I first wrote this article in 2006, but as time progressed, so did the 1930s station. As with several of my articles, this one is always being updated. You will note that sometimes I am writing about the Utah UAT-1 in the context of a new project and then there will be an addition at the end of each section if anything new has happened. I have generally sorted this as a year by year change. I hope the fact that this article does change periodically will provide continuing interest and entertainment.

Building an Authentic 1930s Ham Station

For sometime I have wanted to put together an operational, late-1930s Ham Station with the capabilities of operating both CW and AM on the high frequency ham bands. What were only random thoughts became a real possibility when a 1937 Utah UAT-1 transmitter was obtained. The transmitter was going to require a complete restoration due to an old incomplete modification/update that unfortunately compromised much of the UAT-1's originality. Additionally, a thirties-type Antenna Coupler would be required along with a correct vintage Speech Amplifier-Modulator. The receiver should represent the best of the late thirties designs that were within the economic capabilities of a ham who would have purchased and built the UAT-1. The antenna to be used would be our already in-use 135 foot inverted vee fed with open line. Here is a detailed look at the equipment and how this authentic late-thirties station was actually put "on-the-air."

The 1937 Utah UAT-1 Transmitter

Utah Radio Products Company had been in business since the twenties mainly offering transformers and speakers for other manufacturers to use in their equipment. In January 1937, Utah announced the "Add-a-Unit" Kits. These were five different kits that were based around Kit #1, an eighty-watt, CW transmitter. The other kits included an Antenna Coupler, a Speech Amplifier/Low Power Modulator, a High Power Modulator and a High Power RF Amplifier. All five kits provided the builder with a complete 500W CW/450W AM transmitter for a little over $200.00. Each kit sold for about $50, except the Antenna Coupler which sold for $13.95. Each cabinet was designed to be bolted on top (or below) another cabinet resulting in a rather tall transmitter that was "loaded" with Utah "iron."

The advertisement above appeared in January 1937 issue of QST

Far Left: Utah Catalog Cover   Above: Inside page of catalog

The circuit of the UAT-1 is a standard crystal controlled oscillator using a metal 6L6 tube. The oscillator output is coupled via plug-in coils to the RF Power Amplifier, consisting of two metal 6L6 tubes in parallel. The PA output is link coupled via a large, 2.25" diameter, plug-in coil. A total of three plug-in coils are required for each amateur band used. The UAT-1 is capable of about 80 watts input on CW depending on the antenna and coupling used. The transmitter section is built on a steel chassis that mounts in the upper tray of the cabinet. The power supply chassis mounts in the lower tray of the cabinet and provides 600 vdc to the PA and 400 vdc to the Oscillator along with 6.3 vac for the 6L6 heaters. Choke input is used and the filtering is adequate for a good quality CW signal.

The UAT-1 Restoration

 I obtained the Utah UAT-1 in a trade with NU6AM. Jim not only had the transmitter but also its original assembly manual, original catalog and two original letters from Utah's Amateur Division Engineer, Oliver Read, to the transmitter's first owner, Franklin Schaefer, of Oakland, California. The Utah transmitter cabinet and front panel were in very good physical condition but internally the UAT-1 had been modified extensively. A former owner had wanted to increase the power output by converting the PA to 807s. Fortunately, the transmitter chassis was almost unaltered - physically - as only original holes had been used to mount the newer components. The transmitter chassis was missing most of the original parts but the original variable condensers and a few of the original sockets were still present.

The power supply was completely modified and many newer parts were now mounted on its chassis resulting in several non-original holes having been cut. Though many newer parts were installed on the PS chassis, the original power transformer and both original filter chokes were still present and functional. The best way to repair the damage was to remove all of the components and install one large "butch plate" to cover all of the holes. This was painted to match the chassis. New holes were then cut to allow mounting the original type parts in their correct location. In fact, both chassis were "stripped" of all parts so assembly could be performed "per the manual" with original type components.

Before restoration photos. Left: front shot showing that overall the UAT-1 was in good condition. Center: Inside is a different story, note 807s in the transmitter chassis. Right: Showing the highly modified power supply with extra transformers and regulator tubes.

The Utah UAT-1 assembly manual was invaluable as it provided information on exactly what parts were originally used and how Utah expected the transmitter to perform. However, like many early ham documents, the manual is vague in many of the details. This was because so much depended on the skill and experience of the builder. The Utah manual did provide assembly drawings showing suggested mounting locations for the various components but a wiring layout was not provided. The builder was supposed to know good transmitter construction techniques and follow those rules in completing the transmitter. I used vintage parts in restoring the UAT-1 with the exception of capacitors and the 25 watt wire wound resistors (the originals were missing anyway.) All new filter capacitors were mounted inside duplicate of original electrolytic capacitor cans that had bakelite screw bases for mounting to the power supply chassis. The one paper wax capacitor was built up by installing a new cap inside an old shell and then re-waxing. All wiring was sleeved in original type black varnished "spaghetti". The goal was to have the UAT-1 look and perform as if it was built by an experienced technician in 1937.

Coils and Crystals - Details

The UAT-1 did not have any correct plug-in coils when obtained. We had to wind new coils on the proper "old style" forms. Several manufacturers of the day offered these plug-in forms molded from either bakelite or R-39 material. Utah specified Hammarlund forms, although Bud, Insuline and others offered almost identical forms. The Oscillator Plate coil and the PA Grid coil are wound on a four pin Hammarlund form that is 1.5" in diameter. The PA Plate coil is wound on a five pin form that is 2.25" in diameter. All coils are wound with 16 gauge wire. Although the original specifications call for DSC (double silk covered) wire, this is difficult (if not impossible) to find in any quantity. I had to use modern, high temperature enamel coated copper wire for winding the coils. The UAT-1 manual gives all of the coil data for 160M, 80M, 40M and 20M. Additionally, I had the two letters from Utah Radio Products Co. to the original owner, one of which gave coil data for 10M. 

The UAT-1 uses crystals mounted in HC-3 type holders. These are the large, round crystal holders that fit a standard five-pin tube socket. The major supplier of the day was Bliley, although Valpey, Hi-Power and J-K (James Knight) were also popular crystal manufacturers. Luckily, I was able to scrounge around my "junk boxes" and find 21 of the proper type crystals - most of them in their original boxes. Unfortunately, most of the crystals were for odd frequencies within (and some outside) the ham bands of today. Out of the 21 crystals, I found only one 40M crystal and two 80M crystals that were inside the currently popular CW section of the bands. I decided that some experimenting was necessary if the larger portion of these crystals were going to be useable. Early crystals (and FT-243 holders) can be easily disassembled and the crystal removed from the holder. Since the frequency is determined mainly by the thickness of the crystal, grinding the crystal was the usual method to alter the frequency. Since grinding removes material, this process will raise the crystal frequency.

I found several military FT-243 type crystals in the 6MC region that I disassembled to remove the crystal. Using 320 and 400 grit oxide paper and water, these crystals were ground up to the CW portion of 40M. Grinding can be done with the oxide paper placed on a flat surface and water used as a lubricant. Precision grinding can be performed on a sheet of glass using fine carborundum grit and water, though experience seems to show this is unnecessary. When grinding, rotate the crystal in a "figure-8" pattern to keep the removal of material even. Also, grinding both sides of the crystal will help keep the removal of material somewhat even. The test jig was an HP-606 Signal Generator with a digital frequency counter and a Tektronix oscilloscope. After a few minutes of grinding, the crystal had to be assembled into the holder I intended to use (the round HC-3 type) and the crystal tested for its active frequency. When the crystal frequency was within about 100 KC of the desired frequency, the grit was changed to 400 or 600. The output (activity) of the crystal depends on how fine (and symmetrical) the finished grind is, (too rough and the output will be very low and the active frequency erratic.) I used the fine grit to grind the crystal to the desired frequency. The type of holder and the length and width of the crystal don't affect the operation. The thickness, the fineness of the finished grind and cleanliness of the surfaces are what is important in this process. Ultimately, I ended up with several usable crystals with correct vintage holders for both 40M and 20M CW and 80M phone.

Left: The coil set for 40M wound on Hammarlund forms.   Right: Various HC-3 type crystals with original boxes.

Initial Testing of the UAT-1

Initial set-up of the UAT-1 requires that the 100 watt adjustable divider resistor in the power supply be set for 400 vdc to the 6L6 Oscillator with 600 vdc applied to the PA 6L6s. After this, a quick dip of the Oscillator current using the OSCILLATOR TANK control will have the oscillator running at the crystal frequency. The resonance curve will not be symmetrical. Choose the side of the curve that is wider and set the oscillator current for about 20mA.  Next, close the sending key and quickly dip the PA Plate current (right-side meter) using the P.A. PLATE TANK control. The plate current will be low at resonance, ~75mA. This is followed by increasing the PA Grid current using the P.A. GRID TANK control. This also requires switching the left-side meter by moving the phone plug cable from the CRYSTAL OSC. GRID current jack to POWER AMP. GRID current jack in order to read PA grid current. Increase the PA grid condenser (reads higher on the scale) until the PA Plate current reads about 100mA to 125mA. Then check the PA Grid meter and it should read around 5mA. Re-dip the PA PLATE TANK and the transmitter is then tuned to resonance for the particular coils and crystal installed.

With the initial tune up it is necessary to neutralize the PA. This is a rather easy procedure using a "dummy" plug to remove the plate and screen B+ and then tuning the plate through resonance while watching the PA grid current. The neutralizing condenser is insulated and mounted to the rear chassis of the transmitter. Originally, the condenser was a shaft adjustment but since the original condenser was missing, I used a recessed, screw driver adjustable shaft condenser of the correct value when rebuilding the UAT-1. Add just enough capacitance to stop any movement in the PA grid current while tuning through resonance and the PA will be neutralized.

With link coupling, the loading on the PA Plate depends on the coupling to the antenna or load. Generally, the greater the coupling the more plate current at resonance and the greater the power output. The Utah letters to the original owner, Franklin Schaefer, imply that he was having difficulty loading the UAT-1 with just two turns on the link. Oliver Read,  the Amateur Radio Division Engineer at Utah, suggested in one letter to increase the link to three or four turns to increase loading current. Read also mentions that the antenna coupler should have three to four turns on its link. I wound the 40M and 20M PA Plate coils with a three-turn link spaced below the PA tank coil and found that I had ample coupling available. However, on 80M more coupling was necessary for proper loading. I used a plastic coil form that just fit over the PA tank coil winding and then wound a three-turn link on that. I used flexible wires for the link connection to the pins on the coil form. This arrangement gave the necessary coupling for full output on 80M and resulted in good AM phone modulation. For CW operation, the design of the UAT-1 has the Oscillator running all the time and just the PA is keyed. This results in some "back wave" but it is not radiated any great distance. Although one can directly couple from the output link to an antenna cut for a specific frequency, an Antenna Coupler would provide greater versatility along with additional harmonic suppression. We decided to build an authentic Antenna Coupler similar to the one that Utah sold as Kit #3.

The Antenna Coupler

The Utah Antenna Coupler was a fixed-link, series-parallel type tuner with individual condensers, RF watt meter and a switch for selecting series or parallel tuning. Since the link in the transmitter is also fixed, the operator would have to experiment with the number of turns on each link for best loading of the transmitter. This would be acceptable if only one band were going to be used but I wanted the UAT-1 to operate on 80M, 40M and 20M. I decided to build a swinging-link that would allow for some adjustability of the loading. Also, in keeping with the typical late-thirties Ham station construction, clips were used for both turns selection on the inductance and for series/parallel switching. Finding a suitable housing was not difficult as it was discovered an old BC-348 cabinet has almost identical width and depth dimensions. By using the BC-348 cabinet's back as the front an "open-in-the-rear" cabinet results. I used a masonite front panel (black wrinkle finished) for the proper look and to cover the old holes in the metal cabinet. I found a matched pair of 25pf to 125pf transmitting variable condensers in my junk box. These were mounted directly to the masonite after rectangular openings were cut in the aluminum. This allowed the condensers to be insulated from chassis or ground. The junk box also turned up a large diameter tuning inductance that I mounted using wooden dowels. The swinging link was another junk box item that was modified to mount to the cabinet. The RF amp meter has a 0 to 1 RF Amp range. The meter is connected through one of the feed lines and provides an indicator that RF is getting to the antenna. The actual reading is not important as variables like antenna impedance or SWR will affect the RF current. The RF Amp Meter is only for a maximum output indicator. When operating the coupler in parallel the RF Amp meter will read very little current since this arrangement is low current at the feed point. In series, the current is usually about .6 Amps at full output. The completed cabinet was given a black wrinkle finish and bolted to the top of the UAT-1 using the original mounting holes provided. The link connection between the UAT-1 and the coupler is via period twisted feed line. The antenna feed line connects to porcelain insulators mounted on top of the coupler. I used National Type O dials to provide the nickel-plated scales along with knobs that were identical to those on the UAT-1. A vintage metal  "ID plate" (ANTENNA CURRENT) similar to those used on the Utah transmitter was mounted below the RF Amp Meter. This resulted in an antenna coupler that was a good physical match to the UAT-1. The coupler provides versatility to the UAT-1, allowing it to operate on 80M, 40M and 20M with a good match to the 135' center-fed Inverted Vee antenna used.

The UAT-1 and Antenna Coupler - 2006 to 2007

For 2007, I wanted to eliminate the need of separate antennas for receive and transmit. I decided to add an antenna relay and receiver stand-by relay inside the coupler for easier operation when going from receive to transmit along with better receiver performance. I used old Potter-Brumfield external contact, open frame relays for appearance and ease of connecting the twisted feed lines. The receiver's twisted feed line is connected to bakelite ANT-GND terminals mounted on the side of the coupler. The relays are controlled by a separate, vintage (homebrew) 24vdc power supply that is mounted in front of the operating position and has a "Transmit-Receive" switch on the panel. I used more of the vintage ID tags on this device for the appropriate matching appearance. The advantage of using the "transmitting antenna" as the receiving antenna was the primary reason for adding this function to the coupler. Several tests revealed that no matter what matching devices were used between the receiver and the old original end-fed wire receiving antenna, nothing performed as well as using the transmitter antenna coupler with the 135' center fed inverted-vee for the receiver antenna.   For 2008, I added a ceramic switch to the Antenna Coupler for the "Series-Parallel" function and a dual-deck ceramic switch for a five position adjustment on the various taps on the antenna coil. This has resulted in much faster and easier adjustment of the transmitter and coupler together. I installed small black pointer knobs on the switch shafts. I also replaced the RF Amp meter with an older meter that was the same type used in the original Utah coupler. Though the new coupler still doesn't look much like a Utah unit, it does adjust much easier now.

Rear view of the UAT-1 for 2008

The Speech Amplifier and Modulator

The "Add-a-Unit" Speech Amplifier-Modulator #2 Kit used push-pull 6L6s run in Class A-B rated at 60 watts. The various inputs allowed for crystal microphone, phonograph input and a 200 ohm input. Meters monitored the P-P 6L6 plate current and screen current. The modulator chassis was mounted in the upper tray of the cabinet and the power supply was in the lower tray. Just how many of these #2 Kits Utah sold is unknown but certainly very few survive. I decided rather than spend an eternity looking for the Utah modulator, I would build a correct vintage unit. I had the remains of an old homebrew rig that had a suitable UTC CVA-1 Vari-match Modulation transformer rated conservatively at 30 watts. This homebrew unit furnished the chassis, front panel, current meter, filter choke and the modulation transformer. All the remaining parts were scrounged out of my "junk boxes."

I used a circuit that combined the 1939 ARRL HB 50W Modulator and the 1946 ARRL HB 40W Modulator. The two circuits are virtually identical except 6J5s are used in 1946 instead of 6C5s and the bias for the 6L6s is supplied by a 22.5 vdc battery in 1946 instead of an external negative power supply. The early version modulator has no shaping of the audio so no doubt the bandwidth of the AM signal would have been very wide. The 1946 version has some low frequency roll off but nothing for the higher frequencies that affect bandwidth. I just added a couple of capacitors in the second audio amplifier to bring the high frequencies into a 3db roll off around 3KC to 4KC. The circuit layout had to be rearranged from the original homebrew modulator layout to provide ample separation between the low-level audio and the power supply. Ample shielding was also used in the construction to assure that no hum got into the low-level amplifier stages. I used a matching knob for the audio gain control and also added several of the vintage metal ID tags for a nice matching appearance. The completed modulator looks like it is from the late thirties era and, most important, it has the "late-thirties AM sound." 

To run "phone" on the UAT-1 it is necessary to remove the telegraph key plug from the "KEY" jack and insert the plate meter cable and plug. Then insert the plug and cable from the modulator into the POWER AMP. PLATE current jack. This connects the modulation transformer between the UAT-1's 600 vdc B+ and the RF Choke/PA Tank Coil/PA Plates. Connecting the meter cable to "KEY" allows the plate meter to read total cathode current.

Above: The modulator's front panel appearance 2006 - 2007.     Right: View of the chassis 2006 - 2007.

 For 2008, I decided to rebuild the modulator into another BC-348 cabinet so the entire transmitter could be "stacked" as was the custom in the 1930s. I had an old BC-348 cabinet that was in really bad shape with lots of extra holes drilled in it, so I didn't feel too bad about using it for this project. I used a piece of masonite for the front panel and painted it black wrinkle finish. The panel was mounted to the back of the BC-348 cabinet which then became the front of the modulator cabinet. I did the same thing when building the antenna coupler. It was lucky that the original chassis that I had used for the first modulator fit into the BC-348 cabinet. I did have to lower the rectifier socket below the chassis so there would be clearance for the 83 rectifier tube. Also, some of the minor layout problems were corrected. During the rebuild, a couple of non-soldered joints were found - hmmm, how'd that happen? Well, good crimp joints work fine for a while, I guess. I used the same ID tags. Circuit-wise, I changed the audio shaping by moving it to the next stage in the audio chain so it would not be installed on a grid circuit. The battery shown in the old photo was bad. The photo below shows the new battery made from 15 AA batteries connected in series for -22.5 vdc bias. Other than that, the modulator was still the same as before. The new appearance is much better and more authentic looking.

Left: Modulator Front Panel 2008         Right: Rear View of Modulator

The 1937 Hammarlund 'Super-Pro'  SP-100X  Receiver The station receiver for 2008 is the fabulous 1937 Hammarlund SP-100X, an incredible performer that was certainly the most expensive receiver that was generally available to well-to-do hams. Whether the ham who would have purchased a $50 kit transmitter such as the UAT-1 would buy the 'Super-Pro' as his station receiver, at $400 list price, is debatable. Probably not. But, the SP-100X was available from the major discount dealers for about $250, only a little more expensive than the National HRO receiver, at $200. Besides, I had always wanted to use this receiver "on-the-air" and, after the total rebuild, there was virtually no excuse not to. The rebuild of this great example of the 'Super-Pro' entailed restuffing all of the original Cornell-Dubelier "Tiger" paper-wax capacitors. Since about half of the old original caps had been replaced in the past, I had to locate about 18 "Tiger" caps that were the correct value and these were used for rebuilding our capacitors. Nine of the 35 caps are "hidden" in the Tuning Unit and in the Detector Output Transformer and the AVC Output Transformer. Total disassembly is the easiest way to do all of the rework on the 'Super-Pro.' A few resistors were replaced and all of the grid leads for all of the RF, IF, AVC and BFO tubes had to be replaced as the original rubber had deteriorated beyond restoration. New rubber insulation was salvaged from an old telephone cable since it was the correct color and material. The Sensitivity pot had to be replaced but we used an original replacement pot that was salvaged from a "parts set" SP-200 'Super-Pro.' Finally, after reassembly the receiver was aligned and tested. For more details on this restoration, go to "The Incredible Pre-War 'Super-Pro'" article, a navigation link is at the bottom of this page in the Index.

 
The Completed 1930s Ham Station

The complete 1930s Ham Station is set up in the Vintage Ham Shack of the Western Historic Radio Museum. We are cramped for space but we did manage to fit everything necessary into an area approximately 48" wide and about 40" tall. Each year we have been setting up different receivers with the station. For 2008, we are using the 1937 Hammarlund Super-Pro SP-100X along with the Hammarlund Comet-Pro receiver from 1934 operating with a 1934 PEAK Pre-selector. I've aded a wall mounted knife-switch to allow routing the station antenna to either the SP-100X or to the Comet -Pro. Mounted under the shelf is the station relay control power supply and transmit-receive switch. The telegraph keys are a Les Logan Speed-X Model 321 hand key and an old Vibroplex Original bug. The microphone is a 1937-style Astatic D-104 (with large case and large ID tag) mounted atop an unusual nickel plated stand with adjustable "tilt back head" feature. The QSL cards are 1930s vintage.

The station feed line had to cross the ceiling of the Vintage Ham Shack to connect to a knife-switch arrangement that allowed selecting either the 1940-50s station or the 1930s Station to feed the 135 ft inverted-vee transmitting antenna. I built an insulated support for the open feed line to cross the ceiling without sagging or changing dimensions. The feed line itself is built from 14 ga. copper wire with plexiglass rods for spacers. The spacers approximate 450 ohm line and give the whole structure a vintage appearance.

Operating the station is a lot of fun and gives one an appreciation of what hams of the thirties endured for a normal QSO. If you enjoy constant "tweaking" and "tuning" - this station provides ample opportunities for both. However, it is a real thrill when an answer to a CW CQ is received and the signal report comes back from an "out of state" station - "RST 589." CW operation is usually on 40M around 7085KC or 7049KC. AM operation is normally on the West Coast Saturday Morning AM NET on 3870KC. As all AM operators already know, you are never satisfied with the AM quality of your own signal and this station was no exception. When we first got the station "on-the-air" in 2006, we actually were getting reports of "weak modulation" or "audio challenged." Although monitoring the signal by listening through a receiver and earphones indicated that the audio sounded okay, actual "on-the-air" reports were a different matter. When an oscilloscope was used to monitor the signal it became very apparent that the modulator was "clipping" and only allowing about 30% modulation. A check of the 6L6 modulator tubes' grid bias under operating conditions showed that the -22.5 vdc bias battery must have had a high internal resistance as the grid voltage was following the audio drive voltage rather than keeping the grids at a fixed bias. Installing a new -22.5 vdc battery (made from 15 AA batteries in series) cured the problem and allowed for full modulation. Current audio reports are now positive and complimentary. In the future we may change receivers or add more vintage accessories to the station. See below for past photos of the station configurations. As always, the goal will be to keep to the late thirties time period and operate a station that is enjoyable to use and interesting to listen to over the airwaves.

The 1937 Station in 2006   The station used a 1937 RME-69 receiver with a matching DB-20 preselector and a matching RME speaker. The receiver was totally restored as was the preselector. All paper-wax capacitors were re-stuffed so the under chassis appearance remained original. A full alignment was performed and the receiver/preselector combination seemed to work great. It was then noticed that signals on band 3, which covered the 80M ham band, registered much less on the "R" meter than the ham signals on band 4 (40M.) During the rebuild, I had to repair the RF coil for band 3 which entailed rewinding a new coil. Even though the same number of turns of the same gauge wire were used, it was obvious that there were losses in the rewound coil. The RME-69 doesn't have any trimmers in the RF or Mixer stages and provides a "Compensator" control to keep these stages peaked for the tuned frequency. When the RME-69 was originally built, "pre-tuned" coils were installed so that everything would track and the Compensator would work correctly on all bands. The factory "tuned" the original coils by "pushing turns." The coil that I rewound, though physically correct, was not tuned exactly to the required inductance and therefore some loss in signal strength resulted and could not easily be corrected for. The only solution was to find another RME-69 RF coil for band 3 (this coil form also has the RF coil for band 4 on it.) Advertising was fruitless, so after a year I decided to prove to myself that my analysis of the problem was correct. I had another RME-69 that could provide the necessary coil but I didn't want to just "steal" it from a fairly nice receiver (even though it was painted blue.) I was sure that I wasn't going to ever actually use the blue RME-69, so a coil swap seemed to be a solution that didn't harm that receiver, too much. I certainly did want my black 1937 RME-69 to function absolutely correct on all bands. The actual swap only took about two hours to perform even though some major disassembly is required to get at the coils. The test with signal generator was promising but actually connecting the antenna and listening to 80M proved that the coil swap was the necessary solution. Now the RME-69/DB-20 performs fantastic on 80M with many of the high power AM ham signals pushing the "R" meter almost all the way to the top. Before the coil swap meter never got above R-5 on band 3. All other bands still are equally sensitive as before. In the future sometime, I may re-install the RME-69 as the station receiver as it is an excellent performer now.

The 1930s Station in 2007   Since we had less than desirable results with the RME-69 at first, we decided to go with a different receiver for 2007. Our receiver for this year was the fabulous 1935 National HRO. An incredible receiver that was super sensitive and also had impressive audio. Only once and a while was QRM a problem and then the Crystal Filter was quite good at removing the offending signal. The matching National speaker along with several HRO coil sets some of which are mounted in the original National coil box were included in the station. Also visible is the older style 5897 power supply for the HRO receiver. This is actually for the FB-7 receiver but was the type usually provided with the early HRO receivers. Later I swapped supplies and used an even earlier 5897 that went with an SW-5 type receiver. It was pretty well trashed so I rebuilt it into the ultimate HRO power supply with triple filtering. It provides the correct voltages for the HRO at the receiver, compensating for the IR drop across the power cable. This is one of the reasons that this HRO performs so well. The details of our authentic restoration of the HRO receiver is on the "National Co.- HRO Receiver" webpage, navigation link below. For 2007, we also added the send/receive relays into the UAT-1 antenna coupler and built a vintage power supply to operate the relays. This power supply is under the HRO on the table. We use this as our transmit-receive switch. By using the same antenna for transmit and receive, the performance of the HRO was significantly improved. Also added, the National CRO 3" oscilloscope monitor. This unit is all original and though in pristine condition with a good CRT, it has the usual capacitor problems that create trace distortion. Rebuilding it to correct the problems would destroy the excellent originality of this example and I probably would not have used it anyway. The nickel-plated, "spoon shade" lamp is a period piece that really enhanced the appearance of the station. We operated the 2007 version of our 1937 station many times on the Saturday Morning AM Net on 3870kc, always receiving nice audio reports and copy via the HRO was always a pleasant experience. We also had the "Utah to Utah" sked with K7RLD in 2007. Possibly the first UAT-1 to UAT-1 qso in several decades. Details below.

The 1930s Station for 2008  This year the 1930s station has a revamped UAT-1 with rebuilt modulator and rebuilt antenna coupler. Both of these projects have resulted in the transmitter now appearing more like a 1930s unit. The changes have made the transmitter much easier to adjust, too. I have added two Hammarlund receivers - our 1937 Hammarlund 'Super-Pro' SP-100X and our 1934 Hammarlund Comet "Pro" receiver operating with a 1934 PEAK preselector. The Comet "Pro" was a popular receiver in the mid-thirties and would have been a likely predecessor to the 'Super-Pro' as a station receiver. The power supply that functions as our T-R switch has been moved and is now bolted under the shelf for better access to the switch. The large speaker on the top shelf is for the Hammarlund 'Super-Pro' and is a 10" Hammarlund speaker but it was originally for the HQ-120X. Since the output Z on the SP-100X is 8 ohms, I can use this speaker with no matching transformer and it is a genuine Hammarlund product - besides, it sounds wonderful. The bakelite speaker is 30s vintage and is used with the Comet "Pro." The knife-switch on the wall allows station antenna routing to either the 'Super-Pro' or the Comet "Pro" receivers. Other items are the National SW-3 stand-by receiver, the black bakelite RCA ashtray, the plug-in coils for the transmitter and for the Comet "Pro", the transmitter crystals are on top of the UAT-1, also vintage tube boxes, a Bliley Amateur Frequency Chart and 1930s vintage QSLs. We changed the Logan bug for a Vibroplex Original. In addition to all of the equipment changes, we also built a new table for the station. The old table was too small to hold the 'Super-Pro' and also we were cramped for space when sending CW. The new table has a Masonite top and measures 48" by 24." Since the station now uses equipment dating from 1931 up to 1937, I changed the designation to a "1930s Station."     Above:  The feed line across the ceiling

The Historical "Utah to Utah" Sked

 Copyright © Henry Rogers W7HTR, Western Historic Radio Museum - APR 2006, updated DEC 2006, FEB 2007, MAR 2008, JUL 2008

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