. With a charging system (+28vdc) power output will be around 100W. This is due to the speed that the dynamotor turns. The +28vdc turns the dynamotor at its rated RPM where it delivers the rated voltages. At lower battery voltages, the dynamotor speed drops and so does the voltage along with the transmitter power output.

Running the Dynamotor with a High Current AC PS (best solution) -  To eliminate the batteries and run the dynamotor on a high-current +28vdc power supply is problematic due to the horrendous starting current required to operate the dynamotor. Although when turning at full speed (and powering the transmitter) the dynamotor load and the transmitter load requires around 35 amps, the initial starting current required by the motor section of the dynamotor is close to 100 amps. Although this starting current is very high it only lasts for a few milliseconds, that is, until the armature begins to move at which time the current demand drops rapidly as the motor armature comes up to speed. Even though the high current demand is for a very short duration, many modern, high current DC power supplies with current fold-back circuitry or other types of protection circuits will "see" the dynamotor as a "short circuit" and prevent the power supply from operating. The exceptions are some of the earlier military heavy-duty AC power supplies. These are early style "linear" supplies that can handle the surge current demand since it only lasts for a few milliseconds. The GRC-106 power supply is rated at +28vdc at 50Amps and, if one can be located separated from the transceiver, it will operate the DY-17 (et al) dynamotors. Also, the heavy-duty "battery charger" unit, the PP-1104, can be used to supply +28vdc at well over 50A. These types of heavy-duty power supplies can provide enough current to start the ART-13 dynamotors. Also, there are portable airport-type power supplies used for starting airplane engines. These are available up to 200 amps at +28vdc. However, "expensive" is an understatement. More details on the PP-1104 below.

Running with a Combination of Batteries and Hi-I AC PS (not necessary)Another solution is to run the lead-acid batteries with an adjustable 0 to +50vdc power supply capable of providing at least 40 amps. That way, you can adjust the power supply to have the battery system at +28vdc and simulate a charging system. The batteries will provide the 90 to 100 amps necessary for the initial starting current of the dynamotor. In essence, this combination simulates how the ART-13 operated while on the aircraft aloft. This system may work with high current linear power supplies that have current fold-back circuits, such as Astrons. Experimentation would be necessary since I've never tried it, but I've heard of it working with the 35A or 40A Astrons. However, the hassle of running both batteries and a high current power supply seems to complicate a problem that can be easily solved by using either the PP-1104 or GRC-106 PS.

Using the PP-1104 to power the ART-13 with a Dynamotor - Details - The PP-1104 was originally supplied to the military as part of a battery charging system. To say that the power supply is robust is an understatement. It is capable of supplying well over 50 Amps at 28vdc and has the ability to adjust the output voltage to compensate for the load. There are two versions of the PP-1104, the early version that uses a large selenium rectifier and the later version that uses silicon diodes. Both have similar performance specifications. Early versions are designated as PP-1104-A/B and later versions are designated as PP-1104-C. Many different contractors have built these power supplies over many years so there are variations galore as to minor construction details and paint colors, etc., but the specifications and performance are all the same. The physical size of the PP-1104 is about 24" tall by about 20" wide by about 12" deep. The weight is over 100 lbs for the early versions and just at 100 lbs for the later versions. The power requirements are either 115vac or 230vac with the current draw at between 10 amps to 24 amps depending on the ac voltage used and the load. The power supply can also be set up for 12vdc at over 100amps capability. The circuit uses two 12vdc solid-state linear power supplies that can be connected in parallel or in series via front panel links. Meters provide constant monitoring of output voltage and current. A front panel switch allows for setting the output voltage in roughly 10 steps. Output voltage should not be adjusted with the unit turned on however. Set with power off and then check with power on. The circuit on the later PP-1104 supplies uses a magnetic amplifier to increase the current capabilities. Also, a very small internal power supply feeds into the main supply to provide voltage regulation.

The PP-1104 was built for years by many different contractors. The Gladding-Keystone version I have is from 1967. The latest contract version I've seen was from 1989. With a little searching, a PP-1104 should be pretty easy to find. The selling prices vary but expect to pay around $200 to $300 for a decent one.

Curing RFI in the PP-1104 - Some PP-1104-C versions are rather noisy in the RF spectrum and the magnetic amplifier will produce some RFI. These units can be set-up with shielded AC lines coming in and shielded cables for the output. Be sure that the case of the power supply is also connected directly to the station ground system with a 10 ga. ground wire. Additionally, it's a good idea to bypass the AC line in with .01uf capacitors to chassis and to also bypass both the positive and negative output terminals with a .22uf tubular and a .01uf ceramic disk capacitors connected to chassis. Be sure to check the 10-32 screws that mount the top cover, the bottom and the back cover to see if good grounding contact is being achieved. Usually the paint is very heavily applied and quite hard which insulates the covers from making good contact to the main frame. It's usually necessary to use a small sanding disk to remove the paint where each screw head makes contact and remount the screws using toothed lock washers. This will provide an "RF tight" enclosure which helps considerably in reducing RF noise. Thanks to Jerry W6JRY for the PP-1104 RFI suggestions.

Operation - Using the PP-1104 to operate dynamotors eliminates most of the headaches since the power supply is capable of providing the starting current without hesitation. Also, since the PP-1104-C can be adjusted to over 40vdc output voltage, adjusting to 28vdc under load is easy and allows the ART-13-dynamotor combo to run efficiently and with maximum RF output power (100 to 110 watts typically.) You might find that the unloaded voltage (when you're not transmitting) might be a little high running up to maybe 30vdc but it is possible to adjust the PP-1104 to find the best compromise of loaded versus unloaded conditions. You shouldn't adjust the PP-1104 when it is operating, so some experimenting will be required. Also, if you use the largest gauge wire that will fit in the connector sockets in your ART-13 to Dynamotor cable and the PP-1104 to dynamotor cable, the less voltage drop you'll experience and thus the less voltage change between load and no load conditions. Typical excursions with large gauge wires in your cables is between 1vdc and 2vdc maximum.Usually, you can set the PP-1104 for +28.5vdc no load and under load the voltage will be +27.5vdc, which is ideal. Remember that the ART-13 tube filaments are running on the PP-1104 in both transmit and receive, so try to keep the supply voltage as close to +28vdc nominal as possible.

photo right
: A 1967 PP-1104-C built by Gladding-Keystone Corp. A little bit scratched up but still working fine. Note that the voltage meter (left) is a replacement meter. Also, note the small moving dolly used for easy relocation of this heavy power supply

Servicing the ART-13 Dynamotors

This write-up relates the servicing procedure (with photos) of the DY-12 version of the ART-13 dynamotor. The servicing procedure is the same for each of the ART-13 dynamotor versions. There will be slight differences in end bells and the base but, internally, the DY-11, DY-12, DY-17 and DY-17A, are the same.

Most of the dynamotors we encounter haven't been serviced in a very long time. Maybe the original grease is still in the bearings. You never know until you take the dynamotor apart and check. Generally, if you remove the end bells you can access most of the areas of interest. You'll want to check the following:

1. Condition of the brushes

2. Condition of the commutator segments

3. Type and amount of grease in the bearings

Remove the brushes to check length and the surface that contacts the commutator. You will have to remove all of the brushes even if the brushes are in good condition because of the cleaning solvents used to remove the old bearing grease could contaminate the brush surface. Keep the brushes clean by removing them before the cleaning process. Mark each of the brushes with a small dot(s) of paint for proper orientation and correct location. One dot, two dots, three dots, etc. It will aid in correct reassembly. If  you have several colors of paint, then only one dot is required per location and orientation.

The brushes should fit the contour of the commutator. The brushes should also be long enough to not run hot. Usually about 1/4" minimum above the bottom edge of the housing is okay. If the brushes are too short then they should be replaced with new brushes. If the brushes need replacing then you'll probably have to go to a motor rebuilding shop or other source of brushes to find a set that are the correct dimensions. Normally, the original brushes are okay because the military serviced the dynamotors when they were in use and when the dynamotors went to surplus they were never used. Consequently, the brushes are usually in decent condition. If you do purchase new brushes they will have to be contoured to fit the commutator closely. This can normally be accomplished with fine sandpaper that is placed around a wooden form that's the same diameter as the commutator. The goal is to have the brush surface perfectly match the shape of the commutator. This will reduce brush wear and eliminate "sparking."

The commutator segments should be bright and not exhibit too much grooving or wear. Light cleaning can be done with very fine sandpaper held against the segments while the armature is rotated by hand. The photo above shows how the commutators looked on this DY-12 before cleaning. Most of the time, the light cleaning is all that's needed. Again, the dynamotors were maintained in the military and afterwards seldom, if ever, used. Be sure to clean the grooves between each segment after the light cleaning. Sometimes conductive residue can get into the grooves and cause problems. Clean with denatured alcohol and an acid brush.  Photo left shows the +28vdc commutator after cleaning.

The ball bearings will normally need some attention. Again, while in the military, they were greased when the dynamotor was serviced, but since then, they have probably never even been inspected. You'll normally find that there is grease present but it has hardened to the point of becoming wax or even harder. Usually though, the old, hard grease will soften when saturated with WD-40. Use WD-40 as a solvent to spray the bearings. Use an acid brush or small stiff paint brush to work the WD-40 into the bearings. This should clean out most, if not all, of the old grease. The ball bearings should spin freely at this point. Photo below left shows the original grease before repacking.

Now, work new grease into the ball bearings. Don't use that old, stringy, yellow grease that the military used back in the 1940s (even if you could find it.) Use modern high temperature wheel bearing grease. This type of grease is easy to find at any place that sells auto parts and is usually transparent red. Use your thumb and fingers to "press" the new grease into the ball bearings until they are full. Replace the gaskets and covers. Be sure to clean and install any shims that adjust the thrust movement of the armature. Photo below right shows the bearing with new grease before the cover was reinstalled.

Since you've repacked the bearings, clean the commutators with alcohol again to make sure there's no grease on the segments. Replace the brushes and brush retaining caps. If you've marked the orientation and location, everything should go together easily and correctly. Install the end-bells. You might have to clean their mating surfaces for easier installation. Connect the dynamotor to a voltage source and to the ART-13 for a load. Upon switching on power and actuating the PTT on the ART-13, the dynamotor should rapidly come up to speed and power up the ART-13. The bearings should be running quietly,...well, as quiet as a large dynamotor runs anyway. If everything is correct, the ART-13 should produce a little over 100 watts output when running on a good condition dynamotor (that's powered by a PP-1104-C or similar power source.) When PPT is released the dynamotor should "coast" to a stop in a few seconds. This shows that the brushes are riding smoothly and the bearings have ample lubrication.

For more details on cable building and operating the ART-13 with a dynamotor go to "Operating the T-47/ART-13 with the DY-12 Dynamotor" further down this page


Basic Design Requirements for a Homebrew AC Operated Power Supply

General Information - Due to the difficulties involved in battery-dynamotor operation, most ART-13 users opt to build an AC operated power supply that provides +1150vdc @ 250mA, +400vdc @ 250mA and +28vdc @ 10 amps. There are several schematics available on the web and in various magazine articles, even in old surplus conversion handbooks. How elaborate the supply is depends on the desires and abilities of the builder. It is possible to connect a +750vdc power supply in series with the +400vdc power supply to create the +1150vdc. That's the way the +1150vdc was achieved in the dynamotors and it's perfectly okay to simulate this approach in an AC power supply. The advantage is the power transformers are much easier to find as are most of the other components necessary for that approach to the supply. The disadvantage is that the +400vdc supply has to carry double the current since it's in series with the +HV.

Many users want to increase the HV to have higher power output from the ART-13. Most ART-13 users feel it's safe to increase the HV to +1500vdc. At this level your power output can be around 175 watts. Some users run higher voltage without any problems. +1800vdc will result in about 200 watts output. Above this level though some audio distortion might be experienced. In fact, there have been reports that the screen tap on the modulation transformer may be responsible for slight audio distortion above +1300vdc +HV, though this is not typical. The 813 is rated for around +2200vdc and the 811s somewhat higher. Generally, if higher plate voltage is desired then separate +HV and +LV power supplies are used.

If plate voltages higher than +1150vdc are used, be aware that you might not be able to use the recommended military carbon microphones and achieve full modulation. This is primarily due to the fixed gain of the audio module (check value of R203 in audio module and use 4.7K for better C-mike gain.) Even though the plate voltage of the modulator tubes is at a higher level, the +LV voltage isn't and therefore not enough audio drive is available using stock military microphones. It is possible to increase the +LV about 10%, or up to around +440vdc and this will provide better audio response (in addition to some help in the grid drive to the PA.) Don't increase the +LV any higher than +450vdc. Use of an externally amplified microphone is usually necessary when running the ART-13 at higher plate voltages. However, this is very easy to accomplish using an Astatic TUG-8 amplified microphone stand.   >>>

>>>  The Plate Current meter operated with a 13.4 ohm WW and a 6.7 ohm WW resistive bridge that was installed in the dynamotor. Total Plate Current for the 813 and the two 811 tubes is being measured by routing the -HV through the shunts and the meter. Most AC power supply designs use separate +HV and +LV supplies which can then utilize a single 20 ohm WW shunt with the shunt connected to U/7 pin 2 (-HV) and to U/7 pin 9 (Meter positive) with pin 9 connected to Chassis. The Plate Current meter will read 200mA FS using a 20 ohm shunt. When increasing the +HV higher than about +1250vdc, it will be necessary to recalibrate the Plate Current meter for higher full scale capability. This is usually accomplished in the AC power supply design by using an adjustable Ohmite resistor to replace the fixed shunt.

The original bridge resistor in the dynamotor was a tapped 10W WW resistor but most AC Power Supply designs using separate +HV and +LV use a higher rated adjustable shunt resistor for increased reliability and protection of the Plate Current Meter. Most users adjust the value to have the Plate Current read 2X of the meter scale. The Grid Current and Battery Voltage functions are not affected by this resistor change - only the Plate Current. If series +HV and +LV supplies are utilized then two resistors should be used. From Pin 2 (-HV) to Pin 1 (+LV) a 13.4 ohm series load is used and from Pin 9 (Meter +) to Pin 1 (+LV) a 6.7 ohm series load is used. Pin 9 is not grounded or connected to chassis in this configuration. This hook-up duplicates what is found in the dynamotor.

How to provide the +28vdc at 10 amps is very easily accomplished by using modern, small, solid-state switching power supplies. These can be often found with current rating higher than 10 amps which will assure that you have sufficient current to operate the Autotune on the ART-13. Remember, in addition to the ART-13 tube filaments, relays and the Autotune motor, you are also going to be operating the two relays in the AC power supply with the +28vdc power supply section so extra current carrying capability is desirable. Anything 10 amps or higher will work fine. Another thing to remember is that modern switching power supplies are not like the ones designed and built two or three decades ago. Older "switchers" had excessive noise on the outputs while the modern (designed in the past several years) are noise-free and quiet in operation. Try to find a modern "switcher" and you won't have any problems. One more note, most +24vdc "switchers" will adjust up to +27 to +28vdc with no problem, so you don't have to look for a "28vdc" power supply. 24vdc "switchers" are easy to find and will adjust up just fine. 

The Vacuum Tube Rectifier Approach - It is up to the builder of the AC power supply to decide if they want to use vacuum tube rectifiers or to go solid state on the +LV and +HV. When opting for vacuum tubes remember, you will have to provide filament voltage for the rectifiers and, due to the nature of the ART-13's PTT system, this will require using separate filament transformers. You'll also have to provide tube sockets and the necessary sheet metal work to mount these pieces.

If mercury vapor (MV) rectifiers are used in the +HV, you could experience "flash-over" at sometime - always exciting! 866A MV tubes can be replaced with the 3B28 High Vacuum Rectifier tubes to avoid future problems. For the +400vdc, you'll have to use a 5U4GB and be sure it is the "GB" version since only that type has the current carrying specs necessary. You could use two 5R4G tubes for sufficient current capabilities but this will require one more socket, more sheet metal work, in addition to the increased filament current requirements. The 5U4GB will handle the current and voltage with just one tube. 

Though vacuum tube rectifiers are cool, going Solid State is much easier. No sockets, no filament transformers, no sheet metal work, etc. For the +HV, you can use replacement microwave oven diodes (NTE 517) that are rated at 15KV PIV. These diodes seem to work quite well in the +HV application. Reference the section below "Homebrewing an AC Operated Power Supply for the ART-13" for detailed information including schematics of both Solid State and Vacuum Tube Rectifier type supplies.

Construction Details -   ART-13 Power Supplies will have at least two large transformers for generating the +LV and +HV. Transformers will have a electromagnetic field surrounding them while in operation that varies the flux at 60Hz. Most transformers are shielded but some of the field is still present on frame type units. Potted transformers are the best of the shielded designs. Most power supply layouts will first separate the two supplies, the +LV and +HV, at opposite ends of the chassis. Orientation of the cores at opposite angles will also help reduce magnetic coupling. Use of a steel chassis will help to separate the control circuits from fields. Finally, a steel cabinet that is grounded to the chassis and to the ART-13 will help to reduce coupling problems. Note that since the ART-13 cabinet is entirely made out of aluminum, it offers little protection against low frequency magnetic coupling problems even though it is grounded. If an ART-13 AC power supply has no cabinet or an aluminum cabinet and it is placed close up next to the right side of the ART-13, the power transformers of the power supply are very close to the Audio Module with no protection against magnetic coupling. Likely some 60Hz hum will appear on the audio of the transmitter. An easy solution is to locate the power supply further away from the ART-13. However, if a steel cabinet is used in construction the magnetic coupling is shielded and the ART-13 can even be placed on top of the power supply with no magnetic coupling issues.

ART-13 Power Cable Construction - In addition to the power supply, a power cable will have to be built. At least one U/7 plug will be needed. The cable should have two 14 gauge wires, one 16 gauge HV wire and seven 18 gauge wires. I use 6000vdc rated test lead cable for the one +HV wire since physically it's not any larger than the 14 gauge wires. The test lead wire gives some added protection at +1500vdc or more. The cable should be wrapped with electrician's tape to keep the wires in place and then the entire cable should have a braided shield installed over it. This shield is important because it not only keeps RF out of the cable but also provides the chassis to chassis connection from the ART-13 to the AC power supply. This helps to distribute the ground returns and simulates the ART-13 to aircraft frame connections of the original installations. To make the shield I use a length of RG-8U coaxial cable and remove the outer jacket. Then push the shield together a little bit and the center conductor and dielectric can easily be removed. Then slide the shield over the ART-13 power cable and pull the braid tight. Finish by wrapping the shield with two layers of electrician's tape. The shield should be connected to the ground pins on each end of the cable. Usually about 60" to 72" is a good length for the cable. Longer cables will have more of a voltage drop on the high current wires. The cable can connect to a terminal strip on the power supply side to avoid having to buy both the U/7 connector and a U/7 box. These connectors sell for about $60 each.  >>>

>>>   Here are the connections to the 10 pins of the U/7 connector,...

Pin 1 = +LV, approximately +400vdc

Pin 2 = -HV, this is the minus return and is provided for the total Plate Current shunt function connected to the minus (-) of the Plate Current meter via the selector switch. If series +HV and +LV supplies are used then Pin 2 connects to Pin 1 (+LV) through a 13.4 ohm WW resistor. If separate +HV and +LV supplies are used then the -HV (pin 2) is connected to chassis through a 20 ohm WW shunt.

Pin 3 = +PTT line, this is approximately +28vdc with the PTT function actuated

Pin 4 and Pin 6 = +28vdc input (use separate wires to distribute the current load.) Generally, pin 6 provides voltage to the tube filaments and pin 4 provides voltage for the relays and Autotune.

Pin 5 = Chassis, Ground - Use a separate ground connection to the ART-13 case to help distribute the current load. The power cable shield should provide an excellent chassis to chassis connection between the transmitter and the power supply. This will help simulate the chassis-case connection to the aircraft frame that was part of the mounting system. It is also advisable to connect the ART-13 to the station ground by a wire connected to one of the case screws.

Pin 7 = ART-13 power on, this is a switched to chassis connection to actuate the +28vdc relay in the dynamotor (or homebrew AC PS) that provides a "switched on" condition at pins 4 and 6

Pin 8 = -PTT line, this is the chassis connection with the PTT function actuated

Pin 9 =  Positive (+) connection to Plate Current meter via the selector switch. This can be connected to Pin 5 or chassis if separate +HV and +LV power supplies are used along with a single 20 ohm shunt. If a series +HV and +LV are used (simulates dynamotor connections) then Pin 9 is connected to pin 1 (+LV) through a series resistor of approximately 6.7 ohms.

Pin 10 = +HV, high voltage for 813 and 811 plates (use HV test lead wire or similar)


Homebrewing an AC Operated Power Supply for the ART-13

Three ART-13 power supply approaches are presented here. The first two versions provide separate +HV and +LV supplies along with +28vdc supply. The first is a "Brute" of a power supply where space and weight are not a consideration but high plate voltage and stability are the primary goals. The second power supply, the "Hommage a le Valve," is a typical VT approach to building an ART-13 power supply that doesn't stress the transmitter, only providing +1400vdc for the +HV. This power supply is much smaller and only weighs about 75 pounds.  The last section provides details on how to build the "Dyna-Sim," or Dynamotor Simulator, that uses series +HV and +LV power supplies (aka "stacked" supplies.) This method allows the builder to use smaller, easier to find components and still provide about +1200vdc (or more) plate voltage. Schematics for all three types of AC power supplies are provided.

The Brute - I built the electronics portion of "The Brute" for KØDWC (who did all of the work on the mechanical portion) to use with his ART-13A with the idea of gaining maximum power output with massive components for "rock-solid" stability. This power supply consists of a huge 1760vac CT @ 500mA Plate Transformer using a Choke-input filter to provide about +1680vdc HV. A +400vdc power supply uses a dual section filter for low ripple. The +28vdc is provided by a Meanwell switching-type power supply rated at 13 amps. These are set to their maximum voltage output of +26.5vdc. The bottom section of the power supply contains most of the +1680vdc components. The top platform contains one of the HV chokes, the +400vdc and the +28vdc power supplies. PTT and Power ON relays along with the 100W bleeder resistor are also mounted underneath the top platform. All outputs and control lines are wired to a U/7 type box connector so that connection to the ART-13 requires a cable similar to the original dynamotor cable, that is, with U/7 plugs on each end. A screened cage covers the entire power supply for safety. Due to the weight of this "Brute," casters were added to the bottom and moving the unit around is actually quite easy.

+1680vdc - Features a very large plate transformer that easily will handle 500mA continuous duty. This results in a very stable +HV for the transmitter. Solid State Microwave Oven diodes (NTE517) are used for rectifiers and two 2500wvdc rated oil filled capacitors in combination with two large chokes make up the Choke-input filter. A large 40K 100W bleeder resistor is used on the output.

+400vdc - This supply uses a large power transformer rated at 200mA. Again, SS Microwave diodes are used (though not necessary) but this time a dual-section filter is used. This consists of three series combos of two 40uf electrolytic capacitors in series to get the working voltage up to 900vdc. 470K resistors are across each electrolytic to even out the voltage drop.

+26.5vdc - This is provided by a Solid State commercial power supply rated at 13Amps. This modern switching power supply has a cooling fan that changes speed depending on the current demand. Manufactured by Meanwell. All output wires must be shielded for potential RFI problems.

Relays - Two 28vdc relays provide "Power ON" function for the ART-13 and the Push-to-Talk function.

Fuses - All inputs and outputs are fused for full protection.

Meters - No meters are provided on the Brute

Pilot Lamps - These are vintage 120vac lamps. Amber indicates that the +28vdc power supply is turned ON. When the ART-13 is switched ON a relay actuates and connects +28vdc to the ART-13 U-7 plug. The Red lamp indicates that AC primary voltage is routed to the PTT relay and that +LV and +HV will be routed to the ART-13 when PTT is actuated.

Plate Current Meter Shunt - This is a large Ohmite 25 ohm pot rated at about 25W. It can be adjusted to 20 ohms for a 1X meter scaling or set to 1.5X or 2X if desired.

Cage - This large metal screened cover protects the user (or pets) from accidental contact with the +LV or +HV circuits. Since the "Brute" is designed to set on the floor, it is located far away from the ART-13 and no magnetic coupling issues will be experienced.

Hommage a le Valve - This is the first ART-13 power supply that I built. I decided to go tube rectifiers for the +HV and +LV. The +28vdc is provided by a very small Nemic-Lambda switching power supply. I didn't want to really push the T-47/ART-13, so I was shooting for about +1400vdc for the +HV. I happened to have a "parts set" that originally was a relatively small 813 transmitter. This piece of equipment provided the +HV iron and many smaller parts. This 813 transmitter was housed in an old S-47 Hallicrafters cabinet that was also utilized. I installed a "butch-plate" on the "stripped" 813 transmitter chassis and this became the new chassis for the power supply. Another "parts set" homebrew high-power audio amplifier supplied the +400vdc iron and a few more parts. All of the smaller parts like relays, meters, etc. came from the junk box. I decided to use a large terminal strip for the outputs on this power supply. This then allows building a cable that only uses one U/7 plug.

I decided that since 866A MV tubes were going to be used I should have a "viewing port" to watch the "blue glow" of the tubes. Full metering was also provided only because I happened to find a matching set of three meters in one of the junk boxes. A 5U4GB has to be used for the +400vdc due to that tube's rating being at a high enough current and operating voltage for that application. Since tube rectifiers were used, I provided the filament voltages with separate filament transformers. This allowed the tube rectifier filaments to be "on" at all times but to use the PTT from the ART-13 to apply the +HV and the +LV via the power transformers to the rectifier plates. This simulates the operation of the dynamotor starting up with actuation of the ART-13's PTT.

+1400vdc - Relatively small plate transformer salvaged from old homebrew 813 transmitter. 866A MV rectifiers utilizing a 2.5vac 10A filament transformer. Pi-filtered.

+400vdc - Power transformer from homebrew audio amplifier. 5U4GB rectifier. Dual section filter.

+28vdc - Nemic-Lambda +27.5vdc rated at 10Amps, a small switching power supply of modern design. Actually this power supply is a 24vdc power supply and is adjusted up to +27.5vdc using the voltage adjustment pot provided on the rear chassis of the unit. 40mv of ripple regardless of load. RF quiet. Even so, all output wires must be shielded for RFI quite operation.

Relays - Two 28vdc relays for ART-13 power ON and PTT function.

Fuses - Fully fused on all inputs and outputs

Pilot Lamps - High intensity clear LEDs provide illumination inside vintage "jewels." These LEDs were purchased at Radio Shack. When operating these LEDs on AC, a diode will be needed along with the appropriate load resistor. As seen below in the photo, the red and yellow lamps only illuminate when the power supply is providing +HV and +LV to the ART-13. The blue lamp indicates that the ART-13 is "ON" and ready to use. The left green lamp indicates that AC is applied to the +HV/+LV section and the rectifier filaments are powered. The right green lamp indicates that the +28vdc supply is "ON."

Meters - The +HV and +LV meters only indicate voltage when the ART-13 is in operation. The +28vdc meter indicates that voltage as supplied to the ART-13 and is in continuous operation while the power supply is "ON."

Plate Current Meter Shunt - I used a 40 ohm 25W Wire Wound potentiometer that had a 25 ohm 25 watt WW resistor in parallel with it. This allows easy adjustment to 1X, 1.5X or 2X of FS reading on the Plate Current meter. The excessive dissipation of the shunt is just a safety factor since this is the only path for -HV to chassis. Failure of this shunt would allow full -HV current to flow through the meter (which is not good.)

Cabinet - Hallicrafters S-47 painted black wrinkle finish. Tag found in the junk box. Since this cabinet is steel and is grounded, the ART-13 can set on top and there will be no 60Hz AC to audio chain magnetic coupling problems

Schematic for the Brute

By comparing the two schematics, it is obvious that going solid-state is a much easier approach to building an AC operated power supply to operate the ART-13

Schematic for Hommage a le Valve


The Dyna-Sim - "Dynamotor Simulator" - Series +HV and +LV Power Supplies

For many months now, every few weeks I've been switching in and out of the operating position one of my two ART-13 transmitters because only one AC power supply was available. After I finished the restoration of the ART-13A "Basket Case," I didn't design and build a power supply for it. This situation needed to change. I decided that I didn't want to go the huge, immoveable type of power supply but that I would rather design a power supply that was small and lightweight. I wasn't concerned about maximum power output since I had the "Hommage a le Valve" power supply that easily allowed running 150 watts output from the transmitter. This new power supply would be like the dynamotor in that two lower voltage supplies would be connected in series to provide the +HV and I would shoot for about +1150vdc as the dynamotor supplied.

The original dynamotor circuit provided +400vdc for the +LV and +750vdc (+HV) in series with the +LV to achieve +1150vdc plate voltage. A barometric pressure switch separated the two supplies above 25,000 feet altitude to prevent arc-over by reducing the plate voltage to +750vdc. It is very easy to use this same approach in designing an AC operated power supply, excluding the barometric pressure switch, of course. The advantages are that the components used will be rated at lower voltages which reduces expense and generally makes locating them easier. One thing to keep in mind is that the +LV supply must be able to handle not only its own current requirements but must also be able to carry the current required by the +HV since the negative return for the +HV is connected to the +LV and then to chassis. This means that the +LV will have to be capable of about 500mA maximum current. The original dynamotor spec for the +LV is 750mA but this is the dynamotor capability not the actual +LV current requirement of the ART-13.

To handle the additional current the +LV transformers are actually two identical transformers that are connected in parallel. When operating transformers in this manner they must be exactly the same,... identical. Also, their connections must be "phased." This means that primary and the secondary windings must be connected so the AC applied and the AC output are in phase in each transformer. This is easy to test ahead of the building and mark the primary and secondary windings so there will be no confusion at assembly time. I only used the parallel transformers because I didn't have a single 400-0-400vac that had enough current capacity for the +LV requirement. If you can find a 500mA rated transformer then going with the single, although large, transformer is much easier. Same reason for the parallel chokes in the +LV supply.

There are some changes that have to be made in the general design that allows for the proper operation of the Plate Current meter since the -HV is connected to +LV. This is basically done by providing a bridge circuit using a 13.4 ohm series load from -HV (negative meter connection) to pin 1 (+LV) and a 6.7 ohm series load from pin 1 (+LV) to pin 9 of U7 (positive meter connection.) This duplicates the circuit used in the original dynamotor. The advantage to this bridge resistor set up is that the Plate Current meter reads accurately regardless of the actual level of +HV and +LV as long as the ratio of +HV to +LV remains approximately 2:1 (actually, the ratio of +750 to +400 is 1.87:1 but the bridge resistor ratio is 2:1.)

Since a minimum of  +750vdc is used for +HV, the filter capacitors can be series-connected 100uf 450wvdc type electrolytics with 510K resistors across each cap to equalize the voltage drop across the series connections. Three capacitors are used resulting in a working voltage of about 1350vdc at a capacitance of about 33uf. Since we are using Pi-filtering, in an "unloaded" condition the +HV could soar to around +1035vdc.The extra "head-room" is protection in case the power supply is operated without a load. The same type of "head-room" is used in the +LV section, where the unloaded voltage could rise to around +600vdc. Using two series-connected 350wvdc electrolytics results in around +700vdc capability. In normal operation, the power supply design is such that the +HV and +LV are actuated with the PTT from the ART-13 which would also be in the powered-up condition thus presenting full load to both the +HV and +LV instantly. However, in some testing situations (or perhaps in an ART-13 failure mode) the power supply might be operated "lightly loaded" (or "unloaded") and this capacitor "hook-up" gives us the necessary head-room to survive this possibility without component damage to the power supply. 

Solid-state microwave oven type diodes can be used in both supplies connected as full-wave rectifiers. These diodes are type NTE517 rated at 15kv PIV. These diodes are relatively expensive at about $6.00 each. The advantage of SS diodes is higher output voltage from the power supplies.

To take advantage of the smaller size and lighter weight possibilities, a 24vdc 13 amp Meanwell Switching Power Supply is used for the +28vdc requirements. This supply can be adjusted up to +27.0vdc maximum which will provide sufficient voltage to operate the filaments, relays and the Autotune. Though the Meanwell PS is RFI quite as a +27.0vdc source for the ART-13, it can cause interference in receivers unless the cable from the power supply to the ART-13 is fully shielded. I've used this model Meanwell on two different ART-13 power supplies and there is no interference in either the transmitter operation or in the receiver being used. The Meanwell PS is approximately 2.5" x  4" x 8" and weighs about 3 lbs. This is the same type of PS that we used when building "The Brute" ART-13 power supply. The Meanwell PS is generally available on eBay for about $25 plus shipping.

I decided to build the Dyna-Sim into a BC-348 cabinet. This cabinet had been destroyed by a former owner who drilled out all of the pop rivets that mount the bottom plate which has all of the engagement pins for the shock mount. Rubber feet were installed to take the place of the engagement pins, thus ruining the cabinet for proper use with a BC-348 and FT-154 shock mount. The back of the cabinet had have a wide rectangular opening cut to provide access to the fuses, line cord and the output terminal strip. A round hole was also cut to provide ventilation for the fan in the Meanwell PS. The front panel is made from type of black hard plastic called delrin. Three panel meters are provided to allow constant monitoring of the output voltages during operation.     >>>

>>>  As with the "Hommage a le Valve" power supply, the only reason I used three meters is because I found three matching meters in the junk box. Setting up any DC current meter to act as a DC voltage reading meter is quite easy and only involves knowing the meter coil resistance, the meter full scale current requirement and then calculating a series dropping resistor based on the supply voltage to be measured versus the FS voltage scaling desired. For example, if the meter to be used is a 1mA FS DC Current meter and it is going to be used to measure the +400vdc and the FS DC voltage scaling desired is +1000vdc. The DCR of the meter coil in a 1MA FS meter is usually around 50 ohms (but measure it to be exact when actually doing your calculation.) Since the meter is 1mA FS, the total current through the series dropping resistor and the meter will be 1mA. The meter coil resistance is 50 ohms, so E = I/R indicates that the voltage drop across the meter at FS will be .00002vdc. FS DC voltage will be 1000vdc, so 1000 - .00002 = 999.99998 drop required in the series resistor. R=E/I so 999.99998/.001 = 999,999.98 ohms. You might as well use a 1 meg resistor. Dissipation equals I² x R = P or (.001 x .001) x 1,000,000 = 1.0 watt. 2X the dissipation is standard practice and allows the resistor to operate in the middle of its rating. So, a 1 meg ohm 2 watt resistor can be used and the 1mA DC Current meter will read accurately the +400vdc at .4mA on the scale. You can usually alter the actual meter scale so that "MILLIAMPS" is painted over and leave the "DC." If you have suitable "rub-on" lettering, you can add "VOLTS" to complete the meter transformation. To take advantage of the existing meter scale, the +HV meter actually indicates the +750vdc supply measured to -HV rather than measuring to chassis which would indicate +HV plus +LV, or the actual voltage applied to the 813 and two 811 plates. (I've been thinking lately that the +LV meter could be replaced with a +HV current meter. This would allow monitoring total +HV current and voltage simultaneously. Probably much more informative than monitoring the +LV that never changes. I'll update this section if I do that modification. - H.Rogers Apr 2013)

Two 24vdc relays are required for the PTT and Power On functions. The junk box turned up a very nice heavy-duty dual relay with 0.25" contacts. The problem was that the coils were for 115vac operation. Since these are solenoid coils, the operation doesn't really change whether AC or DC voltage is used. When using DCV on an ACV rated coil, you will have to greatly reduce the voltage. In testing the relay, it was found that good switching occurs with about 15vdc. A 150 ohm dropping resistor in series with the +27vdc supply provided around 18vdc to the relay and allowed fast, positive switching

A construction technique employed in the Dyna-Sim is the use of "component boards." The boards were made of 3/16" thick delrin and the terminals were made from 4-40FH brass screws secured with brass nuts. The use of brass allowed soldering directly to the terminal stud. Unfortunately, component boards require a lot of planning for proper layout and routing of the wiring (which is via a harness.) This prolongs the design phase and ends up with the project taking much longer to complete. If you're in a hurry then the use of standard tie points is easier and allows for quick construction. The upside of component boards is that the appearance of the wiring and construction looks like a professional job. See photos below of the finished Dyna-Sim.

+750vdc (+HV) - This is supplied by a 1475vac CT Plate transformer rated at .25A. Since no other windings are on the frame, this transformer is relatively small. Pi-filtered. Actual voltage is close to +900vdc under load. Total +HV is approximately +1300vdc.

+400vdc (+LV) - This is supplied by two identical parallel-connected 780vac CT Power Transformers and two identical parallel connected filter chokes. Actual voltage is around +440vdc under load. Total current available is 500mA. Pi-filtered.

+27.0vdc - This is provided by a Meanwell Switching Power Supply rated at 13A. Very small. Apparently not all Meanwell 24vdc power supply maximum voltage outputs are the same. Usually +26.5vdc is the specification for the maximum adjustment but this one adjusts to just over +27vdc. Fully shielded wires for RFI quite operation.

Relays, Fuses & Meters - Two 24vdc relays are used for PTT and Power On functions. The AC input and all outputs are fused. Three meters allow for constant monitoring of the voltages during operation.

Plate Current Meter Bridge Resistors - This is an original combination WW resistor from a junk DY-17A dynamotor base.

Pilot Lamps - High intensity LEDs with vintage-type jewels are used. Red = +HV, Yellow = +LV, Blue = ART-13 Pwr ON, Green = AC power ON to +28 supply and to +HV & +LV supplies.

Cabinet - Derelict BC-348 cabinet with black delrin front panel. The "cool" tags were donated by KØDWC and KE7MFW. Cabinet was painted with VHT Black Wrinkle Finish paint. 

NOTE ON CABINET: Since the BC-348 cabinet is aluminum (and the Dyna-Sim panel is delrin) and the case of the ART-13 is aluminum, no protection is provided for magnetic coupling from the non-potted transformers in the power supply. When installing the power supply be sure it is not placed directly next to the right side of the ART-13. Since this is where the ART-13 Audio Module is, very likely magnetic coupling will occur and cause some 60Hz hum to appear on the signal in the VOICE mode.

photo above: The Dyna-Sim ART-13 Power Supply in operation



Photo Top Left - The top of the chassis of the Dyna-Sim ART-13 Power Supply. The two identical transformers on the upper left are the parallel transformers for the +LV supply. To the lower right is the transformer and choke for the +HV supply. The upper right is the +27vdc 13A Meanwell Switching Power Supply. The component board on top of the chassis has the load resistors for the meters and for the three LEDs for Power On, +LV and +HV. Chassis dimensions are 16.5" x  8" x  3"

Photo Lower Left - Under the chassis upper left are the parallel chokes for the +LV. The left side component board is for +LV diode-filtering. Center is the PTT and Power On relay. Upper center are the relay load resistor board and the auxiliary +HV filter board. Right side is the +HV diode-filtering board and mounted on the side wall of the chassis is the Neutral Buss, AC LED Diode Board. Note the Ohmite resistor mounted vertically next to the fuses. This is the plate meter bridge resistors. 

Below is the schematic for the "Dyna-Sim."

Initial Testing of the Power Supply - After any one of these power supplies is built it will be necessary to perform some tests before actually connecting it to a transmitter. This will require attaching some "hefty" load resistors for the +LV and +HV supplies. The +28vdc doesn't require a load since the Meanwell is voltage regulated and remains constant regardless of the load. With the +28vdc operating check the operation of the two relays that operate the "Power ON" function and the PTT function. This will require using some test leads for the connections to simulate what the ART-13 does in operation. You can use a separate +28vdc bench power supply to actuate the PTT, otherwise, using a test lead connect PTT + (pin 3 U/7) to the +28vdc and ground pin 8 U/7 with a test lead to actuate the PTT.

The +HV and +LV will require calculating a suitable load resistor for each supply. By using the expected voltage as E and the amount of current drawn as I, then E/I=R, which will give you the resistance value for that amount of current to be supplied by either the +HV or the +LV supply. Use I²R=P to calculate the amount of watts the resistor will have to dissipate. You'll find that the load resistors must dissipate around 100 watts, so large wire wound "Ohmite-type" resistors are required. Use good clip leads to connect the load resistors to the output terminals. Apply the power supply AC voltage and actuate the PTT. This will apply AC to the +LV and +HV transformer primaries. Measure both the +HV and +LV to see what the actual voltage "under load" is. Let the power supply run for a few minutes and then deactuate the PTT and turn the power supply off. This checks the most important part of the power supply. Use about 225mA or so for the +LV load current and about 130mA for the +HV load current.

Once these tests have been performed, attach the U/7 connector to the ART-13 and power it up. If you are using the power supply with a known operational ART-13 that is already connected to an antenna, you should be able to do a test of the entire operation of the power supply and see how it works with the transmitter. If you are going to use the power supply to troubleshoot an unknown condition ART-13, then you might be blowing some fuses. That's why fuses are in the circuit - to protect your power supply. Use only the fuse current rating necessary for reliable operation in the fuse values you select. Fuses "blow" because of the relationship of their internal resistance versus the current flow through the fuse. IR=P and P (watts) is what blows the fuse. The voltage shown on the fuse is the design rating for the fuse structure and type of housing. It's the current change that "blows" the fuse since the circuit voltage and the fuse resistance remain constant (until the fuse "blows.") So the appropriate fuse current rating is just slightly higher than the normal current demand of the circuit being powered.

IMPORTANT NOTE ON THE MEANWELL POWER SUPPLY - I've never experienced any RFI noise problems with the Meanwell switching power supply when used with the ART-13 as the source of +28vdc at 10A. That being said, I've noticed that if the Meanwell is used to power up a receiver, for instance the R-392, fairly noisy operation will result. This situation was experienced when the power connecting wires from the Meanwell power supply to the receiver were unshielded. Although the receiver and the power supply were grounded, the connecting wire for +28vdc was unshielded and could thus radiate some RFI noise. I'm sure that the reason I don't have any receiving noise when using the ART-13 is because the Meanwell power supply is shielded within the homebrew power supply (HB PS) cabinet and is grounded to the chassis of the HB PS and the connecting cable from the HB PS to the ART-13 is fully shielded. So, when using the Meanwell on some DC operated gear you may find that if your connecting wires are unshielded you'll have some interference in the equipment or in nearby receivers. However, with a fully shielded cable that interference is eliminated.


ART-13 Restoration Hints and Suggestions

The Mechanical Stuff

The Autotune Mechanism - The Autotune is made up of four 360º rotation (single turn) modules and one 20 turn module. These modules are driven by a Line Shaft that has worm gears on it that mesh with the drive gears in the five modules. The line shaft is driven by a reversible direction motor that is controlled by a motor drive relay. Additionally, the Channel Selector switch works in conjunction with the motor driven (from module A,) rotating Selector Switch to determine which channel has been selected. Finally, there is a Forward Limit Switch and a Rear Limit Switch that reverse the direction of the motor and provide the stop function by removing a short circuit condition on the motor current resistor (when the cycle is completed, a small "locking" current flows through the motor windings.) The two limit switches that basically control the cycle are located on the 20 turn module since its operation requires the longest time to achieve its set point.

Important Note: Do not try to adjust the knobs of the Autotune section while the Locking Bars are tight. Anytime you want to adjust the settings of the individual control, first undo the Locking Bar and then make your adjustment. Then retighten the Locking Bar. If you make adjustments with the Locking Bar tight, you'll upset the presets for that channel and possibly all of the other channels too. You can also place the Channel Switch in MANUAL and let the Autotune cycle. Afterwards you can then manipulate all of the controls with the Locking Bars tight and you won't upset the presets.

As soon as you power-up the +28vdc line to the ART-13 the Autotune will begin to function if the Channel Selector switch position has changed since the last time the transmitter was in operation. The Autotune cycle first runs the five modules to a "zero" position and continues until the Forward Limit Switch is actuated which then reverses the motor direction. In this rotational direction each of the modules will lock in a preset condition determined by where the controls were "preset" for the particular channel selected. After all five controls have locked in position the motor continues to run until the Rear Limit Switch is actuated which stops the motor rotation by placing the current resistor in series with the motor windings. This method of stopping the motor was used to provide enough current to "lock" the motor in position, preventing the controls from being accidentally moved by vibration or other methods. The entire Autotune cycle usually takes about 25 seconds to complete. When completed the PTT line and the Keying relay operation are returned to functionability and the transmitter can be put into operation.

Quick Test - A quick test of the Autotune can be accomplished by just providing +28vdc at about 10 Amps (this is the filament load plus the Autotune load, which is about 1 Amp while running.) Connect the power supply to pins 4 and 6 for the positive and pin 5 for the negative. You should use at least 16 gauge wire, 14 gauge is better. Switch on the power supply and the Autotune should start its cycle. If it doesn't, change the channel. If everything is okay the cycle should complete in 25 seconds and the motor will stop. Change the channel and the cycle should start again and complete in 25 seconds. This quick test shows that most of the Autotune is working. It will probably need lubrication and preset adjustment. 

Lubricating the Autotune Mechanism - The Line Shaft runs in bronze sleeve bearings and in ball bearings at each end. These bearings should be given a drop or two of light weight oil, 10W is good, something like sewing machine oil. Each module is driven by a worm gear that is installed on the Line Shaft. All of these worm gears should be coated lightly with light weight grease using a long handled paint brush. Each of the gears associated with each module can also be lightly coated in the same manner. Use a drop of machine oil on each of the bearings on the rotating gears. Use oil sparingly on the chain drive and don't stand in front of it during operation with the cover off after lubrication - you'll end up with oil all over the front of your shirt! (Yes, I've done it.)

Common Autotune Problems - Since the Autotune cycle controls the PTT line and the Keying relay operation, if there are problems with the Autotune, you won't be able to run the transmitter. Most of the time, the Autotune mechanisms are still in good condition because they were well protected by the front cover which even has felt seals around each opening to keep out dirt and dust. 

If the ART-13 you are inspecting to purchase has been disassembled and the front Autotune cover removed or left off, be very wary of the transmitter. The Autotune is difficult to work on if complete disassembly is required. Look for a transmitter that is complete and shows no indications of having been a "parts set" at some time past.

That being said, the most common problems with the Autotune involve the limit switches. The Forward Limit switch is mounted on the extreme right side-front of the 20 turn module and can easily be hit or bent with careless handling of the transmitter with the front cover off. The Rear Limit switch is a "rocker" type switch that is very, very delicate and if damaged it is difficult to get it to work correctly again. Fortunately, it is further back in the module and a little better protected from damage.  

If the Forward or Rear Limit switches aren't making good contact it will cause the Autotune to operate to "zero" position and then it will just set there with the motor continuing to run. With the Forward switch it is very simple to carefully bend the arm so that the rotating screw-driven actuator arm just opens the switch at the "limit position."

Opening the Forward Limit switch momentarily will reverse the motor relay position and reverse the direction of the motor so that the "preset" operation of the Autotune cycle can proceed. The Rear Limit switch has a spring-loaded contact that relies on a longer flex arm with a fiber button as the mechanical contact. Be careful if you have a mechanical problem with the Rear Limit switch. Very minor adjustments are all that should be required if it doesn't actuate. Bending of the arms should be avoided. Most problems with the Rear Limit switch are caused by contamination or dirt and not the mechanical adjustment of the switch arms.

Synchronization Problems - Sometimes the Autotune presets are not where some of the individual modules end up stopping. Most of the time this is dirt or contamination in the particular module's clutch. Try re-setting the preset and operating the Autotune cycle several times. Usually each time the module will stop closer and closer to the preset point. The operation seems to clean the clutch which results in accurate preset response. Sometimes the selector disks are not in the proper location to allow the pawl to drop into the slot and stop the control. Inspection of the module while in operation can confirm if this is what is happening. To correct, loosen the lock bar and rotate the particular selector disk to a position where the pawl can drop correctly, then tighten the locking bar.

Sometimes one or two modules will always operate to the end limit on a particular channel. Check the springs on the pawls to see if one of the springs has is not in its proper slot. Sometimes these springs become caught in the selector disks and will get bent. This is uncommon but it depends on how badly the particular ART-13 was treated in the past.

If you have an insolvable problem with one or more of the modules, they are easy to replace, but you'll have to re-synchronize the other modules to the new module. To remove a module first take the front cover off. Then remove the locking bar and the knob. Remove the knob backing plate and you now have access to the two slotted head screws that mount the upper part of the module. Remove these two screws and the lower Philipp's Head mounting screw. If you are removing the Antenna/Loading modules, you'll have to remove the screws that mount the phone jack bar to these modules. The bar only has to be dismounted and placed slightly out of the way to remove the module. The module engages the worm gear of the main shaft and has a spline drive socket at the rear that drives the particular control. Install the new module and replace the screws in reverse order.

Details on knob and module synchronization follow in the next section.

photo above
: PA Tuning and Loading section of the Autotune. These modules are single turn, 360º rotation, driven by the line shaft. Between the two left-most modules is the motor drive relay. Note how the phone jack bar mounts to these three modules.

photo above: The motor drive for the Autotune. The chain drives the line shaft mounted at the back of the Autotune unit.

photo above: The VFO section of the Autotune. The rightside module is the 20 turn unit. Forward and reverse limit switchs are on the far right.

Synchronizing the Autotune Knobs - If you have to remove the five large knobs you'll find that there is no obvious shaft flat or other indicator of how the knob position relates to the shaft position. Fortunately, all of the controls have mechanical stops at both ends of rotation. First set all of the controls fully CCW (be sure to loosen the locking bars.) Set the knob positions as follows:

A - Set shaft fully CCW and set knob to slightly before the triangle #1. Remember, all of the set screws require a Bristol wrench.

B - Rotate shaft fully CCW. Be sure that the small turns counter is at zero and at the mechanical stop. Then set the large knob to zero.

C - Set shaft fully CCW and set knob in the middle between triangle #1 and triangle #13 (verify that the antenna loading and tuning circuit contacts "make and break" when the knob triangles are exactly on the peak of the triangle. Triangle #5 is a good "test" position for checking knob synchronization.)

D - Set shaft fully CCW to stop and set knob in the middle of the non-scaled portion of the skirt (it will look like it's upside-down)

E - Set shaft fully CCW to stop and set to 0 on 100-0 scale

Tighten the locking bars and actuate an Autotune cycle. Since the knobs are already at zero, the knobs shouldn't turn until the forward cycle begins. Confirm that the controls stop correctly. Specifically, B should stop on a triangle, as should C. In fact, C must always be exactly on the peak of the triangle for each stop (once the knob is synchronized to the shaft.) This control also operates some finger contacts that are part of the antenna loading and tuning. If the setting of C is not exactly on the "peak" of the triangle these contacts may not be correctly actuated and the transmitter will not have any output or show any grid current. Also, confirm that D stops in the scaled portion of the knob.

Synchronizing the Modules - If you have to replace a module or if you've removed a module for some reason, you'll now have to synchronize the newly installed module to the rest of the Autotune modules. The procedure in the manual is difficult to understand because it references all synchronization to the A module since it isn't adjustable (because it drives the channel selector switch.) Most of the time you're going to have one of the single-turn modules that isn't in sync with the other single-turn modules. To do the synchronizing, you'll need a way to manually move the Line Shaft via the slotted and tapped hole (4-40) on the right-hand side of the Line Shaft. Originally, the spare parts kit contained a crank that was for that purpose but nowadays the cranks are next to impossible to find. Some technicians use a screwdriver or a blade bit installed in a power driver. If you choose this option, you'll have to be very careful not to damage the slot in the Line Shaft.

It's fairly easy to use a power driver (like a Makita) with a blade bit to position the Line Shaft and not damage the slot in the end of the shaft. Just be careful and make sure that the bit fits tight in the slot. You're going to be rotating the Line Shaft in a counterclockwise rotation.

To synchronize any C, D or E module to the A and B modules just remember to consider that all four sync'd modules should be considered as a single module and it is going to be necessary to sync them with the remaining module (that is out of sync.)

You'll have to disable the out of sync module by loosening the cam drum collar set screws and sliding the collar down the shaft. This allows the selector clutch drum to move but not move the cam drum. See which channel the out of sync module is set to by observing the spring and pawl drop. Now rotate the Line Shaft in the counterclockwise direction noting that the springs and pawls all drop simultaneously on the "in sync" modules. When you are one channel before the channel desired stop using the power driver for rotation and switch over to a regular screwdriver. This is to allow the next sequence to proceed slow enough to control. As you approach the correct Line Shaft position, you'll see one spring-pawl slightly lift and then the next channel's spring-pawl drop into place. Stop rotating the Line Shaft at this position. Now check to make sure that the out of sync module is also in the proper channel with the pawl dropped into position. Slide the cam drum collar on the "formerly" out of sync module back up into position and rotate it with your fingers very slowly counterclockwise. You'll feel a point where there is some noticeable resistance to the rotation, which is the drive pin coming into position. Tighten the collar set screws at this point. You may be only able to tighten one of the set screws but this is sufficient until rotation of the Autotune brings the other set screw into position. Test the synchronization by rotating the Line Shaft counterclockwise with the power driver. Each spring-pawl should drop into position simultaneously. No more than a quarter of a turn of the shaft should be necessary for all of the spring-pawls to drop into position - usually it's much closer than that.

Now, do a channel-select Autotune cycle to test that all of the modules are synchronized. Set up the presets on channel one, then proceed to channel two and then check that if returned to channel one, all of the modules select the proper preset. You can now do all of the presets for all of the channels, that is, if your ART-13 is ready to go into operation.

Photo A

Photo A: This shows the A module which drives the rotating Channel Selector switch located behind the module. This switch rotates until it is in the same position as the front panel Channel Selector switch.

Photo B: This is a close up of a single turn module showing the cam drum. This is where part of the pawl drops into when a channel is selected. Also, the front part of the pawl drops into the slot in the channel locking rings on the clutch drum which determines the preset.

Photo C: This close up shows the cam drum collar which must be loosened and dropped down the shaft to disable the drive on an individual module for synchronization. The collar has a stop inside that couples a drive pin from the gear above. The drive pin couples to the collar stop and then, since the collar is set screw coupled to the cam drum shaft, turns it.

Photo B (left)

Photo C (above)

Refurbishing the Cosmetics

Reconditioning the Knobs, Dials, Locking Bars and Stop Plates The five large knobs are bakelite with a brass hub. The set screws require a Bristol wrench to loosen. These large knobs project out somewhat and therefore many times they are found chipped. If the knob is chipped, an original must be found to replace it. These large knobs sometimes are found with the white fill paint partially missing and when cleaning is attempted, more of the white fill paint falls off. These knobs are easy to recondition by first removing them and then soaking them in a hot soapy water bath for about one hour. Use a fairly stiff, brass bristle brush (toothbrush size) and be sure that the brush bristles are very straight like a new brush. Brush away towards the edge of the knob to clean the flutes. Don't be real aggressive but go around the fluted section of the knob twice with the brass brush to remove all of the finger grunge. Clean the skirt of the knob with a regular toothbrush. You'll probably find that most of the white fill paint will be removed in this cleaning. Dry the knobs and they will be ready for a new fill paint. 

 Don't use "White" paint or lacquer-stik for the fill. This will be way, way too bright and will look terrible. Use Artist's Acrylic paint that is available from most Hobby or Art Stores. Mix white, light brown (raw sienna) and just a little black. You're trying to get a color that looks like a manila folder,...kind of beige. Though it looks too dark when you're mixing it, when you put it on a black bakelite knob, it will look aged white. Paint the entire skirt of the knob and give the paint about one minute to set. >>>

>>> Next, use damped paper towel pieces that are about two inches square and folded to wipe of the excess paint. Use Glass Plus to damped the paper towel sections as this removes the paint much better than water. Do a small section and then discard the towel - do not try to wipe more of the paint with the same towel as you'll just spread the paint around instead of removing it. Each wipe use a new damp paper towel. As you get nearly all of the paint off, you'll notice the nomenclature looks really great. Now, be careful and just use a very light touch to remove the remaining paint. Normally, I have to do this application twice to get the knob to look first-class and original. You don't have to wait to apply the second fill. Once the knob is finished, set it aside and let the fill paint dry overnight before reinstalling the knob.

The smaller switch knobs have an index line that has the white fill paint. Recondition these knobs using the same procedure as the larger knobs.

The locking bars and locking bar stop plates are often chipped and might have some corrosion. They are very easy to repaint. I first strip the old paint. You will then see all of the defects that were under the paint. Corrosion is common but can easily be removed with 400 grit aluminum oxide paper. Buff with 0000 steel wool. You don't need a primer but be sure to wash the pieces using lacquer thinner before painting. Mount the locking bars on a piece of cardboard so the paint won't get on the back of the bar or on the threaded shaft. I use nitrocellulose black lacquer and apply several coats to the locking bars. The stop plates only need a couple of coats. Let the paint dry overnight and then use lacquer rubbing compound to smooth the finish and then buff. The locking bars and stop plates will look original.

Reconditioning the Front Panel and Cabinet Paint - Since the front panel nomenclature is silk-screened, a total repaint of the front panel sections is not possible. Instead you'll have to use the "touch-up" method. I use Artist's Acrylic "Mars Black" paint in a tube. This color is very close to the original black wrinkle finish on the ART-13. If dealing with the normal dings, flakes and scratches, the paint can be used from the tube and applied with a Q-tip. Rolling the Q-tip will impart a texture to the touch-up that looks close to the wrinkle finish. This paint does dry flat with no gloss. On small areas this usually isn't a problem. 

For larger areas you'll have to use VHT Hi-Temp Black Wrinkle Finish (available at O'Reilly stores) applied thickly with a brush. Spray some of the paint into a small cup and then use a brush to paint two fairly thick coats to the area. Let the paint set for a couple of minutes and then use a heat gun to "force" the wrinkle. Don't use too much heat or the paint will "gloss" and not match as well.

It's also possible to "touch up" using thinned nitrocellulose lacquer using a brush. Once all of the chips and scrapes are covered then use 10W oil (like "3 in 1" oil) on a cotton pad and rub the entire panel area with oil. The touch-ups will blend into the oil-reconditioned wrinkle finish and seem to disappear. However, if the touch-up area is too large then it will show as a "glossy area." Remember though, when the military reconditioned panels and cabinets, many times they just "touched up" using gloss black lacquer. We've all seen it on original gear, so don't be too concerned that some gloss touch-ups show.>>>

>>> Large areas such at the top lid can be conditioned by using an Acrylic "wash." This is a very thin mix of Mars Black and water. The mix should be about as thin as water but still have some paint in it. This mixture can be brushed on the top lid and the excess water "dabbed off" with a cloth - don't use paper towels as they leave lint and small pieces of paper towel behind in the paint. A cloth towel works best. When dry, the top lid will look even with no chips or scratches showing. It will be "flat" and not glossy but it will look better than a scratched up lid.  

Another method is to use thinned nitrocellulose black lacquer applied with a flat cotton pad. Use several cotton pads and saturate them with the thinned lacquer then rub down the entire lid. Be sure to wear nitrile gloves when handling the saturated pads. Since the lacquer is so thin, it covers a lot of area and dries rapidly. When finished the wrinkle finish will look in good condition and original. Be sure you've touched-up all of the nicks and scratches with lacquer before doing this thinned-lacquer rub down.

It is possible to use the VHT Hi-Temp BWF on many of the panels that comprise the cabinet but matching becomes a problem. Wherever there is silk-screening, the spray paint can't be used (except for touch-up.) Whether you can use the spray wrinkle finish to paint the lid or some of the panels will depend on the overall condition of the front panels. Be aware the painting the top lid is a very large area and very, very difficult to paint with wrinkle finish and not have "stripes" - areas that show the spray pattern. Try to spray at least four heavy coats with each coat applied at a different angles. This is the best way to avoid the "stripes." After the new paint has set for about a week, you can apply a matching wash of Mars Black to get the top to more closely match the rest of the transmitter.


T-47A/ART-13 "Basket Case" Restoration

This example of the restoration process features a really awful condition T47A/ART-13 (aka: AN/ART-13A) that was part of a trade-deal. Missing parts, extensively disassembled and cosmetic condition issues make this an excellent example to illustrate the types of problems involved with the restoration of "Basket Case" projects - and, perhaps, why to avoid them. 

The Big Trade - The photo to the right shows the USAAF T47A/ART-13 that I got in a trade. The fact that it was almost completely disassembled didn't matter since it was initially considered just a "parts set" to use for the restoration of another nearly complete US Navy Collins T-47/ART-13 that was also included in the trade. I know, want the story about the trade, right?

I got an e-mail offering two "rough" ART-13 transmitters, a "nice" BC-312 receiver and an "okay" BC-344 receiver plus several boxes of military radio parts in trade for audio gear or a tube tester. After a couple of e-mails we settled on trading a nice, working Hickok 600A tube tester and a "needs restoration" HP-712A power supply for a "load" of military gear that included the two transmitters and the two receivers. Photos were sent both ways and we both knew the condition of everything involved in the trade. A quick daytrip to Lafayette, California resulted in dropping off the tube tester along with the HP power supply and coming back home with my Subaru Outback packed full of military equipment and parts.

First Things First - The first project was to restore and get operational the Navy T-47/ART-13. This project took a about seven weeks to complete, which included designing and building a suitable power supply for the transmitter. I began using this T-47/ART-13 a lot and really enjoyed operating it. I didn't really consider even looking at the other ART-13 transmitter because it was a "basket case" and only a source of parts. Then, a few months later, fellow ART-13 enthusiast, W7MS, happened to mention "on the air" that he had a second ART-13 in storage that was his "hanger queen." This got me thinking that I probably could take my "parts set" and put it together enough to be a "hanger queen" that would be "for display only"  in the Western Historic Radio Museum (the museum I had in Virginia City, Nevada 1993-2012.) Functionability wasn't the goal, just a fairly complete, reasonably good-looking ART-13 for a museum display.

photo above: The ART-13A as I got it from the "Big Trade." Note that some of the sheet metal is setting beside the transmitter chassis 

photo above: The ART-13A after the "parts hunt" located most of the missing parts.

The Parts Hunt - As I searched for the parts I was finding boxes that had been picked up at the Big Trade but that I hadn't really looked in carefully. Looking through four large boxes turned up all of the sheet metal parts. I looked through more of the smaller boxes and plastic bags finding nearly all of the components that were missing. I began to think this project might progress from "hanger queen" to "restore and get it operational." After a thorough search I ended up with a pile of parts that looked like the photo to the left. In the photo, all of the sheet metal parts were just setting in place, so I could see that I had all of the pieces. Note that the combination bottom cover and shock mount rails isn't even in place but is leaning up against the side of the transmitter.

No amount of searching could find these missing parts: R-121, R123 and R-124. These are the wire wound resistors that are located in the rear compartment with the 811s and the 813. Additionally, the rear triangular bracket that supports the side panel for the blank panel couldn't be found. The MCW/FCI module and the Audio module "remains" had been sometime in the past totally disassembled for parts and I could only find the chassis and a few parts to those units. Also, the multimeter was unusable due to a broken glass that long ago had allowed the meter needle to become broken. Everything else that had been removed from the transmitter I was able to find in the various boxes of parts. This meant the transmitter was about 95% complete, just mostly disassembled.

In my "junk boxes" had two spare MCW/FCI modules so that wasn't a problem. KØDWC supplied the triangular bracket by giving me an entire blank panel assembly. I purchased an Audio module off of e-Bay. The meter and the wire wound resistors were obtained from Fair Radio Sales. So now, on to the restoration work.

Unusual Reassembly - The most difficult to repair damage was the three flexible plate cap connections (E-109B) for the 837 VFO tube and the two 1625 multiplier tubes. These consist of a flex connection and a brass tube that is soldered to a stud that is mounted through a pair of ceramic standoffs (top and underneath the chassis.) These three connections were "snapped" off leaving the stud inside the brass tube and a flush threaded rod with a nut on top of the insulator. After trying to drill out, tap and other methods that didn't work, I decided that I should solder a flange to the brass rod and then sweat-solder that to the nut on top of the insulator. This worked quite well and seems pretty strong.

To reconnect the large buss wire connections for the LF relay (K-105) and the Antenna push connectors I made brass sleeves out of shim material. These cylindrical sleeves were fitted to the cut buss wires and then soldered. The buss wires had to be re-tinned first and it does take quite a bit of solder to fill this kind of splice. The benefit is that it's a really strong joint and it looks like a professional repair job. See photo right.

The Interlock switch had the housing broken. Fortunately, it was possible to use epoxy to repair the housing and get the switch working again. Also, the mounting for the plate blocking capacitor used a pair of fiber screws into the ceramic standoffs and since one of the fiber screws was broken, I repaired the mount using epoxy.

A Wiring Error? - During the reassembly of the meter/switch panel I had to re-install the meter shunts and loads that are mounted with a long screw to a projecting tab that is on the back side of the right side inner panel. In checking the wire locations versus the schematic I discovered that the Meter switch had a wiring error. This was INCREDIBLE since it meant that the positions for Grid Current and Battery Voltage couldn't have worked. I used the wiring diagram (not the schematic) to confirm this was indeed an error. I think this must have been a later error done during a repair cycle that replaced the meter switch. It's likely that the transmitter didn't pass one of its tests after the rebuild and was set aside for a later checkout and repair cycle that was never done. The wiring error might have happened at SAAMA. The San Antonio Air Materiel Area (Kelly AFB,) performed extensive aircraft repair and repair of all aircraft equipment from 1947 up to 1974. This ART-13A has a SAAMA stamp for MFP application dated 15 Sept.1954. It's likely this ART-13 never made it out of the repair depot and was sold as surplus at some later date. The error was the interchange of two wires going to the Meter switch that introduced a conflict between the Grid Current and Battery Voltage. After switching the two wire positions, the meter then read Battery Voltage and Grid Current correctly. It's unlikely that this problem would have gone unnoticed, so why it wasn't corrected at SAAMA is a mystery. The photo left shows the SAAMA MFP stamp on the chassis.
Replica Calibration Book Pocket - The Calibration Book pocket was missing from this ART-13A. It appeared like the rivets were aggressively pulled out since the metal was slightly distorted. I took measurements from the USN T-47 that had its original book pocket and had a replica made at a local sheet metal shop. I had to add the curved cut-out and the edge treatment since this would have complicated the project for the metal shop. Once I had the piece shaped correctly, I had to remove the Autotune cover so I could accurately measure where the mounting holes had to be drilled. Also, there was some "body work" necessary to get the holes in the cover cleaned up. A close inspection of the original book pocket revealed that the inside was painted gloss black and the exterior was black wrinkle. The original wrinkle finish paint was a two part process that used a catalyst sprayed onto nitrocellulose lacquer to activate the wrinkle by baking in an oven. It's normal for older sheet metal pieces to be gloss on one side and wrinkle on the other. I painted the pocket with gloss black lacquer on the inside and Krylon Black Wrinkle Finish on the exterior. The original book pocket was mounted with round head rivets. Fortunately, I had the same kind of rivets in one of the parts drawers around here. The rivets are a tight fit and when the shaft part is deformed it pulls the mounting flange tight. The three photos below show the various stages of making the replica book pocket and the larger photo to the right shows the pocket mounted on the ART-13A. I still need to make the replica plastic tubing covered chain that attaches the book to the book pocket. A small hole at the lower right front corner of the pocket has a rivet/washer combination that holds the one end of the chain and a lanyard ring attaches the chain to the book binder ring. See updated photo at the end of this section showing the book, chain and ring installation.

Cosmetics - As can be seen in the "before" photo above, the panels did have some aluminum corrosion that was "popping" through the paint. I used the method described in the restoration section above to touch up the panels. This ended up with a combination of touch up and then using the "wash" technique. This resulted in the panels looking kind of flat but even and with some wrinkle to the finish. See the "after" photos below.

Since so much of this ART-13A was disassembled and parts were obtained from other transmitters to complete its assembly, the distinctive "gold" color of the MFP coating had to be applied to many parts. Probably the most difficult to match was the replacement Audio Module since this was a large piece that didn't have any MFP coating when obtained. Fortunately, I had a few parts from the original Audio Module to see just how much MFP was on it.

Quite a few years ago, I had some yellow-tinted nitrocellulose lacquer mixed for me. This is very close to what MFP was except it doesn't contain a fungicide or that distinctive MFP odor (darn.) I thinned this yellow lacquer down using clear lacquer and lacquer thinner to get the correct "look" of the MFP when sprayed onto the Audio Module. >>>

>>>  All of the other pieces that needed to be MFP coated were small - like screw heads and nuts, solder joints, sheet metal edges, etc. This was applied with a small paint brush direct from the tinted lacquer can. Looking at the finished chassis photo below shows the final appearance.

A new Settings Chart was necessary and an excellent one can be down loaded from BAMA. Just print it out on heavy manila paper and it will look original. New plastic for the chart can be found many places. I salvaged the plastic from a cheap picture frame.

Final Missing Parts Installation - The large wire-wound resistors, R-121, R-123 and R-124, were obtained from Fair Radio Sales. Luckily, when the originals were removed the wire must have been cut close to the resistor terminals because I did have enough wire left for the connections to the new replacement resistors. These large wire-wounds mount with an aluminum stud that is threaded on each end. The stud is mounted to the chassis with a screw and lock washer from underneath the chassis. Then several mica washers are placed over the stud and next to the chassis. Then the resistor is placed over the stud and secured with several more mica washers, a flat steel washer, a lock washer and finally a screw. Without R-121, you can't do any real "voltage on" testing because the +28vdc to the filaments is routed through this 0.8 ohm 50 watt resistor first. With the installation of these resistors the filament circuit is complete and testing can begin.

Testing - I tested both the MCW/FCI module and the Audio module by plugging them into my working Navy T-47/ART-13 to confirm they were operational units. The MCW/FCI module worked fine but the Audio module needed extensive repair (what else can you expect from an eBay purchase?) Two resistors had to be replaced. The audio input resistor had overheated and the value changed along with burning off part of the color code paint. The carbon mike Z load resistor had been changed from the original value of 15K to 4.7K (a common upgrade found in later modules that increases the mike bias for better response from typical carbon mikes.) I reinstalled a 15K resistor (just to be original.) A quick operational check showed that I still had some distortion that resulted in "harsh" sounding audio. The problem was caused by a defective coupling capacitor between the 12SJ7 plate and the 6V6 grid (C-204.) Since this was one of a "stack" of three molded capacitors (and one other capacitor already had broken mounting tabs,) I went ahead and replaced all three caps with SBE Orange Drops. Additionally, it was noted that the Jones plug was partially coming apart due to a bent over tab not holding the back plate in place. After several attempts to remount the back using the tab, I finally had to resort to a combination of epoxy and the tab to hold the backing plate in position. After these repairs, the Audio module output sounded great.

Pre-Testing - During the re-assembly of this ART-13A most of the sections that were affected by the disassembly were tested. A thorough inspection is necessary before powering up any transmitter. All components that could be tested with a DMM were given a cursory test. Be sure to test the Plate Blocking capacitor for shorts since this condition would allow for full +HV to be on the antenna system. All tubes are tested except for the 813 which can be given a quick filament continuity test and a quick shorts test with a DMM. Clean all the ceramic insulators.

Initially, I just connect +28vdc and make sure all of the low voltage circuits work. This test turned up a problem with the Autotune. Through the system would motor drive to the zero position it just remained at zero and would not continue onto the presets on any channel selected. Since the Autotune essentially wouldn't shut off, the transmitter couldn't be tested further until this problem was fixed.

Problem Details

Autotune Problem - I guess this transmitter was pretty much a basket case for quite sometime and the front cover was off of the Autotune mechanism. At that time the Forward Limit switch was hit or bent enough that it wouldn't open when the actuator arm contacted it. Momentary breaking of the contact would cause the Autotune to complete its cycle. I bent the contact arm just enough so that the contact would open at the Forward limit position and reverse the motor to complete the cycle. This got the Autotune working correctly.

+HV and +LV Test - When everything looked ready, I decided to go ahead with a full test. With the +28vdc on operation was normal and I allowed the tubes to warm up. After a few minutes, I switched to TUNE and pressed the THROTTLE SWITCH (T.S. jack - a remote PTT line.) This resulted in the immediate blowing of three fuses in my power supply. Two fuses were the primary fuses to the +HV and +LV transformers and one fuse was the +HV output. Since my power supply is fully fused in every input and output, no damage occurred there but certainly something was wrong the the ART-13A.

Problem One - The PTT line was grounded. This caused most of the problems involving the +400vdc. I traced the source of the problem to a solder bridge that I created when reinstalling K-104 - oops. Removal of the solder bridge cleared the PTT problem and the ART-13 would now operate and not blow the +400vdc fuse in the power supply.

Problem Two - The +1400vdc continued to blow both the transformer primary fuse and the output fuse in the power supply. A close inspection of the 813 tube socket revealed a burnt R-112, a 47 ohm 1 watt carbon resistor acting as a screen load. I replaced R-112 with an NOS resistor but wasn't too confident that it was causing the problem. I decided to also replace the old National Union 813 I had been using with an NOS Sylvania 813. These two changes got the +1400vdc and the transmitter operational and working fine.

The Initial Shake Down Test - This test used my homebrew power supply that I normally use to power the Navy T-47/ART-13 to power this T-47A/ART-13 version. This supply provides about +1400vdc for the +HV and results in about 160 watts output with the Navy transmitter. With the NOS Sylvania 813, this ART-13A had a somewhat higher output power running around 190 watts. I decided to use a variable capacitor (instead of a fixed value capacitor) for the Auxiliary Condenser so I could load the antenna exactly. This setup allowed me to adjust the ART-13A for about 200mA total plate current and have a power output of about 145 watts. This allows the transmitter to run in a very stable manner since the power supply current carrying capabilities are not "pushed" and the +1400vdc plate voltage remains fairly constant during operation. The reduced power also allows for easy 100% modulation without "loading down" the plate supply (which was what was happening at 190 watts output.) Monitoring with earphones listening on an RCA CR-88A (with no antenna connected) sounded great. Watching the oscilloscope looked great. The next test was to call up KØDWC and have him listen to the signal at his station (next block up the street.) With this set-up, I can also hear what Chuck hears via the telephone connection. Finally, a true "On the Air" test with the Sunday morning Vintage Military Radio net was next (3974KC - 8AM Pacific Time.) The "On the Air" test was successful and the reports that came back were all positive.

photo left: The chassis of ART-13A sn 417ACG after restoration. Note the distinctive "gold" appearance from the MFP coating.

CW Mode Inoperative - This problem was actually found after I had used the ART-13A "on the air" in the VOICE mode. I decided to try some 40M CW with the ART-13A and after loading up in the VOICE mode, I switched to CW. When switching to the CW mode, the transmitter should show plate idling current and when depressing the key the plate current should increase up to slightly less than the VOICE plate current (since you don't have the Modulator idling current.) No idling current was showing on the meter and when the CW key was depressed the keying relay operated but no plate current was indicated. A quick check of the schematic showed that the problem was most likely in the operation of the CW relay, K-103. A quick check accessing the K-103 relay coil terminals for testing through the vent holes in the rear panel of the transmitter showed the coil was open.

An original replacement K-103 would involve quite a bit of time to locate. Since rewinding the coil of the relay wasn't really too difficult, I decided to proceed with a repair instead. First, to access K-103, the transmitter bottom had to be removed. Then the bottom-rear panel can be removed and the two relays, K-103 and K-104 are mounted on the inside of that panel. I tagged all of the wires soldered to the 10 terminals on K-103 to make reinstallation easier and then unsoldered them and dismounted the relay. The relay coil is held in place with a single screw. Once the coil is out of the relay, then all of the original magnet wire has to be removed. By the way, the "break" in the wire never seems to be at the beginning of the wind. I just cut all of the original wire out with an Exact-O knife and remove it with needle nose pliers (or my fingers.) I measured the thickness of the original wire so I would know what gauge magnet wire I would need. The original seemed to be 33 gauge but all I had on hand was 32 gauge.   >>>

 >>>  I used a motor driven coil winder I had built about 30 years ago. It's very basic in design and uses a "light dimmer" control as a motor speed control for the small sewing machine motor. This allows me to wind a solenoid-type coil pretty fast. I threaded an 8-32 stud into the tapped hole in the coil spool so I could install that stud into the chuck of the coil winder shaft - see photo below. You have to start the winding slowly and this is where a variable speed motor control is really necessary. Once the motor speed is about 100RPM, it is easy to just use your fingers for tension and to also guide the wire onto the spool. When it appears that the coil is about the proper dimension, I stop the motor and clean a spot on the wire so I can measure the DC resistance from the "inside" terminal to the clean spot - this would be the total DCR of the coil so far. I'm looking for around 125 ohms DCR and when that is achieved, the coil is finished. After the coil was wound, I wrapped it with black electrician's tape and then lacquered the exterior of the coil. The original coil had "125" stamped on the side, so I added that to this replica coil and then mounted it back in the relay. Operation was just like an original relay.

Resoldering the wires to the relay was easy since all of the wires were tagged and their proper location readily found. After all the wires were connected and soldered, I coated the solder joints with the yellow-tinted lacquer to simulate MFP coating. Below are photos showing four of the steps to completing the repair of K-103.

Testing the CW Mode - The ART-13A was put back into the operating position and connected back up to the station antenna system. My initial test was on 3974kc, our Vintage Military Radio Net frequency, but since it was mid-day there would be no activity. This test showed that the ART-13 did indeed function in the CW mode now. The next test will be an actual CW QSO on 40M.

photo above: Coil spool in the chuck - ready to wind.

photo above: The coil after winding.

photo above: The completed K-103 with new coil

photo above: A repaired K-103 installed on the back panel

Final Assessment - It's hard to believe that the ART-13A in the photo to the right is the same "parts set" shown at the beginning of this section. Though this ART-13A turned out really nice and works great, let's consider what was necessary to get the transmitter operational. First, I had to find an Audio module - $67 with shipping off of e-Bay (and I had to repair/restore it.) A set of three wire wound resistors - $45 from Fair Radio. Plate Meter - $35 with shipping, Fair Radio. The MCW/FCI module that was a spare had been purchased earlier for $30. The sheet metal piece was $21. The total for missing parts was $198. Luckily, I didn't have to buy any tubes. In addition to that, figure that I had to spend about two weeks putting the transmitter together and getting it operational. I still have to build an AC operated power supply specifically for this transmitter. Of course, I did essentially get this ART-13A as a "freebie" that was included as a "parts set" for the Navy T-47. So, I started with a "zero investment" but, as far as saving any money on this project - that didn't happen. Unless you really enjoy all the aspects of restoration - parts hunting, cosmetic restoration, mechanical reassembly, testing, troubleshooting and repairing, it's probably best to avoid these types of "basket case" projects. The positive side is, of course, "bragging rights" to having saved another ART-13 from the oblivion of the scrap heap.

photo right
: The ART-13A sn 417ACG after completion of the restoration. Note that the two meters don't match. This is commonly found on many ART-13 transmitters and is probably due to past depot repairs, however, in this case the Plate meter is a replacement acquired from Fair Radio Sales.

UPDATE - ART-13A "Basket Case" -  March 2013

photo above: This is the ART-13A "Basket Case" as it now looks in 2013 in our Vintage Military Radio station in Dayton, Nevada. This configuration with the BC-348-R receiver would be referred to as the ARC-8 but to be accurate that ARC-8 should be powered by dynamotors and this station actually is using AC power supplies for both receiver and transmitter. Note the auxiliary capacitor to the left of the ART-13. This air variable capacitor allow precise setting of the loading of the transmitter. Details on the construction of an auxiliary capacitor box is in the section below "Operating the ART-13 on the Ham Bands Today." Note that there is now a Calibration Book in the book pocket along with the correct type chain and sleeving for securing the book to the pocket. Also note that all of the panel screws have been changed to stainless screws along with using external star washers. Most ART-13A transmitters that I've worked on seem to have stainless (or at least silver finish) screws with external star washers rather than the "raven finish" (black) screws and internal star washer used on the earlier Collins' versions.
We're really never finished with projects like the "Basket Case" ART-13A. We're always keeping watch for parts needed to improve the transmitter's appearance or performance. This ART-13A needed a Calibration Book and I found an excellent example on eBay. Although it wasn't cheap ($70) it was in very nice condition. This required finding the right kind of chain to secure the book to the pocket and the right kind of sleeving to cover the chain.   >>>

>>>  A method of securing the book to the chain and the chain end to the pocket were also needed. The correct chain was found at a specialty hardware store and the sleeving was salvaged from an old piece of rotor cable. I made a "fake rivet" out of a brass screw and nut for the attachment to the book pocket and then painted the "fake rivet" flat black. The installation looks very original with the right amount of patina.  (See close up photo to the right.)

I was also able to remove some other items needed from a "parts set" ART-13 that belonged to KØDWC. The original Instruction Plate on the lower front panel was in poor condition but the "parts set" had one in nice shape. If you carefully drill the back of the rivets just enough to remove some of the rim they can be "punched out" with a small metal punch. This saves the rivets for reuse. The new Instruction Plate was mounted by installing the old rivets and then deforming the back of each rivet with a suitable punch. The front of the plate and the rivets have be held against a piece of hardwood to keep the rivets tight while punching. To fully secure the plate, use clamps to make sure the plate and rivets are tight against the panel and then apply a small drop of 5 minute epoxy to the back of the rivets. When that's cured, the plate will be secure and tight along with looking perfect.

I also replaced the mismatched meters with a set of matched Weston meters from the "parts set." Also, the original K-103 that I repaired was replaced with a good condition, functional K-103 unit from the "parts set." Also, the old "repaired" Interlock switch was replaced with a good condition, functional original.

I was given the OA-17 LF Oscillator as pre-payment for some work on a T-368 transmitter that is owned by KØDWC. The OA-17 just about completes this ART-13A "Basket Case" with the only other item needed being the shock mount.


T-47/ART-13  "Restoration of a Typical Example"

This example of the restoration process features a very complete, good condition ART-13. Only minor disassembly and only one missing part made this restoration straight-forward and is typical of most ART-13 restorations today.

Deceiving Appearance - The photo to the right shows the other ART-13 involved in the "Big Trade." Though it looks to be another "parts set" it's actually in pretty good shape. With this Collins-built USN T-47, all of the parts were present except for the MCW/FCI module. The obviously missing meters were carefully wrapped in bubble-wrap and in one of the parts boxes. Knobs, the lid, and other minor items that were not on the transmitter were in the boxes. The Audio Module was partially disassembled but this was minor and only involved replacing some screws and nuts. Tubes were carefully wrapped in one of the parts boxes. I found a MCW/FCI module off of eBay. These are usually pretty cheap with this one costing $15 plus shipping.

Reassembly and Body Work - This transmitter required the same sort of searching through the parts boxes but on a much smaller scale. All of the parts were easy to find since they were obvious items that were very recognizable. Note that the handle on the left side is bent. Actually, the sheet metal panel is bent. This required removing the handle and using a clamp and small wooden blocks to straighten. Even doing this carefully resulted in some of the paint chipping off. The area was painted with Krylon Black Wrinkle Finish using a small brush. Then the area was heated using a heat gun to activate the wrinkle. After the wrinkle had dried overnight, I matched the actual color of the panel with Artist's Acrylic paint.

Everything needed a good cleaning. I used Glass Plus for most of the cleaning. The wrinkle finish was cleaned using a soft brass brush and Glass Plus. Afterwards, Armor All was used to improve the looks of the original paint. The knobs were soaked in dish soap and water for about an hour and then cleaned with a tooth brush. Armor All can also be used on the knobs.

photo above: This USN T-47/ART-13 is actually a pretty good candidate for restoration. An added bonus is the Navy version of the OA-16 LFO is installed. It looks pretty bad in this photo but all of the parts were in boxes and the transmitter only needed to be reassembled.

Power Supply Construction and the Amazing Nemic-Lambda - I built a power supply entirely out of my junk boxes. It was a pretty standard for a tube rectifier design and used 866MV rectifiers for the +HV and a 5U4GB for the +LV. The unusual approach was to use a modern and very small Nemic-Lambda 10A power supply for the +28vdc. I saw this supply on eBay with a "Buy it Now" of $25. I couldn't resist the price so I purchased it. When it arrived I thought I had been sent the wrong item. It was about 3 lbs total weight. The size was 4"W x 4"T x 9"D. Nothing that small could provide +28vdc at 10A! A set-up and test proved to me that modern switching power supplies are amazing. I monitored the output with an oscilloscope and was amazed that the ripple voltage never changed from minimum load to maximum load. I left the Nemic-Lambda running the ART-13 +28vdc requirement for one hour with no problems and no over-heating. Also, older switching power supplies had a reputation for very noisy outputs with a lot of "switching noise" apparent on an oscilloscope when monitored. This Nemic-Lamba has no "switching noise" on the output whether at full load or no load. Simply amazing. The homebrew power supply is described in more detail in the "AC Power Supply" - "Hommage a le Valve" section of this web-article. Testing - Initial testing showed that this T-47/ART-13 worked with no issues. I was amazed that the transmitter had been partially disassembled and yet went together easily and worked on the first try. Initially, I used a fixed 400pf ceramic external capacitor to allow matching to my tuned dipole. I was able to get about 165 watts output with the transmitter but the audio sounded weak and under-modulated. I had selected the pair of 811 tubes for "matched" equal test results without too much regard for their maximum test readings. The T-47/ART-13 requires 811s that are at least measuring "minimum acceptable" to provide adequate modulation. Replacing these "weak" tubes with better (though not exactly matched) condition tubes resulted in great modulation characteristics.

photo above: The completed T-47/ART-13 sn 4628 built by Collins Radio Co. for the USN. Note the rubber mounts that are under each of the shock mount rails. These help to elevate the bottom of the transmitter to provide cooling. The shock mount rails are the early style that are separate from the bottom cover.

Final Assessment - This was the first T-47/ART-13 that I had worked on and restored to working condition. It was a fairly easy project that took about seven weeks to complete, including the design and building of the "Hommage a le Valve" AC power supply. The power supply was actually at least 80% of the time required to complete the project. This is normal in the restoration of your "first" ART-13 since from then on you have the means to easily power-up your next ART-13 projects.

At first, I had the Channel Selector switch set to MANUAL while I was learning how the transmitter operated. After a week, I started to setup some of the Autotune channels. I was generally operating on 3870kc or 3974kc and power output was about 160 watts.

For audio I used some military microphones at first but discovered they didn't fully modulate the ART-13 at the increased RF power. Although specific mikes are called for in the manual, these mikes seem to only provide sufficient modulation if the carrier power is reduced to around 100 watts. I found that using a DH-50 crystal mike (with a Kobitone element) on an Astatic TUG-8 stand (amplified) provided fully adjustable audio drive with more than enough audio output for full modulation at 150 watts output power.

This ART-13 project was fairly easy and no serious problems were encountered. For the most part, if a complete and good physical condition transmitter is purchased, this will give you the best chance of completing the project with very few, if any, problems.

UPDATE  -  Collins T-47/ART-13  -  March 2013 - The T-47/ART-13 is now located in the upstairs radio room in Dayton, Nevada. We have set up this ART-13 transmitter to run with the Solid-State Dyna-Sim AC Power Supply which "stacks" a +400vdc power supply and a +900vdc power supply to allow the +HV to run around +1300vdc. This "series" method is how the dynamotor achieves its +HV and the power supply can be built using easier to find parts. The plans for building this type of AC power are below in the "Homebrewing an AC Operated Power Supply for the ART-13."

To the right of the ART-13 is the RCA CGR-32-1 receiver built for the U.S. Coast Guard in 1940. These receivers were special built versions of  RCA's AR-60 receiver. The receiver is connected to the LS-112 on the wall (it's out of the shot.)

Above the Dyna-Sim power supply is another auxiliary variable capacitor. This air variable has not been painted - yet. I typically run the T-47 with the Shure Bros.102-C carbon microphone to provide the listeners with an authentic "military sound" to the signal.

UPDATE -  Sept 2017 -  This T-47/ART-13 is now set up with a DY-12 dynamotor powered by a PP-1104 power supply. Location is the shop.


T-47A/ART-13  (sn:2054 from 1944) - Restoration/Rebuild of the $10 ART-13

Those of us "collector-hams" (and especially "vintage military radio collector-hams") can't resist a bargain. When I was offered this rather "rough condition" ART-13A for a ten dollar bill, I wasn't looking for another project but sometimes the "collector" takes over and the combination of "bargain plus project" is too much to resist. This ART-13A presents some different challenges beginning with a thorough cleaning to assess what damage (if any) was caused by the wasp infestation that left many "mud dabber" nests throughout the internal parts of the transmitter. This project covers the basic steps necessary to get an original transmitter that was "storage challenged" up and running along with what cosmetic procedures are necessary to end up with a respectable appearance. - H.Rogers Oct. 12, 2015

photo above
: ART-13A sn:2054 from 1944 "as found." Dusty and dirty but essentially complete and original. The knob nomenclature is worn but the panel lettering is in good condition. The lock bar plates need repainting. The yellow tag laying on the lid is an acceptance tag indicating "ready to use." Note the cover from the tuning booklet is in the pocket.

October 12, 2015 - I picked up this ART-13A today in Sparks, Nevada. It was very reasonably priced (ten dollars) probably because of the condition of the interior of the transmitter. It had a lot of "mud dabber" (wasp) nests inside. I figured that, at the least, it would be a good "parts set." When I got it home I was then able to inspect it closely. Overall, sn: 2054 was very complete although very dirty. The only thing missing was the tuning book and at least the cover of the book was present in the pocket. All of the knobs were in un-chipped condition. The plastic cover over the tuning chart was gone but the paper chart is in pretty good condition. The yellow tag that was tied to the left grab handle was a "ready for use" tag that indicated that the transmitter had been tested and was found operational in 1954.

On the downside, the "keying" decal by the KEY input jack is badly deteriorated as is the decal on the lid.

I decided that if the ART-13A passed all of my initial pre-tests, it would probably be a good candidate for a rebuild.

Quick Check - Oct.16, 2015 - I tested the modulation transformer and found it to be the older style with 150 ohms DCR Screen winding. All windings tested fine. Also, both meters tested okay. K-103 and K-104 tested okay. All chokes tested okay. I also discovered that the MIC Switch was "safety wired" in the Carbon position. This is typical for an ART-13 straight from the military.

These tests assured me that the most important parts were okay and the transmitter would probably be fairly easy to get operational.

photo left: SN 2054 output section doesn't look too bad. Dust, dirt and a few wasp nests in the front left corner. These nests wrap around the TEST switch and somewhat surround the RCVR antenna input terminal.


photo right: SN 2054 showing the modulator module, frequency calibrator module, 1625 multiplier sections and the 813 output tube. Lots of wasp nests on this side of the transmitter. Note the one nest that surrounds the Second Multiplier tube (center top of photo.)

Update October 26, 2015 - It looks like ART-13 sn 2054 is going to require substantial disassembly in order to remove all of the wasp's nests. I checked the controls to see if they rotated freely and found that Antenna Loading E was immoveable and High Frequency Tuning Coarse A felt "locked" but it would "rock" somewhat. First though, I wanted to test my wasp nest removal process and see if it was going to work. I removed the FCI module and the Audio module to clean that area of the transmitter chassis. I found that Glass Plus spray and a small acid brush did a pretty good job at removing the wasp's nests. It was very messy but essentially the nest disintegrates and you're left with Glass Plus and wet dirt. Every so often there would be some insect debris mixed in with the mud. I had to be careful not to break any components or wires so my technique was to spray the nest carefully (to result in only the nest getting wet) and then brush the wet nest with the acid brush. This was repeated until the nest disintegrated and all that was left was residual Glass Plus and wet mud. This was removed with paper towel pieces, Q-tips and dry paint brushes. Tedious work but the results were worth the effort.

When I removed the ART-13 bottom cover I could see why the Antenna Loading condenser wouldn't move - it was full of wasp's nests. This took about an hour to clean with Glass Plus and brushes finally resulting in an easy to adjust E control. I could also see the Multiplier Section had several nests that were responsible for the "locked" Course A control (more on this in "Problem Two - Serious,"  below.) I decided at this point it would be necessary to remove all of the sheet metal cabinet pieces to have full chassis access for nest removal. The photos right and below show the permeably tuned coils for the Multipliers that are located just behind the PTO. The wasps built this nest right around the 1st Multiplier coil form (photo right.) It took about an hour to carefully remove the nests with Glass Plus and brushes followed by a clean up of the area with paper towels, Q-tips and dry brushes. Complete access allows for a thorough "clean-up" of the disintegrated nest material and resulted in the transmitter chassis looking really nice. See photo below left. 

photo above: The permeability tuned Multiplier section after cleaning. The only sections of the ART-13 that didn't have wasp nests were the PTO and the Autotune. Both of these sections are very well sealed and were inaccessible to the wasps. This Multiplier coil section always seemed to "collect" the debris from cleaning. I had to repeatedly clean this area several times as dirt and "mud" always seemed to collect here.

Update Oct 31, 2015

All of the wasp's nest were now removed (I thought.) I had to substantially disassemble the ART-13 as can be seen in the photo to the right. Only the PA output panel and the power input panels were not removed during nest removal. As can be seen in the photo, the wasp's nests didn't do any damage to any of the components or to the sheet metal and any minor residual nest material can be blown out of the chassis after it dries (since then it's just fine sandy dirt.) The next step was to further clean and lubricate the various contacts and switches that were affected by the wasp infestation.

Reassembly and Testing - Nov 7, 2015 - I moved the transmitter and parts from the shop to the upstairs repair and test area for reassembly and testing. Once upstairs with better lighting, I saw there was yet another wasp nest buried in the Multiplier section. This was removed in the same manner as the other nests. More detailed cleaning followed until the transmitter could be turned upside down and no dirt or "mud balls" fell out.

Body Work and Tube Testing - The reassembly did require some of the panels to be straightened. This was accomplished with oak wooden blocks as cushions and a weighted hammer. Though this sounds like rough treatment, the panels don't loose any paint and end up nice and straight. With all of the panels back in place, now it was time to test all of the tubes. The testing showed all tubes to be in excellent condition except one of the 6V6 tubes had an internal short. Next, was to apply some +28vdc and see how the Autotune worked.

Problem One - Minor - Autotune - Before +28vdc was applied, I manually checked the operation of the Autotune by turning the main shaft by hand. Then I lubricated all of the bearings with 10W oil and greased the worm gears with red wheel bearing grease. I also lightly lubed each of the moving parts in each of the tuning modules. 

With only +28vdc connected to the ART-13 and with Channel 1 selected, the power switch was thrown and the Autotune ran to zero (correct) and then proceeded to run all the way the other direction and then stopped (not correct.) Switching channels didn't result in the Autotune running to zero again. Usually most problems with the Autotune are in the forward limit switch or the rear limit switch. In this case, the contacts on the rear limit switch were very dirty and cleaning with DeOxit got the Autotune working correctly.

Problem Two - Serious - Nov 10, 2015 - We were now at a point where we could apply the +HV and +LV and see how the transmitter was going to work. This test resulted in no grid drive (well, at least we didn't blow any fuses.) The lack of grid drive was due to either the PTO or the first Multiplier not working. Further testing was required to determine the specific problem causing the lack of grid drive. A quick test showed that the PTO was operating. I measured the plate voltage and also used a pick up to see the PTO output on the oscilloscope. I did the same thing for the Multiplier tube and had both plate voltage and output signal but no grid drive to the 813.

With power off, I attached one lead of a DVM (in ohms) to the input side of the Multiplier's output coupling capacitor and the other DVM lead to the plate of the 1st Multiplier tube. I should have had continuity but it showed open. Upon close inspection I noticed that one of the arms of the 1st Multiplier section switch was twisted and bent up therefore not making contact with the switch contact buttons (see photo right.) I was very careful not to "force" any of the controls during inspection so I'm sure this damage happened in the past when someone "test-turning" the controls forced control A while a wasp nest surrounded the switch arm. Forcing the control to move must have bent the switch arm as it pulled loose from the wasp nest.

The first Multiplier switch is "buried deep" in the chassis and removing any components is next to impossible without removal of the PTO section of the transmitter - a difficult operation. I was pretty sure with a very long and thin needle nose pliers and a couple of long thin screw drivers, I could bend the arm back to its original position. This had to be carefully done since breaking any part of the switch would be a disaster. The operation took about 10 minutes and the switch function was back to normal. A continuity test showed everything was working fine.  >>>

photo above: The Multiplier switch within the Multiplier chassis showing the bent and twisted arm of the switch. Access is rather limited but with special tools the switch arm was bent back to its correct position while maintaining its "springy" positive contact with the switch buttons.
>>>  The "power on" test still didn't have any grid drive with the problem being the PTO this time.

With a rapid operation of control A back and forth a few times suddenly there was grid current.

Although I had cleaned the contacts several times with DeOxit, apparently actual friction of the arm contacting the buttons was necessary to break through the oxidation or contamination. This time the ART-13 loaded up into a dummy load with no problems and had full output.

Cosmetics - The knobs had most of the white paint fill for the nomenclature missing. The locking bars and their backing plates needed to be repainted. The black wrinkle finish needed to be reconditioned and touched-up. All of the cosmetic restoration was performed as described in the section titled "Refurbishing the Cosmetics" above in this article.

As to details,...I used black nitrocellulose lacquer for all touch-ups and for painting the locking bars and their backing plates. At first the paint looks way too dark because the original wrinkle hasn't been reconditioned. Let the lacquer dry for an hour and then rub the wrinkle finish panel with a cotton pad that is lightly saturated with clean 10W machine oil. Wipe the panel down with a clean cotton cloth afterwards. The black wrinkle finish will now match perfectly the black nitrocellulose lacquer. I've found that using Mars Black Artist's Acrylic as a touch up paint is problematic and sometimes the touch-up looks somewhat "brown" rather than black, especially if Armor-All is used to enhance the original wrinkle finish. I'm getting much better and more consistent matching using the black lacquer and reconditioning the wrinkle finish with 10W machine oil.

Reassembly - November 17, 2015 -  At this point, the ART-13 had been completely reassembled and was looking very nice. I did have to do some body work on the tuning book pocket since it was bent in several places. I used oak blocks and a weighted hammer followed by touch-up with black lacquer.

Further testing was necessary before the transmitter could be put "on the air." I wanted to make sure the Autotune was fully functional and that I set up the first several channels to frequencies that I use. I also needed to look at the waveform in AM on the oscilloscope to see that 100% modulation was possible. Finally, I needed to have the transmitter operating into a dummy load and then listen to the signal in a receiver that was not connected to an antenna. By listening to the receiver using a headset, I could get a very good idea of how the ART-13 would sound "on the air." Additionally, I needed to try the CW mode and verify that mode functioned correctly.

Chassis Cleaning - Since I had essentially removed nearly all of the sheet metal panels during the wasp's nest removal, I had the opportunity to thoroughly clean in many places that are normally not accessible. The end result was a chassis that looked very nice in addition to being fully functional. Here's some cleaning details,...

The final tank coil was pretty dirty between the windings. Fortunately, the coil spacing allows access with a "horse hair" tooth brush with Glass Plus. The dirt can be brushed out going in the same direction as the winds. All chokes were also cleaned with a horse hair brush and Glass Plus. The Glass Plus evaporates leaving no residue.

The area containing the 811s and the 813 tubes was MFP coated. There doesn't appear to be MFP anywhere else in the transmitter. Area cleaned with Glass Plus and various paint brushes.

Tube sockets were cleaned with DeOxit. Switches were also cleaned with DeOxit. The three Jones' plugs were cleaned with DeOxit.

Relay contacts for K-103 and K-104 were cleaned with 600 grit AluOx paper followed by DeOxit.

At this point the ART-13 was functioning using the Dyna-Sim AC power supply with the transmitter output connected to a 50Z ohm dummy load with air variable auxiliary condenser. However, the transmitter was still on the test bench.

photo above: SN 2054 after cleaning, reconditioning and reassembly.  

photo above: The test set-up for SN 2054. Note the Motorola roll-cart. I got this from Dave Walker, who retired from his "Walker Electronics" business in Reno in 2012. The roll-cart was given to Dave by Bill Lear.
Functional Test - November 19, 2015 - I didn't want to put SN 2054 "on the air" without first testing how the audio looked on the oscilloscope and how it sounded in a receiver. Shown to the left is a set-up for testing the ART-13. The Dyna-Sim power supply is on the floor but the cable can be seen routed behind the yellow tag at the left side of the ART-13. The mike used is a Shure 102-C carbon microphone. The metal box on top of the ART-13 is the auxiliary condenser. To the left of the transmitter is a Harrison 1KW 50 ohm dummy load. Further to the left is the monitoring receiver, a Collins R-388 (a 12" pick-up antenna is necessary since the receiver is well-shielded.) Note that the audio output from the receiver is to a 600Z ohm headset. This allows me to listen closely to the character of the audio from the ART-13 without feedback occurring.  Not visible in this shot is the equipment to the right of the transmitter which consists of a 561 Tektronix oscilloscope, a General Radio Digital Frequency Counter and other various types of test equipment.

With the ART-13 running at approximately 150 watts of carrier output into the dummy load, the waveform was observed on the oscilloscope. Close-talking the mike resulted in obvious "cut off" at 100% negative modulation. Best results were with the mike about 4" from the mouth. Next, the 'phones were put on and the signal tuned in on the R-388. Again, it was noted that "close-talking" the mike resulted in fairly noticeable distortion but with the mike about 4" away from the mouth, the audio sounded undistorted and clear. Of course, the test was using a carbon mike so the typical "carbon sound" was apparent. Inspection of the Audio Module revealed that it had the common modification of changing R203 from 15k to 4.7k. This increases the carbon mike bias for better response (certainly necessary for the typical T-17 mike but a little "hot" for a really responsive carbon mike like the Shure 102-C.)

The Penultimate Test - November 25, 2015 - While still connected to the dummy load, I verified that the ART-13 also sounded fine using a TUG-8 amplified base with the Audio Module switched to DYNAMIC. This position is used when the particular net being checked into isn't populated by military radio collectors. The ART-13 can produce excellent sounding AM when operated in this configuration.

The next step was to connect the ART-13 to the tuned dipole antenna and actually transmit a signal. In this operating position I have other monitoring equipment to check modulation levels and transmitting frequency. I set-up four channels on the Autotune for the "most used" frequencies on 75M. I then telephoned KØDWC, who is located about 3 miles away, to have him listen at his station to my transmitted signal. This provides the penultimate test before actually going "on the air." Chuck's report was "an excellent sounding AM signal - clean, clear audio."

The Final Test - Novemeber 28, 2015 - Of course, the final test is to actually use ART-13 SN: 2054 on the air during a regular AM net. My first net to try was the Saturday Morning AM net on 3870kc. This net is populated by regular AM ops so the reviews were from the perspective of "broadcast quality" audio. I used the TUG-8/DN-50 mike in the DYNAMIC position for hopefully the best quality audio response. Conditions were very good and all reports coming back were positive in both audio quality and signal strength. I was running SN: 2054 with the Dyna-Sim power supply so I was able to load the transmitter to about 150 watts of carrier power output. Antenna was a 135' tuned inverted-vee.

photo above: ART-13A SN: 2054 after the rework and cosmetic rejuvenation was finished. I left the original tuning chart in place since it was in good condition but I added a heavy plastic cover over the chart. I also have the yellow "ready to use" tag hanging from the right side handle. The calibration booklet is for an ART-13A but was installed in my T-47 where it was really too thick for the pocket (T-47s used a thinner book that was for the early FCI module.)
Final Thoughts - So, I didn't have to buy anything to get SN:2054 up and running. I did have to put in about 12 to 15 hours of work to get the transmitter into functioning condition and looking pretty nice. All in all, it was a relatively easy project that was completed fairly quickly and the end result is a great condition, functioning ART-13A. These types of "projects" workout well for the ART-13 enthusiast that already has access to all of the accessories that are needed for restoration, troubleshooting, testing and operation.

Update - September 12, 2016 - I've been using this ART-13A on a fairly regular basis, which would be about once a week. The only problem encountered has been an intermittent contact on one of the finger contacts in the Antenna Loading network (Course C.) The contact clears up with a slight rocking of Course C. This problem occurs rarely and then only when the channel is changed which actuates the Autotune. It's so minor I haven't tried cleaning the finger contacts but I probably will if it starts happening more often. I've set this ART-13A up running on the Dyna-Sim Solid-State power supply and it works with the 1948 National RCR Airway receiver.


Operating the T-47/ART-13 with the DY-12 Dynamotor

Upon setting up the "$10 ART-13A" as part of an operating station, I now had no way to operate the USN T-47/ART-13 transmitter. The thought of building another AC power supply didn't really sound like much fun but doing something different did. Why not operate this ART-13 on DC?

To set up an ART-13 for DC operation was going to require that I find an operational dynamotor. I found one locally from an old military-collector ham friend of mine. It was a DY-12 which was the correct type for the T-47/ART-13. Though not in the greatest cosmetic condition, it was fully operational and came with the correct DC input connector.

I still needed to find the DC output connector and another U7 connector. Additionally, a suitable cable had to be constructed for connecting the DY-12 to the T-47/ART-13. I bought the connectors off of eBay since this was the quickest way to get them here.

The manual doesn't specify the length of the interconnecting cable since each installation in an airplane was probably slightly different and depended on where the dynamotor was going to be located in relation to the transmitter. I decided that six feet was probably an average length. The cable used two 12 gauge wires, two 16 gauge wires and five 18 gauge wires. Pin 10 is the +HV and I used the center conductor and insulation from a length of RG-58 coax for that wire. The ART-13 manual cable breakdown only specifies the "minimum" wire gauge, so I used the largest gauge wires that would fit into the pin sockets. The wire bundle had to be shielded and wrapped with tape. The shield was made from the braided shield harvested from RG-8 coaxial cable. I connected the shield to the connector shell which provides a chassis connection at the ART-13 and also at the DY-12.  >>>

>>> Once the transmitter cable was complete, the DC input cable had to be built. The two wires were 8 gauge six feet long and once again the cable had to be shielded. The connector has a small pin that is connected internally to the DY-12 chassis. The shield has a drain wire that is soldered to this small pin on the DY-12 side connector. At the PP-1104-C side the other shield drain wire has a lug that is connected to the PP-1104 -28vdc terminal.

When operating the T-47/ART-13 with the DY-12, the +HV runs around +1100vdc. The resulting RF power output is 110 watts on 75M. There are two DC windings providing two outputs on the DY-12, +400vdc and +700vdc. Normally, the two DC outputs are connected in series for the +1100vdc HV. At high altitudes (>25,000ft.) a barometric switch changes the series connection to reduce the HV to only +700vdc (to prevent arcing.)

To attain full transmitter RF output, the dynamotor must run at its design speed which is achieved at a minimum of  +27.5vdc input. This is the voltage at the DY-12 input, not the voltage output of the power supply. There will be a voltage drop across the cable under load. The easiest method of determining the input voltage is to switch to BATT on the meter switch and adjust the power supply so that the BATT indication is at the top the mark on the meter. Alternately, a suitable point can be found inside the ART-13 and the input voltage measured. The lid will have to be off but since the T-47 doesn't have the interlock it's not too difficult to operate the transmitter filaments and see what the voltage drop is and adjust the power supply accordingly. In my installation, the standby voltage is +28vdc and loaded voltage is +27.5vdc.

The typical receiver that was used with a DC operated ART-13A was the BC-348 (also operated on DC) to comprise an ARC-8 set-up. This set up would require about 6 amps for BC-348 dynamotor start-up and about 3 amps when in operation. The BC-348-Q would have its own power cable that would also attach to the PP-1104-C. However, in a post-WWII (1947) "Radio News" magazine, I had found a photo of a ham station located in Hawaii that was running an ART-13 transmitter on a dynamotor and the receiver used was a USN RAO-7. The RAO-7 is an excellent performer and has ample selectivity. I have my RAO-7 set-up with a panoramic adapter which was standard for the receiver since they were primarily used for surveillance. Though not a typical WWII military set-up (like the ARC-8 would be) this pairing of the USN T-47/ART-13 and the USN RAO-7 seemed appropriate and was probably easy to do in the post-WWII, abundant surplus availability era.

Shown in the photo to the right is the T-47/ART-13 set up with the DY-12 dynamotor on the lower shelf under the table and the PP-1104 to the far right under the table. The cable from the DY-12 to the PP-1104 is six feet long and the cable from the DY-12 to the ART-13 is also six feet long. The RAO-7 is centrally located on the table with the T-47/ART-13 to the left and the USN-General Radio LR-1 Frequency Meter to the right. The panoramic adapter is the BC-1031-C located on the shelf above the ART-13.  This station is located in the shop.

The T-47/ART-13 running on the DY-12 dynamotor has a typical RF output on 75 meters of 110 watts to the antenna. The antenna is two half-waves in-phase (on 75M) and uses two 135ft wires that are center-fed with 77ft of open feed line, matched with a Nye-Viking coupler. I use a fixed 280pf 10kv ceramic capacitor for the external auxiliary condenser on the ART-13. To also add a bit of period flavor to the station, I operate the ART-13 using a Shure 102-C handheld carbon microphone. Between the dynamotor whine, the PP-1104 cooling fan and the carbon mike, the signal reports (and comments) are always interesting (even on vintage military radio nets.)     September 2017


Using the ART-13 on the Ham Bands Today

Microphones - The ART-13 Audio Module has a "fixed-level" gain setting that was designed to work with specific WWII vintage military microphones with the ART-13 operating at its standard voltage levels available from the dynamotor. There are a couple of carbon microphones specified and a couple of dynamic microphones also specified in the ART-13 manuals. The Shure Bros. Co. T-17 was probably the most commonly used carbon microphone by the military. Many ART-13s will be found with the CARBON/DYNAMIC switch "safety wired" to the CARBON position.

Carbon Microphones - There are two problems that are normally encountered with carbon microphones. First, the military expected the radio operator to "scream" into the microphone. After all, he was trying to talk over the aircraft noise and was probably being shot at! Second is that many vintage carbon microphones don't have the response they used to. Most military WWII carbon microphones will not allow enough audio for proper modulation due to "carbon packing," "carbon fusing" or other age and use related factors.

Though the ART-13 manuals will specify a couple of microphones to use with the transmitter, nearly always (if you happen to have the particular types) you'll find they don't provide enough response to fully modulate the carrier. For Carbon mikes you'll have to test several examples to find an element that still has proper response and has not been ruined with excessive bias voltage (which causes the carbon particles to fuse together.)

You can buy replacement carbon elements but many times these are of old manufacture that just haven't been used (NOS) but they don't seem to work any better than the well-used older elements. This is probably due to "carbon packing" - another common problem. It's also possible to buy new carbon mikes that do seem to work very well because they haven't been subjected to any abuse and also the carbon particles haven't had time to pack together. Typically, you'll end up testing a lot of carbon mikes before you find an acceptable example.

IMPORTANT - if you're having Carbon Mike problems - Check the value of R203 in the Audio Module of your ART-13. The original value of this resistor was 15K, which resulted in a carbon mike bias that was adequate for the typical T-17 when it was new. It wasn't long before the value of R203 was changed to 4.7K to give a higher voltage to the mike bias and therefore better response and gain. In the ART-13B schematics, the resistor value for R203 is shown as 4.7K. In all of the earlier versions of the ART-13, the value is 15K. Some carbon mikes will work fine with R203 at 15K but most won't. If your ART-13's R203 is 15K and you're fighting low response on every carbon mike you try, change R203 to 4.7K. I've found this upgrade on about half of the Audio Modules I've inspected, so it was  probably incorporated into many ART-13s as they went through the military repair facilities.

Dynamic Microphones - Many Dynamic mikes usually don't seem to fully modulate either but many times this is due to a mismatch of the impedances. Many of the vintage ham dynamic mikes were fairly Hi-Z, around 10K was common. This mismatch will result in low gain. You can use a matching transformer but that's really getting to be a hassle. Try to find a Dynamic mike that has an output impedance of 250Z ohms which is what the ART-13 is designed for. You might find that some of the newer 500Z ohm dynamic elements are also a good input Z match. 

An Easy Microphone Solution - The easiest method to have high output from the microphone, that allows you to run the ART-13 at a higher power output with 100% modulation, is to use a preamplifier between the mike output and the transmitter input. The Astatic TUG-8 mike stand is the easiest way to provide a preamplifier since a battery operated one is in the base of the stand. You can use any of the Astatic mike heads, e.g., 10-D, D-104, T-3, etc., and with the TUG-8 stand, these mikes will all sound fine and provide plenty of output. The preamplifier output Z is a fairly close match to the Dynamic input Z. Be sure to have the switch in DYNAMIC when using the TUG-8. Also, watch your transmitter's output waveform on an oscilloscope to set the TUG-8 "gain" control to proper level of modulation. The "gain" control is adjusted by a slotted shaft potentiometer that is accessed via a hole in the bottom cover of the TUG-8's base.

Operating AM (VOICE) - Initially, an oscilloscope must be used to determine if the microphone chosen is really a suitable one for the ART-13. The oscilloscope will almost instantly show you whether or not you are achieving 100% modulation. The easiest way to use the oscilloscope as a "modulation monitor" is to connect a "pick-up wire" to one of the vertical amplifier inputs. The length of the "pick-up wire" will be depend on your power output, location of the antenna and how much vertical amplification you use on the 'scope. Most of the time a three foot wire works fine, sometimes you might have to use a 10' wire - experiment with what gives the best 'scope pattern. While transmitting in VOICE, adjust the 'scope for a modulation envelope pattern and you will almost instantly see if you have full modulation. Just a slight "touch" at negative 100% is seen as either a slightly brighter "dot" at zero or a short "line" at zero. Both are indications that the ART-13 is modulating to 100% negative and you don't want to go any further than that with your audio drive level. Note the positive excursion also. This should be symmetrical and at 100% positive. If you find that you are not achieving 100% positive but are at 100% negative modulation you might have weak 811 modulator tubes. Also, it's possible that there is some excessive current being drawn on the +HV which limits the positive peaks of modulation. You can reduce carrier power somewhat and see if that helps with the modulation symmetry. Operating CW - Many ART-13 owners don't operate the transmitter in the CW mode. This really isn't because of a lack of CW experience but mainly because there are some limitations to "comfortable" operation in the CW mode. The ART-13, like most military transmitters, uses a Keying Relay to provide many functions inside and outside the transmitter. Outside the transmitter would be the Antenna switching and Standby function between the ART-13 and the receiver that provides "break-in" operation in CW. However, the Keying Relay is noisy - no doubt, on the airplane it was probably barely noticeable, but the typical ham shack will be a cacophony of racket when the ART-13 is transmitting CW. Also, if you're a fast CW operator, the Keying Relay will limit your speed. Although the ART-13 manual says that 30 wpm operation is possible, 15 wpm is a more realistic "speed limit." There are some modifications to eliminate the Keying Relay operation in CW and key the various circuits directly but one would have to decide whether or not the CW mode on an ART-13 was going to be a major facet of operation that would justify "hacking up" the transmitter. Besides, operating the ART-13 in CW in the original configuration is authentic and provides the user with some of the experiences that the airborne radio ops had to endure.
Antennae, Auxiliary Condenser and SWR - The ART-13 is not a ham transmitter, so it's not surprising that it doesn't readily operate into a dipole or quarter-wave vertical antenna. One of the idiosyncrasies of the ART-13 is that it was designed to operate into antennas found on aircraft. This was usually either a 20-60 foot end fed wire from the front of the plane to the tail, or a 200 foot long trailing wire antenna that was also end fed. Sometimes short whips were also used. Anyway, it's likely that no ART-13 ever originally operated into the 50 to 75 Z ohm unbalanced, low reactance (mostly resistive) type load that most ham antennas provide. The common solution is to add approximately 200pf to 800pf of capacitance from the COND terminal to the GND terminal which then provides a Pi-Network of sorts in Tuning positions 1 to 6. In positions 7 to 13, a Pi-network is already provided and usually above 7.2mc an auxiliary condenser shouldn't be required. Most amateurs operate the ART-13 in the 80-75M and this will require additional capacitance.

If you operate on just one frequency in the 80-75M band, then a fixed value capacitor can be used. It's also possible to provide several fixed value capacitors to provide optimum loading on several frequencies. It's also possible to use a transmitting air variable capacitor which will allow optimum setting of the antenna loading and any frequency or any tuning range. Most transmitting variables are about 350pf maximum capacitance and will require a capacitive shunt to increase the maximum value to around 800pf depending on exactly where you want the antenna loading to be set. Most users find that around 500pf works quite well on 80M. It will depend on exactly where you want to load up the ART-13 considering the power supply's current availability provided for the +HV and the ART-13 power output desired. (See section below "Air Variable Auxiliary Capacitor" for a description and photos of a method of mounting an suitable variable capacitor for this purpose.)

SWR - Be sure when loading the ART-13 into an antenna that you use the lowest setting of C that allows tuning the transmitter to the antenna load. Although you can find higher settings of C that might appear to tune to the antenna, you might actually be tuning the transmitter to a harmonic instead. If you have an SWR bridge in the antenna line, look at the SWR and, if the antenna is matched for say 80M and you show a low SWR, then the setting of C is okay. 40M operation is very prone to tuning to a harmonic - watch your SWR and monitor your transmitting frequency.

Frequency Monitoring and Why Zero Beating Doesn't Work - The easiest way to monitor the frequency of the ART-13 is with a digital frequency counter. The Counter can have a short "pick-up" wire connected to the counter input and that should provide sufficient signal for it to operate on. Normal AM net operations are on specific frequencies so it's rather easy to set the ART-13 up before hand.

If you have to do a minor adjustment to the frequency merely unlock the locking bar on Control B and fine tune the transmitter to the correct frequency. Be sure to re-tighten the locking bar afterwards. If you have the transmitter in MANUAL you can just adjust B to the correct frequency (leaving the locking bar tight.)

If you try to use the CALIBRATE position to zero beat the ART-13 tuned frequency to a received signal, you'll find that it doesn't work. The reason is the CALIBRATE position was to allow the radio op to use the FCI module's 50kc calibrate signal and to listen on earphones in SIDETONE for a heterodyne on the nearest 50kc cal point to the desired frequency for transmit. Only the PTO is in operation and it tunes 1000kc to 1510kc (in two ranges.) CALIBRATE was never intended for zero beating a signal in the receiver.

BC-348 Receiver Operating with ART-13  - ARC-8 was the designation for one of the most common set-ups for aircraft use of the ART-13 and combined it with the popular BC-348 receiver. Today, many hams run the ARC-8 configuration as it provides an aura of authenticity to a vintage military radio station (and the BC-348 is a great performing receiver.) The BC-348 can be wired into the U-8/U socket on the ART-13 to provide full break-in operation. Use pins 23 and 24 on the ART-13 U-8/U socket to provide a NC connection to pins 3 and 4 on the PL-103 connector on the BC-348 which will allow the ART-13 to control the stand-by function. Pins 23, 24 and 25 on the U-8/U socket access the internal sending relay in the ART-13. Pin 23 is Common (arm,) pin 24 is NC and pin 25 is NO.

Using the R-390A with the ART-13 - The R-390 and R-390A receivers require a NO set of contacts for receive and going to NC during transmit for proper BREAK IN operation of the receivers. You can use pin 23 (arm) and pin 25 (NO) to provide a proper "Break-in" for the R-390 or R-390A receivers.

Physical Location and Shock Mounts - There are a couple of different shock mounts that were used with the ART-13 transmitters. All of them are beyond difficult to locate. Probably when the transmitters were removed from service, the shock mount was left behind and scrapped with the airplane. Today, ART-13 transmitters are rarely offered or found with an original shock mount.

When placing the transmitter in its location in the station you will have to simulate what the shock mount provided. Not the vibration dampening but the elevation of the transmitter up off of its bottom plate. This elevation was how the ART-13 cools itself - by convection. Use spacers made of wood or rubber to raise the transmitter up so there is at least one inch of clearance between the table and the bottom cover. Two inches is better. This is usually enough to allow air flow and cooling.

Construction of a Variable Auxiliary Capacitor Set-up - By far the best method of providing the additional capacitance required for dipole antenna operation below 7.0MC is to use an air variable. The variable capacitor allows very careful adjustment of the loading and resulting power output of the ART-13 when it is used with an antenna that has low reactance. For months, I just had the variable capacitor setting next to the ART-13 with some wires connecting it to the COND and GND terminals. No problems were encountered with this method but it certainly looked non-military and somewhat dangerous. An aluminum housing was drawn up and we had the local sheet metal shop built four metal enclosures. These would house the air variable capacitors for my two ART-13 transmitters and two of KØDWC's ART-13s. The air variables were fairly large types that I had in the junk box with each having a maximum capacitance of 1000pf and a minimum value of 100pf. About mid-range works very well with the ART-13 when operating on 75M.  >>>

>>> Make sure that the capacitor rotor is connected to both the housing and to the GND terminal on the ART-13. Since the rotor is connected to the capacitor's frame, mounting of the capacitor to the housing accomplishes the ground connection. I used an SO-239 UHF connector mounted on the rear of the housing that also connects to the capacitor frame and the capacitor stator connects to the SO-239 center terminal. A piece of RG-58/U coax with a PL-259 on one end and the other end having the shield connected to the ART-13 GND terminal and the center conductor connected to the ART-13 COND terminal is how the auxiliary capacitor is connected to the ART-13. The bottom cover is a flat piece of aluminum that the sheet metal shop cut for me. The bottom covers mount to 1/4" aluminum square bar that is mounted in the housing. Tapped holes allow mounting the bottom covers and small rubber feet are attached to the bottom plate. I painted one of my boxes black wrinkle finish and then used a spare ART-13 knob (D control knob is 0 to 100, 180 scale.) The finished Auxiliary Capacitor box looks very military and like something that should go with the ART-13 transmitter.

Here are some photos of two ART-13 Auxiliary Capacitor Boxes. The air variable is 100pf to 1000pf. Connection is via a SO-239 connector using a short piece of RG-58U coax with a PL-259 connector running to the ART-13 COND and GND terminals.
Loading up the ART-13 on 75 Meters - If you read the loading instructions in the ART-13 manuals you are sure to be confused since these are written for operation with aircraft antennae. Hams generally are using a dipole antenna which will tune differently. First, make sure you have an auxiliary capacitor connected to the COND terminal to the GROUND terminal. This can be a fixed ceramic HV cap of around 500pf or a transmitting air variable that provides adjustable capacitance from 30pf up to 800pf. Depending on your air variable, you may have to use shunt capacitors to get up to 800pf.

1. Adjust Control E to 200 - minimum capacitance
2. Adjust Control D to mid-scale - around 50
3. Adjust Control C to triangle #5 (be sure the control is exactly set on the triangle)
4. Set switch to TUNE
5. Set A Control to triangle #4 and B Control to 8 on the small dial and 25 on the large dial (4.825 is approx. 3975kc)
6. Make sure your antenna is tuned to around 3975kc
7. Actuate the TEST switch
8. Use Control D to adjust Plate Current to minimum
9. Set switch to OPERATE
10. Actuate the TEST switch and see what the Plate Current is (this is total Plate Current so it is reading the 813 current plus the two 811 modulator idling current at this point.)
11. Adjust the Variable Auxiliary capacitor for the desired Plate Current (Loading)
12. Dip the Plate Current with Control D

These are the steps to load the ART-13 up to a tuned dipole antenna using a variable air capacitor as the Auxiliary Capacitor. When using a fixed capacitor, you won't be able to vary the loading as much. Use Control E to see how much variability in loading you have. You can only increase capacitance with Control E if it was set for 200. This will increase the plate current in the configuration used on 80M. Normally, the value of the "fixed" Auxiliary capacitor is chosen to give some adjustability on Control E for the desired loading for the frequency and antenna used.

NOTE: The ART-13 loading will vary somewhat depending on the level of +HV used. This description applies for +HV levels around +1400vdc. Higher or lower levels of +HV will result in slightly different resonant points for Control D.

40 Meter Operation - Operation on 40M is basically the same as 75M except that Control C will be advanced up to triangle #8 or higher. At this point, the output network is actually a  Pi-network and although the auxiliary capacitor probably isn't required, it does make loading much easier if it is used. Interestingly, the 40M band seems to be split with Control A referencing 7.2MC as the point of change. Usually, when operating in triangle #8 on Control A the lowest frequency tuned is about 7.15MC so you won't be able to tune into the CW portion of the band. Switch to triangle #7 on Control A for operation in the CW portion of the 40M band and you'll find that entire 40M band can be tuned. You might find that the Grid Drive Current is down a bit on 40M, since the alignment procedure allows for reduced Grid Drive at the band edges. 

Dealing with the Stacked Trimmer Capacitors in the Multiplier Section - If you plan to do an alignment of the Multiplier stages to bring the Grid Drive up then be very careful of the stacked adjustment capacitors - they are very delicate and easy to break unless the adjustment tabs are checked to see that they can be moved without difficulty. When the ART-13 was initially aligned, a "locking fluid glue" was put on these condensers so the adjustment would hold under the conditions usually found on airplanes in flight. The "breakage" usually occurs when the adjustment tab is "forced" to move against the locking fluid glue.

The first thing to try is using a heat gun to melt the locking fluid glue. Use the heat sparingly and try moving the adjustment while the trimmer is warm. The arm should easily break loose but be gentle and don't force anything.

If heat doesn't work then disassembly is the other option. The mounting screws can't be removed unless the VFO section is dismounted from the transmitter chassis. This is a very difficult procedure and not really necessary. The trimmer condenser mounting screws can be loosened and the nuts removed. This will allow the "stack" to be somewhat separated. This allows some access for lacquer thinner to be brushed on to remove the glue. Test as you clean for easy adjustment of the arm. >>>

photo above:
The  delicate "Stacked Capacitors" for aligning the Multiplier Section of the ART-13. These caps have +LV on them, so be careful and use an insulated alignment tool.
 >>> When the stack is reassembled, the adjustments can then be made without breaking the condensers. When doing the alignment, be aware that there is +LV (about +400vdc) on these caps so be careful and use an insulated alignment tool.

You can actually operate the ART-13 with the Grid Drive a little below the scaled area on the meter but if you have very low Grid Drive, you'll have to align the transmitter's Multiplier Section. Most of the Multiplier Section alignment issues are on higher frequencies - generally 7.0mc and higher. Usually there is always sufficient grid drive on 75 meters.

20 Meter Operation - 20 Meter operation is similar to 40M operation. You'll find that it is very near the top frequency that the ART-13 is capable of but usually no problems will be encountered. You'll probably have to have Control C at triangle #12 for loading up to full power. It's normal for the power output to be down slightly on 20M. I can get about 100 watts output on 20M with +1400vdc +HV.

Again, if you encounter very low Grid Drive you'll probably have to align the Multiplier Section of the transmitter. Use the procedure in the manual and be patient because it is a tedious, time-consuming job.

If you experience arcing inside the transmitter on 40M or 20M but not on 80M, it's probably a loading problem. Reset the position of control C first. If that doesn't help, try reducing the loading for lower total plate current. Most arcing problems are due to mismatched antenna loads.

30 Meter CW Operation - Since the ART-13 is continuous coverage from 2.0MC up to 18.0MC, it's possible to do some CW operating on the 30M band. This is a small segment from 10.100MC up to 10.150MC available for ham operation in CW/Digital modes only. Naturally, a general coverage receiver will have to be used in conjunction with the ART-13. Since most hams are using tuned dipoles for an antenna, be aware that these normally will work fine on harmonically related frequencies but may not allow loading on 30M. I just use a separate small dipole specifically cut for 30M. Dimensions are 23 feet per leg and I feed the antenna with coax and a 1:1 balun. Be sure to check the "30M Band Plan" PDF file because each segment of the 30M band is allotted to specific functions and modes. Also, 200 watts is the maximum power.

Operating the ART-13 on LF - 630 Meters (472kc to 479kc)

630 Meter Basic Info - This new Medium Frequency band is 472kc up to 479kc,...only 7kc wide. There's a band plan that allocates CW to the lower few kcs although CW is legal for the entire 7kc. Data transmissions are supposed to be in the top few kc. Operation is limited to 5 watts EIRP but since most antennae are so inefficient at 472kc, it could take perhaps 100 watts antenna input power or more to achieve the 5 watts EIRP. You will have to do some antenna modeling (calculations) to see the efficiency of your proposed antenna at 472kc and calculate what input power results in 5 watts EIRP. Additionally, you must submit your physical location to the Utilities Technology Commission for approval of operation on 630M. They will confirm that you are located more than 1km from the nearest power transmission line that might use controlled-carrier troubleshooting data on it.

Equipment Required - Your ART-13 must have the plug-in LF Oscillator module installed. There are two types, the early "Navy" version with six ranges (O-16/ART-13  - 200kc up to 1500kc) and the later "USAAF" version with three ranges (O-17/ART-13A  -  200kc up to 600kc.) Both types tune 630 meters (472-479kc.)

Once you have the LFO module, then you'll notice (when looking at the ART-13 schematic) that there's no RF output antenna coupling stage for LF inside the ART-13. The LF output from the PA is coupled through the plate blocking capacitor directly to the terminal marked "LOADING COIL" (J-117.) Onboard the airplane, an "ANTENNA LOADING COIL" (antenna tuner) was installed if LF operation was going to be required. CU-32/ART-13A Antenna Loading Coil was the largest version with the most elaborate circuits and it was built specifically for the USAAF. It allowed tuning the normal type of aircraft antennae for operation with the ART-13 operating from 200kc up to 600kc and included a RF amp meter. There was also the smaller USN CU-25 that used a much simpler circuit but still allowed tuning from 200kc up to 600kc. There was also the small USN CU-26 that was used for tuning 500kc up to 1500kc. The CU-32 allowed switching from either a trailing wire or a fixed antenna. The CU-25 and CU-26 were for trailing wire only. The CU-32 is shown in the photo to the right on top of the ART-13. It should be noted that the CU-32 is about the same size as the ART-13. However, it does weigh considerably less than the ART-13 (note the photo below to see why the CU-32 is a "light weight.")

photo above: ART-13A with O-17/ART-13A LFO installed with CU-32 Antenna Loading Coil on top.

LF Tuner Details - Of course, the upshot is that you can't operate the ART-13 on 630M without some type of antenna tuner. It doesn't necessarily have to be the CU-32 or the CU-25. A homebrew tuner could provide the impedance matching. If you're considering using the CU-32 or CU-25 Antenna Loading Coils, remember that these tuners were specifically designed to work with the antennae that are found on WWII aircraft. That would be the Trailing Wire Antenna, a variable length (up to 200') trailing wire that was reeled out the tail of the airplane while in flight. The Trailing Wire Antenna is essentially an end fed wire using the aircraft frame and fuselage as a counterpoise. The "Fixed Antenna" was generally a very short antenna that ran from the cockpit to the tail of the airplane and was "off-center" fed. These tended to load like a short vertical antenna. Fixed Antenna could also have been a short whip of some type (only the CU-32 matches the "fixed antenna.")  >>>
>>>  Whether the CU-32 can match a typical ham vertical is unknown. Only experimentation would provide the answer. The Trailing Wire output will work with an end-fed wire that is at least 100 feet in length worked against ground. Longer wires are somewhat easier to match. The majority of circuitry in the elaborate CU-32 is switching to allow both LF tuning and routing HF from the ART-13 through the tuner to the selected antenna in use. The CU-32 allows all connections between the ART-13, BC-348 and the CU-32 to remain attached and controlled by the ART-13 PTT line and selection of LF operation. The actual CU-32 "tuner" circuit is a simple LC network with fixed-C values and a variable L (variometer with loading coils.)

How the CU-32/ART-13A Antenna Loading Coil Works - When in LF, the ART-13 PA output is at LOADING COIL terminal. On the input side of the CU-32 is the "LF" terminal which is connected by a wire or cable to LOADING COIL terminal on the ART-13. CU-32 "HF" is connected to the ART-13 HF RF output using a wire or cable. When the ART-13 is not in "LF" the CU-32 is bypassed by having the vacuum switch and relay actuation voltage removed so the CU-32 always stays in "HF" if the ART-13 PTT line is actuated. When not in "LF," the ART-13 HF RF passes thru to the selected antenna connections on the side of the CU-32. TRAILING or FIXED can be selected and this selection ability is always active and applies to either LF or HF.

When "LF" is selected on the ART-13, then the RF output from ART-13 LOADING COIL terminal to CU-32 LF input is routed into the tuner circuit (via K-105 in the ART-13.) The CU-32 RF Amp meter is on the input side with series dropping resistors to chassis. Two parallel fixed-capacitors are from "LF" input to chassis. The "LF" input also connects to the loading coil/variometer. Taps are selected via the FINE LOADING. The variometer is used for PA PLATE TUNING. COARSE LOADING selects taps from the bank-wound coil under the Antenna switch. LF RF output is connected to the NO contact of the vacuum switch. "HF" input is connected to the NC contact of the vacuum switch. The arm of the vacuum switch is connected to the antenna switch that selects TRAILING or FIXED antennae. Actuation of the ART-13 PTT (key down) operates the ART-13 and the CU-32 vacuum switch which places the LF RF onto the particular antenna selected. The receiver is placed in standby via the ART-13 keying relay and the receiver antenna input is isolated by the CU-32 vacuum switch and by the vacuum T-R switch in the ART-13.

photo above
: Inside the CU-32 ANTENNA LOADING COIL showing the various components. The ART-13 inputs are to the right while the antenna connections are to the left. The vacuum switch and relay actuator is center-rear on the chassis (K-2501.) The relay is inside the metal housing. The fiber rod protruding out the top actuates the vacuum switch. This vacuum switch and actuation relay follows the keying of the ART-13 in CW giving the operator full break-in operation. The vacuum switch and relay operates on the PTT line and switches the CU-32 from "LF Input on transmit" to "HF Input on receive." Note the two spark gaps that are painted red. These are on the Fixed Antenna section to protect against arcing that is common with "short" antennae. Voice can't be used on LF with a Fixed antenna.

BC-348 Operation on LF with the CU-32 Loading Coil Tuner - The BC-348 was always connected to the ART-13's RECEIVER (J110) terminal. With LF selected on the ART-13, the vacuum switch inside the CU-32 toggles back to "HF" when the PTT line is deactivated (key up) and that then allows the BC-348 to connect to the aircraft antenna via the ART-13's "HF" routing through the CU-32. When PTT is actuated (key down,) the CU-32 vacuum switch toggles to LF which connects the ART-13 J-117 terminal to the CU-32 LF input. The ART-13 output is routed through the CU-32 to the selected aircraft antenna. The BC-348 is further isolated during "key down" via the ART-13's vacuum T-R switch. With PTT deactivated (key up,) the ART-13 and CU-32 return to "HF - Receive" mode. Since the BC-348 isn't routed thru the CU-32, the receiver's match to the particular aircraft antenna used would be dependent on its LF alignment on the Q, N and J versions. The other BC-348 versions have a front panel antenna trimmer for antenna matching although its effectiveness might be limited somewhat on LF.  The BC-348 does tune 630 meters and it can provide decent performance if aligned correctly on its 200kc to 500kc band. Of course, your LF receiver doesn't have to be a BC-348. Any LF receiver can be connected to the ART-13 RECEIVER terminal and utilize the ART-13 remote standby function (U-8/U connector) for fully integrated operation on LF with the ART-13. Or, you can use an entirely separate receive antenna such as a tuned loop. On 472kc, the use of a tuned loop receive antenna will greatly reduce the noise level and boost received signals. Directivity of the loop is also an advantage.

Operation of the ART-13 with the CU-32 on 630 Meters -  Operation must be on CW. This mode of operation utilizes a keying relay in the ART-13 that essentially is "keying" the PTT line. The keying of the ART-13 also provides keying to the vacuum switch in the CU-32 via the U-11/U connector/cable on the ART-13 (U-11/U is only operational if LF is selected on the ART-13.) Since there are three relays involved, the ART-13 keying relay, the ART-13 vacuum T-R switch and the CU-32 relay/vacuum switch, all working with the radio operator's keying, the maximum CW speed will probably be limited to around 15 WPM. I tried a bug and even at slow speeds (for a bug,) it's too fast for the relays to follow and allow the ART-13 to key "dits" properly. A hand key must be used and top speed seems to be around 15WPM.

Be sure to do your initial testing on LF with the ART-13 in the "TUNE" mode. This limits the power output to prevent excessive current flow when the PA is out of resonance. With a short end-fed wire of about 100 feet in length, you'll probably find that the two LOADING controls will be at maximum and the "plate dip" is fairly sharp. A 200 feet long wire will perform much better and will load up easier.

The actual CW signal on 473.5kc from my ART-13/CU-32 combo running into a 163ft end-fed wire sounded loud, crisp and clean as received by KØDWC located a few miles away. I've also had a two-way CW contact with K6KBE from Ione, California (located just over 100 miles away.) I've heard WØYSE on 630M from Washington state but haven't worked him,...yet.

Operating CW on the ART-13 with CU-32 is a very noisy experience. There are three relays "clacking along" with your sending. While the airplane was aloft there was so much other noise going on the sending relays were seldom heard, especially since the radio op normally was using 'phones. Not much can be done about the noise if you want to run the ART-13 and CU-32 as they were originally operated. Modifications to change any of the method of operation seems to go against the entire idea of collecting, restoring and operating WWII vintage military radio gear in the first place. Sure, it's noisy, but if you use a set of 'phones, as the old WWII ops did, it's not too bad.

For Sidetone to monitor your sending, the ART-13 provides two jacks to access the sidetone circuit. There is a volume control that is located under the tuning chart. Use a 600Z ohm load, either phones or loudspeaker. You can also listen to the receiver if you're using a separate antenna. Since I'm using a remotely tuned loop on the receiver, I just turn the RF gain down and use the SP-600VLF receiver as the CW monitor. Actually, with this method, I'm actually listening to the transmitted signal which is probably better since any problems would become quickly apparent.

Utilizing "Fixed Ant" and "Trailing Ant" for HF and LF Antenna Selection - The original intent of this switch was to select between a trailing wire antenna or a short vertical antenna, with both antennae being utilized for HF or LF operation. A more useable purpose for this switch is to use the "Fixed" position for the HF antenna. Then the "Trailing Ant" can be used for the LF antenna. When the ART-13 is NOT in LF, the CU-32 is bypassed except for the Antenna Selector switch. So, when operating HF switching to "Fixed Ant" will allow the HF antenna to be connected to the "Fixed" output terminal with the coax shield connected to chassis. Selecting LF on the ART-13 activates the PTT switching of the CU-32 and the antenna selector can be switched to "Trailing Ant" and a LF antenna used. I'm assuming that most ops are going to have a separate LF antenna such as a 200 ft end-fed wire but will use their regular HF antenna for 80M or 40M operation. 

Effective Isotropic Radiated Power  - The EIRP limit of 5 watts is somewhat difficult to determine with any accuracy. This regulation seems to be in place mainly to limit the size of the antenna versus the amount of RF power used and thus to control the effectiveness of the transmitted signal. For example, a full-size 630 meter half-wave antenna is over 1000 feet long. This type of "full-size" antenna would actually exhibit a slight gain when compared to an isotropic radiator (+1.6db.) Therefore, the power input would have to be < 5 watts to stay within the regulations (assuming there were no other losses.) With a full-size antenna, even just 5 watts input would result in a formidable signal on CW. However, small, "city-lot-size" antennae will be very inefficient at 630 meters and therefore would exhibit considerable loss rather than gain. That's how the RF power input to a "small" antenna can be very high and yet only result in 5 watts EIRP. Think of the small, inefficient antenna as acting like a "dummy load." You can input lots of RF watts and it does radiate somewhat (a few feet) but it isn't an efficient radiator. So, to stay within the regulations, one has to know the efficiency of their antenna which is determined by the antenna's input resistance and its size. From efficiency and power input you can then calculate EIRP. Antenna resistance usually has to be estimated based on several physical factors with antenna size being the most important. The best information for answering the EIRP question can be found at in their section on"630M Antennas" and "EIRP." Their formulae and examples indicate that the "average" ham antenna takes several hundred watts input to achieve 5 watt EIRP.

Propagation and Successfully Receiving LF Signals - A lot of the conversations about prospective 630 meter operation seem to be concerned about the transmitted signal. Very little is written about how to successfully receive DX signals in "real time" on the lower frequencies. Propagation on 630 meters isn't groundwave only. At night, skywave propagation dominates this region of the spectrum. It's easy to receive medium wave Airport NDBs that run 25 watts out to distances of 1500 miles. Regional NDBs that run 100 to 400 watts can be received out to the east coast. However, these great nighttime conditions don't last long. Long wave enthusiasts consider the "season" to be from the Autumnal Equinox to the Vernal Equinox, or about mid-September to about mid-March. Actually, the best part of the "long wave season" is from late-November to about mid-January. This is when the conditions are the least noisy allowing very weak signals to be heard. So, fall and winter nights or very early mornings work best on 630M. Daytime is good for testing or for local QSOs.

Your physical location is another important part of successful 630 meter operation. In noisy urban areas the RFI is so intense that virtually nothing can be heard below the AM BC band. In these locations, a shielded, magnetic loop is about the only type of antenna that might allow for some reception. These loops are shielded with a non-ferrous metal tube and, generally, the antenna only responds to the magnetic portion of the electromagnetic signal. Usually a tunable amplifier is also necessary with these loops. Since most RFI is electrical in nature, the shielded, magnetic loop provides some relief in noisy areas. Less noisy areas can usually receive DX using a remote tuned loop. These are just a fairly large coil of wire that's tuned with varactor diodes in parallel with the loop. A pick up loop is mounted within the loop field and that connects to the receiver. Usually, an amplifier isn't required on a remotely tuned loop. In quiet rural areas, it might be possible to use a wire antenna. I use both a large wire antenna and a remotely tuned loop. I find that I can always use the loop antenna. Most of the time, only winter conditions are quiet enough to allow DX reception on the large wire antenna.

For a complete write-up on how to successfully receive DX longwave signals using vintage radio equipment, go to my article "Vintage Long Wave Receivers" - use the navigation index below.

Conclusion - Today, the ART-13 is one of the "hottest" military transmitters around. It seems like everyone that has an interest in older gear, especially military gear, is looking for one or maybe even has one (or two,...or more) stored somewhere for future restoration. However, this isn't really a new phenomena,...the ART-13 has been a popular transmitter with hams for almost seventy years. Articles about converting and using the transmitter go back to the late-forties. As AM operation was replaced by SSB, the ART-13's popularity did drop but the resurgence of AM operation during the early 1990s (and the increasing interest in WWII gear) has brought the ART-13 back to prominence. Though not intended as a ham transmitter, it is interesting that so many of the WWII design approaches for this transmitter's circuit are found in later, post-war, Collins gear. The ART-13 has had a long history with hams as a versatile, potent and good sounding transmitter and today there are certainly more ART-13s "on the air" in the ham bands than ever before.


Henry Rogers WA7YBS  May, 2011, additions on dynamotors Nov. 2015, addition on restoration ART-13A sn:2054, various corrections and other additions Nov 2015,   new header photo & surplus market availability info Feb 2016, Correct knob sync info Dec 2017, added 630M info Jan 2018,


1. Various ART-13 Manuals - there are several available from BAMA

2. USAF - Radio Mechanics VOL. 1 - Extension Course 3012 - specifically on the ART-13A and the BC-348. Theory, operation, maintenance, course Q&As, informative about post-war uses and maintenance.

3. Electric Radio - N6PY Bill Feldman, article on ART-13 basics. Tells how to perform an initial checkout of an ART-13. Also, a mod on removing the "locking" current off of the Autotune motor when in standby. W6MIT John Svoboda wrote a couple of articles on ART-13 power supply design and on exactly how the loading network operates.

4. Various "Radio News" and other radio magazines from 1946 to 1950 - surplus advertising, conversion articles, prices and other information.

5. Thanks to Mike Everette, W4DSE, for many details on ART-13 history, use, repair and restoration

6. Online - MilSurplus Group, specifics on ART-13 variations by KK5F and WA5CAB

7. Thanks to W6MIT John Svoboda for the heat gun suggestion on the Multiplier trimmer capacitors

8. Thanks to the many conversations with other ART-13 users and enthusiasts that have provided so much information over the years.



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Website Navigation Index

-  WHRM History  ~  Nevada Radio History  ~  The KOWL XMTR  ~  Full Length Articles with Photos -


Western Historic Radio Museum Information
 Contact Info, Museum History 1994-2012, Museum Photo Tour, Using Photos and Info from this Website & Radio Value Info

Nevada Radio History - 1906 to 1930
Arthur Raycraft, Nevada's "Father of Wireless," America's First Radio Tour, Early Nevada BC Stations & More

KOWL's Gates BC-250L BC Transmitter
2007 Move from Lake Tahoe - Restoration - PLUS -  2013 Move to Dayton, Nevada & Getting on 160M

Parish House History
1876 to Present
Virginia City, Nevada

Lots of Photos


- Wireless Apparatus, 1920s Radio and Communications Equipment  ~  Full Length Articles with Photos -

M.H. Dodd's 1912 Wireless Station
100th Anniversary  Edition 
Includes New Photos, Reassembly Info and Lots of Original Vintage 1912 B&W Photos + Reassembly in Dayton

Universal, Intermediate Wave and Short Wave Models History, Restoration and Operation - Lots of Photos

"A Guide to the Synchrophase MU-1"
Comprehensive Manufacturing History, Restoration, Neutralizing, Performance Information - Lots of Photos


 SE-1420, IP-501 & IP-501A
"The Classic Shipboard Wireless Receivers"
Comprehensive History, Restoration and Operation Info - Tuning in NDBs with IP-501-A

Vintage Long Wave Receivers
Long Wave Receiver Profiles, Loop Antenna Info, NDB Info and Log,
Fallon NV "Master - M" Loran Station Tour



- Vintage Communications & Amateur Radio Equipment  ~  Full Length Articles with Photos -

National Co. - HRO Receiver
"The Cream of the Crop" 
Comprehensive History, Serial Numbers, Restoration, Lots of Photos & More

National Co. - NC-100 Series
"Moving Coil"  Receivers 
Comprehensive History, Serial Numbers, Restoration & More - Includes Civilian Versions, Military Versions & Airport Versions

Hallicrafters SX-28
"A Pre-war Masterpiece"

Comprehensive History, Serial Number Analysis, Restoration Details & More

Hallicrafters DD-1 "Skyrider Diversity"
Comprehensive History, Serial Numbers & Restoration Details

NEW!          Navy Dept - RCA - RAA-3 Receiver
1930s Ship or Shore Station Longwave Superheterodyne
History, Circuit Design & Construction Details,
Restoration Log with Lot of Photos

 RCA's Amazing AR-88 Receivers
Comprehensive History, Restoration Info, How to do IF Sweep Alignments, Serial Numbers & More

RCA's Legendary AR-60 Receiver
Comprehensive History, Serial Number Analysis, Restoration Details & More - including the AR-60 connection to Amelia Earhart's Disappearance

Hammarlund Mfg.Co.,Inc
The Incredible Pre-War 'Super-Pro'
Comprehensive History, Serial Number Analysis, Restoration Details. Includes info on the Hammarlund Comet Pro

Patterson Radio Company
   PR-10 Receiver & Pre-selector              
Comprehensive History, Los Angeles Radio Mfgs History, Circuit Details, Serial Numbers, Restoration Details & More

NEW!    Hallicrafters' Super-Pro, the R-274 Receiver
Comprehensive History, Circuit details with Comparison to the Hammarlund SP-600, Restoration Details, Best features of each Receiver. Yes! You can VOTE for your favorite Super Pro


-  Rebuilding Communications Equipment  ~  Full Length Articles with Photos -

Rebuilding the R-390A Receiver
Detailed Restoration Information for each module with Lots of Photos

Rebuilding the ART-13 Transmitter
Detailed Restoration info - includes details on building AC power supplies (with schematics) Lots of Photos

Rebuilding the Hammarlund SP-600
Detailed Restoration Information with Lots of Photos

           T-368 Military Transmitter                    
Detailed Information on Reworking, Testing and
Operation with Lots of Photos

Rebuilding and Operating the AN/GRC-19
T-195 XMTR & R-392 RCVR

 Detailed Information with Lots of Photos

Successfully Operating the BC-375 on the Ham Bands Today
Detailed Information on Power Set-ups that Work, Dynamic Neutralization, BC-191 Info & More

Rebuilding the Collins 51J Series Receivers
Detailed Restoration Information with Lots of Photos - Includes R-388 Receiver

Rebuilding the BC-348 Receiver
Detailed Information on all BC-348 Types, Dynamotor Retrofit Information, AC Power Supply Enhancement - Lots of Photos

Building an Authentic 1937 Ham Station
Utah Radio Products - UAT-1 Transmitter


- WHRM Radio Photo Galleries with Text -

Entertainment Radios from 1922 to 1950

Roaring 20s Radios
1922 to 1929

Vintage Table Radios
1930 to 1950

Floor Model Radios (Consoles)
1929 to 1939

Only Zenith Radios
1930 to 1940

Communications Equipment from 1909 to 1959 - Commercial, Military & Amateur

 Early Ham & Commercial Wireless Gear
1909 to 1927

Classic Pre-WWII Ham Gear
1928 to 1941

WWII Communications Equipment
 U.S. Navy & U.S. Army Signal Corps  1941 to 1945

Commercial & Military
Communications Gear
1932-1941 & 1946-1967

Post-WWII Ham Gear
1946 to 1959

Vintage Broadcast Equipment, RTTY, Telegraph Keys & Vintage Test Equipment

Vintage Microphones
 & Vintage Broadcast Gear
1930 to 1950s

Radio Teletype - RTTY - with Real Machines
includes TTY Machines, Military TUs and Amateur TUs

Telegraph Keys - 1900 to 1955
"From Straight Keys to Bugs"
Hand Keys and Semi-Automatic Telegraph Keys

Vintage Test Equipment
1900 to 1970

Includes Tube Testers, Freq Meters, Wobulators and More


Radio Boulevard
Western Historic Radio Museum

 Vintage Radio Communication Equipment Rebuilding & Restoration Articles,

 Vintage Radio History and WHRM Radio Photo Galleries

1909 - 1959



This website created and maintained by: Henry Rogers - Radio Boulevard, Western Historic Radio Museum 1997/2017