Post-WWII Ham Gear

Radio Boulevard
Western Historic Radio Museum

 
WHRM Radio Photo Gallery
 

Post-WWII Ham Gear
1946 to 1960

 Amateur Radio Receivers
 and
Amateur Radio Transmitters
 


 

I1LOV, Augusto Lovisolo, Varese, Italy  (ca:1958) with Collins KWS-1 and 75A-4  (photo from his QSL card.)

Post-War Ham Gear -  1946 to 1960

National Company Inc.  -  HRO-5A1 

At the end of WWII, most manufacturers had been building for the war effort since 1942. They didn't have anything new or ready for production for the 1946 model year. National offered the WWII version HRO-5 in late-1945 as their new table model receiver. The HRO Senior had evolved through WWII but by the end of the war, it still didn't look very different than the old pre-war receiver. The major changes during the war involved the crystal filter design, the changeover to metal octal tubes, a new non-ventilated cabinet and the use of mostly JAN parts. These late-WWII receivers were designated as the HRO-5 and the HRO-W. The first HRO-5 receivers offered after WWII were models that didn't have the bandspread coil sets. In a short time period (probably by 1946,) bandspread was added to the A, B, C and D coil sets and the receiver designated as the HRO-5A. As with the late-WWII coil sets, the post-war coil sets used a single aluminum plate with silk-screened graphs. Many of the HRO receivers sold by National in the early post-WWII period will have several variations that seem to confirm that National was trying to "clear out" old stock. Many post-WWII HROs will be found with pre-WWII S-meters installed. Several front panels have turned up with extra holes for the long data plate used on the HRO-W. Expect to find many variations when examining HRO-5 receivers sold up to about mid-1946. By mid-1946, the HRO-5A1 replaced the HRO-5A and added a noise limiter to the circuit. When the receiver was in a table top cabinet it was designated as the HRO-5TA1 (rack mounts were HRO-5RA1.) The HRO-5A1 used 12 tubes - two additional tubes were necessary for the noise limiter circuit. Early versions of the HRO-5A1 may be found with the round S-meters, earlier surplus front panels which will have the National HRO-5A1 tag mounted just above the Noise Limiter control and many other minor variations that show that National was still trying to clear out old stock. The last of the HRO-5A1 receivers will have a square S-meter, cadmium-plated chassis, a stepped-switch Crystal Filter Selectivity control and rubber insulated wire under the chassis in the wiring harness. The late versions of the HRO-5A1 receivers seem to be consistent in construction and use of new parts and components. The HRO-5TA1 shown in the photo above is a very late example with a production run code of 184.

In late-1946, an HRO-6 was produced in a very small production run that used the same numerical designation as the HRO-5A1 production run, 184. It appears identical to the HRO-5A1 externally and the only difference between the two receivers is a slight change to the Noise Limiter circuit. It's likely that the actual change in the Noise Limiter is that it was built directly onto the chassis instead of being built on a small chassis that was mounted on top of the receiver chassis. It's possible that National designated the HRO-5A1 receivers built after July, 1946 as the "HRO-6" for a short time. Considering that the ham consumers might assume that the HRO-6 would be National's "new 1947 model" and that National was actually doing the design work for the HRO-7, the HRO-6 designation was quickly changed back to HRO-5A1. National apparently didn't want the hams thinking that their new receiver looked just like the pre-WWII HRO receivers.

For 1947, the HRO-7 was introduced and this receiver totally changed the appearance of the black wrinkle finish HRO. The HRO-7 was light gray smooth finish, the cabinet was modernized with rounded corners, the S-meter was mounted behind the panel and viewed through a cut-out and the knobs were restyled. The matching speaker was also restyled to match the new HRO-7's appearance. Internally, a voltage regulator was added and the LO changed to a 6C4 miniature tube. Coil sets were changed to not employ handles for removal and levers were utilized. Additionally, the graphs and charts were replaced with a linear calibration scale. Although the physical appearance of the HRO-7 changed dramatically, internally most of the updates to the HRO-7 were rather conservative.

 

NC-204D from 1946

National Company, Inc. - NC-240D (aka: NC-2-40DT or DR)

National's "Moving Coil" receivers utilized a cast-metal catacomb that carried the various front-end coils and placed them into contact with the tuning condenser by way of small contact pins and pin-receiving contacts. The catacomb was rack and pinion driven with a large knob on the front of the receiver. The initial "Moving Coil" receiver was the 1936 NC-100. In 1940, the NC-200 was introduced and it featured both general coverage coils and amateur band spreading coils. During WWII, National produced the NC-200 receiver for various uses. However, like most military receivers, the amateur band spread function was eliminated. These receivers were designated as the NC-240CS. Immediately after the war ended, National did sell some NC-240CS receivers to the civilian market but most were considered "commercial" receivers. The NC-240CS was also used as an Airways Receiver designated the RCR. In a short time, National reinstalled the amateur band spread and designated the new receiver the NC-240D although some ads and manuals show the model as NC-2-40D. The NC-240D added metal pedestal feet to the receiver cabinet. The single large knob that provided tuning when pushed in and changed bands when pulled out was unchanged from earlier versions of the NC-200 series. Initially, the NC-240D was supplied with the round flange Marion Electric S-meter, which was the same S-meter used in many pre-war National receivers including the HRO Senior. By 1947, the round flange meter was replaced with a square flange S-meter, also from Marion Electric. Note in the photo above, the NC-240D dial has all of the Band Spread scales near the center of the circular arc of the dial. Later NC-240D dials will have the Band Spread scales directly above the A, B, C and D General Coverage bands (see lower photo.) Production of the NC-240D continued through most of 1948. The NC-240D was the last of the "Moving Coil" receivers produced by National - a design that was produced from 1936 up through 1948 and including the famous WWII RAO line of Navy receivers.

The NC-240D is a single preselection receiver with two stages of IF amplification. A Crystal Filter is provided as is a Noise Limiter and a Tone control. The audio output is from push-pull 6V6 tubes but the audio circuitry utilizes a phase inverter rather than an interstage transformer (National began using the phase inverter circuit with the NC-200 in 1940.) The matching speaker (also with chrome bars and pedestal feet) had the P-P audio output transformer mounted to the frame of the 10" Jensen speaker (so, ideally, each NC-240D should have its matching speaker included in the sale nowadays.) The phone jack on the left of the front panel is for headset operation while the phone jack on the right is an audio input (for phonograph or similar device.) Since National had lots of "left-over parts" from the war production, the early versions of the NC-240D do have many small variations from receiver to receiver (just like the HRO-5.) The chassis appears to have been punched for many variations so expect to find almost any NC-240D to have unused large holes in the chassis. By the later versions, most of the parts are standardized and the receiver produced was consistently the same.  National used "T" in the model number to indicate that the receiver was in a table cabinet while "R" was used for the rack mounted version.

The NC-240D can be an excellent vintage receiver in a vintage ham station. The receiver is fully capable of excellent sensitivity and can cope with just about any type of QRM. The audio reproduction is excellent if the original loudspeaker is used. A full rebuild is usually necessary followed by a complete IF and RF alignment to achieve the performance that these receivers are capable of providing.


photo above: NC-240D from 1948 (last production run) showing how the late-builds look.

 

the Hallicrafters, Inc.  -  S-38 Series

The S-38 was a post-war continuation of the "introductory" type receiver line, characterized by the pre-war Sky Buddy series. Intended for the beginning ham or shortwave listener, the S-38 was low-priced, easy to operate and most users were able to get good performance results considering the receiver's circuit limitations. Introduced in 1946, the initial S-38 had six tubes with Bandspread, BFO and Noise Limiter circuits. All of the S-38 series receivers were AC-DC operated. Shortly after its introduction, the circuit was changed to a five tube set with no noise limiter and a CW position that used a gimmick to actually set-up a regenerative oscillation in the IF. There certainly must have been complaints about the performance of these later S-38s since CW is next to impossible to receive with the IF amplifier in oscillation. The gimmick used was a length of wire under the chassis that is moved around until the regenerative oscillation seems like it might allow CW copy. Needless to say, most youngsters were listening to SW BC and hams on AM phone anyway (unless they wanted to become hams - then good CW performance was important.)

S-38 versions A, B and C have semi-circular dials while the D and E versions have slide-rule dials. Selling price was around $40 in 1946 but by production's end, in 1961, the price had climbed to $55. The first version cabinet was designed by Raymond Loewy, though Loewy actually won an award for the SX-42 cabinet design.

Also available were two custom finish S-38E models. These were the S-38EB, a blonde faux finish version and the S-38EM, a faux mahogany finish version (shown to the right.)

Lafayette - KT-200 - aka: Trio HE-10 or "S-38 Look Alike"

If you really loved Raymond Loewy's original S-38 exterior design BUT you knew that the circuit of the S-38 just wasn't capable of "on the air" communications AND you didn't mind spending a little bit more money AND you also didn't mind assembling your new receiver, then you could invest in the Lafayette KT-200.

In 1959, Lafayette began selling a receiver kit that was designed and produced by Trio of Japan (later to become Kenwood.)  The KT-200 was essentially the Trio HE-10 in "kit form." When assembled, the receiver actually provided the new owner with a receiver that was capable of "on the air" communications. With a tuned RF stage and two stages of IF amplification along with bandspread tuning, an S-meter and an AC operated power supply, the KT-200 was pretty much a standard "ham receiver." The superheterodyne circuit used nine tubes and was "miles ahead" of the S-38 in performance. The KT-200 also had a real BFO and could copy CW without too many headaches. The receiver front-end and IF transformers came "pre-aligned" to ease assembly and final testing. As would be expected, dial accuracy was vague at best. For about $70 and a few hours of assembly and final testing, the new KT-200 owner had a receiver that looked like a Raymond Loewy creation and performed adequately whether he was a Novice ham and or a frugal but experienced ham. Some users would add a Q-multiplier to help with selectivity. There was also a matching loudspeaker available. The KT-200 was available from 1959 up to about 1964.  

 

the Hallicrafters, Inc.  -  SX-42

The SX-42 was introduced in mid-1946 as the post-war successor to the company's former "flagship" - the SX-28A. The SX-42 was a complete departure from the usual receiver styling of the time. Well-known industrial designer Raymond Loewy created a receiver exterior that didn't look like any piece of radio gear that had proceeded his futuristic, award-winning design. The main tuning escutcheon with its green tinted plastic and green main tuning dial resembled something from under a then modern jet canopy. A coaxial tuning system allowed the user to "lock" either the main tuning or bandspread tuning depending on which was going to be used. Besides the ultra-modern exterior, the receiver circuit boasted a very wide frequency coverage of .54 to 108MC with the addition of Frequency Modulation capabilities from 27 to 108MC. The receiver used 15 tubes like its predecessor the SX-28A did but a Converter tube is used rather than separate LO and Mixer tubes. Additionally, a VR tube was included along with Limiter and Discriminator tubes for FM. The SX-42 was single-conversion with double pre-selection on all bands (except band 1, AM-BC) using two seven-pin miniature tubes for RF amplifiers (6AG5 tubes.) Four Loktal type tubes were also used in the circuit and the remaining nine tubes were standard Octal types. The audio circuit used P-P 6V6 tubes and provided 500Z ohm and 5000Z ohm outputs. Selling price was $250 but, by 1947, the price increased to $275. There were several matching speakers available but the R-42 table-top bass-reflex speaker is generally pictured with the receiver in Hallicrafters' advertising. Another accessory was a table top "Tilt-Mount" on which the receiver was placed. The Tilt-Mount then allowed the entire receiver position to be moved in any angle to allow a comfortable view the receiver front panel. Early versions of the SX-42 will have a greenish colored bezel on the bandspread dial and a black background "h" emblem on the dial. Later versions have a light gray bezel on the bandspread dial and a silver background "h" emblem. The are a multitude of engineering upgrades to the circuit and manufacturing process all through the SX-42 production.

The SX-42 was really never a very popular receiver with hams. Certainly the expense of the receiver was an important issue for many but its unusual looks, which hams may have been considered "too modern" in the then age of "wrinkle finish black panels," may have also been a factor. The coverage of the then new FM band (88 to 108MC started in 1946) may have made hams feel that the receiver was more of an expensive luxury for the well-to-do consumer than for a typical budget-minded ham. At any rate, production of the SX-42 was stopped in early 1948 - a fairly short lifespan for a "flagship" receiver. The SX-62 took the SX-42's place as the high-end Hallicrafters receiver but it seemed to again be more for the consumer market and few hams bought them as their station receiver. The popular SX-71, certainly designed for hams, filled in that portion of the ham communications receiver market after the demise of the SX-42.

Today, the features that resulted in the SX-42's only moderate success are what attract collectors to the receiver - the futuristic styling (which won an International Design Award for Raymond Loewy from the NY Museum of Modern Art,) the wide-swing FM-BC coverage, the fabulous audio (when using the proper Z speaker) and the receiver's scarcity all contribute to the SX-42's desirability. Additionally, the SX-42 is featured in a plethora of late-forties "B" movies, from Gene Autrey shows to low-budget science fiction movies, so SX-42 fans can regularly spot their favorite receiver in a multitude of film backgrounds.

Shown in the photo to the left is a later version of the SX-42 along with the matching R-42 bass reflex speaker. This combination was purchased for K6HUZ by his father as a special gift for passing the General Class license exam. It was 1954 and the SX-42 and R-42 were found in a pawn shop not far from the Federal Building, where the FCC administered the amateur exams, in downtown Los Angeles. K6HUZ kept the receiver and speaker in great condition for 57 years, then donating it to our museum.

The photo above in the header shows an earlier version of the SX-42. I found this receiver in a backyard shed in Carson Valley, Nevada. It had been the victim of poor troubleshooting and had several modifications to the circuit trying to correct a fundamental mis-wire that happened when the filter capacitors were replaced. I had to strip out the IF section of the receiver and rebuild it to stock. I went ahead and fully re-capped the receiver. It now works fabulously with great audio and respectable sensitivity. I have yet to have the "gun metal dark gray" paint matched so I can restore the cabinet on this early version SX-42

 

Collins Radio Co.  -  75A-1 

Art Collins began selling amateur transmitters in the early thirties. High quality and great performance brought in commercial and military customers making Collins Radio a major supplier of radio equipment during WWII. Collins entered into the communications receiver market after WWII with a double conversion superheterodyne receiver that was entirely permeability tuned. Using a precision Permeability Tuned Oscillator (called a PTO - Type 70E-7) along with a multiple crystal controlled oscillator and by keeping the maximum coverage of each band to just 1.0 MC, Collins was able to achieve 1.0 KC accuracy in the dial read out with receiver stability that was incredible. The linear dial system features "band in use" illumination and requires twelve #328 lamps - two lamps for each band. The 75A was an introductory model that was probably not produced in any quantity. It was superseded by the 75A-1 in 1947 - the only noticeable difference was the addition of a Noise Limiter circuit with a front panel switch. Though the 75A-1 is a 1947 design, the receiver's performance is a pleasant surprise - more like a receiver from the 1960s with impressive stability, dial accuracy, sensitivity and selectivity. The 75A-1 is a first-class receiver for a vintage ham station with performance that is still competitive, even on 10 meters. Audio in the AM mode may be considered somewhat restricted due to the 75A-1's excellent selectivity but, after all (using the CCA argument,) it is a communications receiver.

 

Collins Radio Co.  -  32V-2

The 32V-2 transmitter was introduced in 1948 and had some improvements over its predecessor, the 32V-1. The new transmitter redesigned the Pi-network so that it could be fully adjusted with the front panel controls. The V-1 design required lifting the lid to access the loading adjustment. There were other minor improvements to the power supply and regulation during the production of the V-2. The transmitter uses a PTO and multiplier stages to create a tracking exciter that allows the transmitter to stay "in tune" as the frequency is changed. All that is required is for the operator to set the frequency and then "match" the transmitter output to the antenna impedance. Other than the Pi-network, all circuits are automatically tuned as the tuning dial is adjusted. The system used the typical Collins coil-slug rack carriers and full permeability tuning is used throughout the oscillator and multiplier stages. The frequency readout is Collins-accurate.

Most 32-V transmitters do require a bit of work on the "band-in-use" slide rule dial as the illumination (using the ten #328 lamps) is problematic. Also, usually the white plastic backing of the slide rule dial needs to be replaced for first-class appearance. A built-in sidetone oscillator is provided in the CW mode and a PTT function is included for AM. The transmitter is stoutly built with lots of "iron" and weighs in at over 100 lbs.

The PA tube is a Raytheon 4D32 and the 32V allows selectable plate voltage - either +600 or +700vdc -  the lower voltage allowing the 4D32 to run at the manufacturer's specifications for continuous duty and also allowed for reduced output power for driving other devices. The 4D32 tube itself is notorious for developing gassy conditions so be sure to stock several spares. The modulator tubes are "easy-to-obtain" 807s. The power output is generally around 100 watts if +700vdc plate voltage is used and about 65 watts output if +600vdc plate voltage is used. If the +600vdc plate voltage is used, then the Modulator bias will have to be adjusted lower to 50mA and the transmitter has to be loaded to around 180mA of plate current. On +700vdc plate voltage, plate current on AM phone is about 225mA and Modulator bias is 55mA.

If the 32V-2 is conservatively operated per the instruction manual, it is virtually indestructible. A really fine transmitter that is easy to use, reliable, ample power capabilities and allows high quality audio in the AM mode and a very stable CW mode. The 32V-2 was replaced by the 32V-3 in 1952.

32V-2 NOTES: The 32V-2 transmitters used five fixed-value mica capacitors in the Pi-L Network. These mica capacitors were rated at 2500wvdc. It seems to be common for one or more the three capacitors used in the Loading section of the network to fail in the "open" mode. The probable cause is loading the transmitter at full power "key down" while crossing the switching points in the ANT LOADING control. As the loading air variable is rotated, each turn of the ANT LOADING results in a change in the switch position for the fixed-value capacitors that are in parallel. The fixed-value capacitors are only used in position 1, 2 and 3 of the ANT LOADING so generally the failures only occur on either 80M or 40M operation. Though the manual doesn't specifically address this issue, the instructions tell the user to set the ANT LOADING while the transmitter is in the TUNE mode, thus reducing the output power within the network. Switching transients are probably causing the failures, especially if the transmitter loading is adjusted past a switch point in the AM mode (or CW key down) at full power. Follow the manual instructions and adjust the ANT LOADING at the TUNE level so the final, full power "tweaking" only requires minimal adjustment.

The 32V-2 is difficult to work because of the physical layout of the individual chassis that make up complete transmitter. At the rear of the transmitter is the power supply which is built on its own chassis. On the right side is the speech amplifier and modulator, again, built on its own chassis. On the left is the PA and the antenna matching network above and the multiplier section below. In the center is the PTO. The transmitter is essentially built on several chassis that are mounted to form a "U" around the PTO at the center. Some of the chassis sections are somewhat easy to access for repair, like the power supply. Others are more difficult, like the multiplier section. If you have to do any serious rework, some disassembly will be necessary. Add to this, the fact that the 32V-2 weighs around 90 pounds out of the cabinet which makes even the smallest rework a real task.

 

National Company, Inc.  - HRO-60R

Introduced in 1952, the HRO-60 was the last of the evolution of tube-type HRO receivers from National. The power supply is built-in but, to the last, National retained plug-in coil assemblies and the famous micrometer dial (it wouldn't have been an HRO otherwise.) The HRO-60 is double conversion above 7MC, has two RF amplifiers, three IF amplifiers and P/P audio output using 6V6s - 18 tubes in all. The selling price was high at $480 but by production's end, in the early sixties, the price had escalated to nearly $750! Coil assemblies were available for frequency coverage from 50-430KC, 480KC-35MC and 50-54MC. The linear dial uses removable plastic scales that are mounted to a rotatable drum for single band-in-use readout. Two accessory sockets are provided for the optional NBFM adaptor and optional 100KC-1MC Crystal Calibrator. Shown in the photo is the unusual HRO-60R, a rack mount version that included the MRR-2 table rack and the SC-2 speaker panel featuring storage for extra coil assemblies behind the doors.

Some Ham AM ops consider the HRO-60 receivers inferior in performance when compared to the earlier HRO-50 (single conversion, two IF amps) though this opinion is usually based on the audio response which is more restricted on the HRO-60 due to its increased selectivity. The HRO-60 (and the HRO-50-1) used two "double" IF transformers to increase the passband selectivity and added an extra IF stage of amplification compared to the earlier HRO-50. The HRO-60's increased IF selectivity was necessary due to the crowded band conditions of the fifties. Another issue with the HRO-60 is the alignment instructions contained in the National manuals. Many HRO-60s are incorrectly aligned due to the confusion of at least two different first conversion oscillator frequencies used at various times during production. National published at least two different manuals with different first conversion oscillator frequencies, 1990KC and 2010KC. Also, hand-written in one of my original HRO-60 manuals says "1995kc - per National" which appears to have been an owner notation based on a response to a question to National. Generally, the early version HRO-60s use 2010kc and the later versions use 1990kc. The different conversion frequencies will only affect coil sets B, A and the various A bandspread coils sets since these are the only ones using double conversion. Possibly, a slight tracking error may show up if the improper conversion frequency is used. If the tracking seems off on 20M or 10M, then select the other conversion frequency. Tracking should be very good when everything is correct.  The HRO-60 has tremendous sensitivity with low noise, impressive selectivity (QRM is rarely a problem) and "respectable" audio from the P/P 6V6s. Due to the lack of a true speaker enclosure, all rack mounted HROs sound a little "thin" when used with the SC-2 type of speaker panel.

I've owned this particular HRO-60R twice. The first time was in 1990 when I purchased it from a ham in New York state. It was shipped to Nevada and I set-up the HRO-60R to run with a Johnson 500 I had at the time. After a couple of years, I traded the HRO-60R to NU6AM for a really nice National FBX receiver with the band spread coil sets. Sometime later, NU6AM traded it to K6DGH who in turn sold it to KG6YV. All of the trading and selling took place over a period of several years. Around 2003, I asked NU6AM if he knew the whereabouts of the HRO-60R. Jim told me that as far as he knew Greg, KG6YV, still had it. A telephone call to Greg set up the deal and a trip down to California was made for the pick up. I couldn't believe that after ten-plus years absence, I was able to find my old receiver so close by and was able to purchase it back. I now use the HRO-60R as the station receiver with the Johnson Desk KW.

If you want a good laugh and happen to have some older issues of Electric Radio magazine, check out the cover of ER issue #27 - July 1991 - for a photo of this HRO-60R shown above along with your's truly, WA7YBS. If you don't have issue #27 and still want a good laugh, CLICK on:  ER Cover Boy

 

National Company, Inc.  -  NC-183D

National introduced this style of receiver with the 1947 models NC-173 and NC-183. Both were single conversion receivers with the NC-183 offering double pre-selection. By the early fifties, improvements in tube types available and circuit design improvements resulted an updated version of the NC-183, the NC-183D.. The new version was produced from 1952 up to about 1958. Selling for around $370, the NC-183D was an expensive receiver but it did provide the owner with excellent performance that included fabulous audio reproduction. Frequency coverage was from .54mc up to 30mc and additional tuning of 47mc to 55mc for 6M amateur band coverage. Double preselection on all bands and dual conversion on bands A, B and C (the highest frequency coverage) was employed with the IF frequencies being 1720kc and 455kc for dual conversion and 455kc for single conversion. The P-P audio output was supplied by a pair of 6V6 tubes providing about 8 watts of low-distortion, high-quality audio power (11 watts maximum available.) An 8 Z ohm and 500 Z ohm audio outputs were provided. Band spread was provided and featured calibrated scales for 80M, 40M, 20M, 15M, 10M and 6M along with a 0 to 200 logging scale. A six-position Crystal Filter allowed for a wide range of adjustability to the received bandwidth. The three stages of IF amplification utilized pairs of IF transformers with the output of the first transformer coupled to the input of the second transformer to form a tertiary coupling for better selectivity. This IF system was also employed in the HRO-50-1 and HRO-60 to provide the steep bandwidth skirts necessary for good selectivity - something that was essential to cope with the congested ham bands of the fifties and sixties. The receiver used 17 tubes which included an 0B2 voltage regulator. The dial accuracy is very good given that it's an analog dial with limited resolution. Either using received "marker" frequencies or an external crystal calibrator will be helpful in setting reasonable dial accuracy for the ham bandspread tuning. An accessory socket was provided for either an optional NBFM adapter or for the optional National Select-O-Jet (not both, and not for a plug-in Crystal Calibrator.) The Select-O-Jet was connected to the NC-183D accessory socket via a cable and plug from the Select-O-Jet.

The NC-183D is a popular receiver with the vintage AM ham users, primarily because of its very high quality audio reproduction. The receiver was originally supplied with a 10" PM speaker in a matching housing but, if a better speaker system is, the NC-183D can produce fabulous audio reproduction on AM signals. Lots of bass is available and the IF bandwidth is sufficient for fairly wideband audio reproduction. The NC-183D is also sensitive enough and provides adequate selectivity to deal with most reception issues.

In the cosmetic department, the dark silver smooth finish paint always seems to take "hits" from just about anything setting on top of or next to the receiver cabinet. It's difficult to find a NC-183D in mint cosmetic shape. Fortunately, the nomenclature is stamped into the metal so a repaint is possible although only automobile-quality paint that is "custom matched" to the original should be used in any repaint. Often, if the receiver has decent cosmetics, a good "touch-up" is all that's necessary to get a NC-183D looking very presentable.

Many original-condition NC-183D receivers will have a variety of operational problems nowadays generally due to poor storage, hamster rework in the form of unnecessary modifications in addition to some leaky capacitors that can potentially cause heat-related failure of the power transformer if the receiver is operated for long-hours without a proper rebuild. A full rebuild and complete alignment is normally required to obtain the "top performance" that the NC-183D is capable of providing. If you're planning a rebuild, there are 19 molded tubular capacitors to replace but, luckily, a large number of the .01uf capacitors are ceramic disks that won't require replacement. There are 5 electrolytic capacitors that will need replacement. All components are easy to access. Check the carbon resistors for being out-of-tolerance since any leaky bypass capacitors can easily over-heat associated load resistors. Many of the 470K resistors are in parallel with other components in the circuit and will not measure their actual value "in the circuit" and will need one lead "lifted" for accurate measurement. Replace any tubes that don't meet minimum acceptable transconductance. Finish with a complete IF and RF tracking alignment and your NC-183D should become an easy-to-use station receiver that provides excellent sensitivity, acceptable selectivity and very high-quality audio reproduction.

 

E. F. Johnson Company - Viking Navigator
 

The E. F. Johnson Company has been in business since the 1920s and is still active in the component business. During the post-WWII period up to about 1974, Johnson was a major builder of ham transmitters, ham accessories and other communications equipment. The Viking Navigator was introduced in 1957 and was available for about four years. It could be purchased as either a kit or fully assembled. The transmitter-exciter is only 40 watts input power with a little over 25 watts of output power on CW only. Coverage is 160 meters through 10 meters. The PA tube is a 6146 with about 400vdc on the plate.

 
The Navigator featured a fairly standard Johnson VFO, although regulation is somewhat different than their standard VFO as found on the Ranger, for example. Also, a keyer tube is used which provides adjustability of the CW keyed waveform shape. The keyer circuit is also quite different from the Ranger. The "Iron Vane" meter is a source of many problems and its accuracy is always in question. The slide switch that selects Grid or Plate current is also somewhat problematic. Many times, Navigators are found with these two parts replaced. A great QRP CW transmitter that is very small and light weight. Original selling price was $199.50 factory-wired and $149.50 as a kit. Only 840 Navigator transmitters were produced. The Navigator was donated to the museum by K6QY.
 

Photo left shows the Navigator as it was originally with the stock iron vane meter.

Just How Bad is the Original Navigator Meter? - Absolutely Awful. When operating a Navigator as a CW QRP transmitter, the "Iron Vane" meter is constantly "banging" against the zero-stop. Sooner or later, this must have resulted in the meter needle breaking off and ruining the meter. Also, switching transients sometimes caused the coil to "open." That's probably why nowadays so many Navigators have replacement meters. It's very easy to install a jumper across an original meter's terminals to protect the meter and then use an external watt meter to load up the transmitter. A defective original Navigator meter will be next to impossible to replace so this easy protection assures a functional original meter will survive indefinitely (well,...maybe.)

I can't stress the point strongly enough that the original Johnson Navigator "iron vane" meter is a real "piece of junk" and is not really repairable if a problem develops in an original unit (who'd want to fix it anyway.) The plastic cover is glued all around the perimeter of the meter scale backing plate and any attempt to cut away the glue cracks or breaks the plastic cover. Apparently, if a problem developed in the meter, Johnson wanted you to replace the entire meter instead of repairing it. That might have been okay in the late 1950s but now, 50+ years later, I don't think Johnson still stocks Navigator meters. Johnson's decision to install a $2 meter into a $200 (factory-wired price) transmitter was certainly profit-motivated. However, it is possible to fit a Johnson Ranger meter into the Navigator and with some minor adjustments to the shunt(s) it becomes an accurate and useable instrument (which the original Navigator meter never was.) Here's how it's accomplished (after you've found a Viking Ranger meter, of course.

Installing a Viking Ranger Meter into the Navigator - In 2016 I got the chance to actually do something about the original "El Cheap-o" meter used in the Navigator. I was able to obtain a Viking Ranger meter from a junk Ranger that was being "parted out." I tested the meter, which was in very nice cosmetic condition, to see if it was usable electrically. The Ranger meter is a ~5mA FS unit that is a d'Arsonval rotating-coil meter. This design is far more accurate than the crude "iron vane" meter that relies on magnetic attraction of a "vane" to move the meter pointer. A quick test is to just measure the DCR of the meter coil. In this case it measured ~20 ohms. A more accurate test is to actually measure how much current is required for a full scale indication. An adjustable low-level dc voltage is connected in series with a 1K ohm resistor, a current meter and the meter under test. The dc voltage is adjusted until the meter under test shows a full scale indication. The current meter will now show how much current is needed for full scale deflection on the meter under test. In this case, it is 4.5mA. Linearity can also be checked at half-scale, in this meter it was 2.2mA. 

Something Interesting with the Original Meter - I hadn't operated the Viking Navigator since I had moved from Virginia City in 2012. The Navigator had been in storage in the upstairs lab which is a stable environment with no extremes of any sort. In my research before actually performing the Ranger meter installation, I thought I'd test the original iron-vane meter. A measurement of the coil showed no continuity at the terminals. I had run into this problem once before when I first got the Navigator. At that time, loosening the terminal nuts and retightening them got the meter functional. This time, no amount of loosening and tightening helped. The meter coil was disconnected from the terminals. There is no repairing the original meter. It can't be taken apart since the plastic cover is glued to the back and any stress on the plastic results in cracks. Better to leave the original meter in good cosmetic condition albeit non-functional since I was planning on installing the Ranger meter anyway.  >>>

The Installation Plan - One can't just remove the old Navigator meter and bolt-in the Ranger meter. These are two different types of meters that have different FS indications and FS current requirements. This will require re-calculating the shunt values needed for the Ranger meter to accurately read PA grid current and PA plate current in the Navigator.

Additionally, the Ranger meter isn't exactly a perfect replacement fit. The original Navigator meter requires a 2" diameter hole while the Ranger meter requires a 2.187" hole. The original Navigator meter was mounted using a bracket that attached to the back of the meter and pushed against the back of the front panel to hold the meter secure. The Ranger meter mounts conventionally using four studs that use 4-40 nuts and washers to secure the meter to the panel. This means some modification to the front panel is necessary. Fortunately, if for some reason the original Navigator meter was to be re-installed, the modified larger clearance hole and the four mounting holes are covered up by the overall size of the original meter.

Originality versus Cool Functionality - Anyone who reads any of my articles knows I'm a serious advocate for strict originality. How could I actually want to modify a rarely encountered transmitter to the point where I'd actually be "cutting and hacking?" It seemed unthinkable! However, that's just how BAD the original Navigator meter is. I would think that the E. F. Johnson decision to use the iron-vane meter was based on keeping costs low so the Navigator would be reasonably priced (it really wasn't.) If Johnson could have put another $15 to $20 into the cost, they would have used the Ranger meter. The Ranger meter is a genuine "Johnson" part and even has the Viking head on the scale. Additionally, it is an illuminated meter (the original iron vane meter isn't.) So, my argument for performing this modification is "Johnson would have liked to have built the Navigator this way but it would have cost a lot more and sales would have been even less than they were!"  Maybe Johnson could have offered this version as the "Deluxe Navigator."  

Before Cutting the Sheet Metal,...Test - Always a good idea. Make sure your modifications are actually going to function correctly. In this case, the modification was to the shunts used in the Navigator. We don't really need to know what the original iron vane meter required since it was now non-functional. So, if your Navigator has a bad original meter or some sort of replacement meter and you want to install a Viking Ranger meter, you'll need to calculate the shunts. Normally, you can use the formula of R shunt=R coil/n-1 where n=change in scaling. In the case of the Ip our FS is 200mA and the FS meter movement is 5mA so n=200/5 or 40, so n-1=39. The formula then is R shunt=20/39 or ~0.5ohms. An accurate digital current and ohm meter that will read low value ohms and milliamperes accurately helps in final accuracy of the shunt calculation and resistor selection.

I did a quick test for the grid current using 10mA FS with R shunt=20/4 or ~ 5 ohms. I installed a 5.1 ohm resistor for the grid current shunt. Although the original meter didn't require a shunt, the Meter switch has an extra unused pin (pin 9) that can be used for a grid current shunt resistor connection into the circuit.

During testing I wanted to double-check the accuracy of the Ranger meter and the shunts. I did this by using an accurate current meter installed directly into the grid circuit. I adjusted the Navigator to show 4mA of grid current. I then connected the Ranger meter which showed 2.5mA. A slightly higher shunt resistance was needed so I installed a 6.8 ohm resistor and this then allowed the Ranger meter to show 4mA. I did the same with the plate current shunt and ended up with 1.0 ohm, 1.2 ohm and 1.5 ohm resistors in parallel, or about 0.27 ohms, for an accurately reading plate current meter.

As to why the actual shunt values were slightly different from the calculated values was probably due to the meter I used to measure the Ranger meter coil resistance. I really needed a digital meter that was capable of measuring "low ohms" accurately which I didn't have. Also, the actual FS current for the meter was 4.5mA and I used 5.0mA in the calculations. With these two changes my calculations would have probably been accurate. As it was, I got close and then "trimmed" the values to have the Ranger meter read accurately by comparison with a known accurate current meter.  >>>

Sheet Metal Work - Now that we had the Ranger meter working with the Navigator we had to actually modify the front panel so that the Ranger meter would fit and could be mounted. Trying to do sheet metal work with the panel mounted to the chassis will result in difficulty getting an accurate fit. It's better to entirely remove the front panel so you can rework the meter hole neatly and drill the four mounting holes precisely. There are many ways to enlarge the meter hole but since we were only removing 3/32" around the perimeter of the hole, I carefully used a nibbling tool and then finished with a fine round file. The mounting holes were drilled. See photo below for the appearance of this "hand fitting" job.

Connecting the Meter - Since Johnson used their "Edison Inductor" chokes for the meter connections, a tie-point was mounted on the bracket in back of the original meter. I relocated this tie-point to the screw and nut that mounted the slide-switch bracket. The chokes were connected to the meter terminals and short jumper wires connected the bypass capacitors and the slide-switch. See photo right. Note the long studs for the meter connections. These long studs were needed because originally, in the Ranger, there was a metal cover-shield that entirely enclosed the meter and these studs had to be insulated and protrude through the back of the shield-cover. Unfortunately, the shield-cover wasn't included with the Ranger meter purchase.

Meter Illumination - The dial lamps are all connected via chokes so the meter lamp also needed to be bypassed with a capacitor and connected with a choke. I wound a new "Edison Inductor" choke for the connection. The lamp socket would have originally "snapped into" a hole in the back of the metal meter cover (that wasn't included in the Ranger meter purchase.) I was looking around the shop for something that would work when I noticed a dial brace on a "junker" NC-200 receiver. It looked about the right size for a chassis-mounted lamp bracket. Luckily, there was an existing hole in the Navigator chassis that allowed mounting the bracket in just the right position to allow a near-perfect entry of the lamp socket and bulb into the meter illumination hole. I mounted a tie-point to an upper meter mounting stud to hold the bypass capacitor and inductor. Illumination was provided by a #47 lamp. See photo right. NOTE: I'll re-do the meter illumination correctly when I locate an original Ranger meter cover-shield.

Keying Adjustment - R-9 adjusts the keying circuit to produce a "shaped" wave envelope that has a somewhat slow start and finish to the pattern. This reduces "clicks" that are sometimes heard with CW transmitters. The procedure is to adjust R-9 for full "on" keying and then adjust in the opposite direction until the keying just turns "off." Then continue slightly past the turn "off" position. A little vague. I adjusted by listening to the keying with the Navigator on the dummy load and listening on a R-390A receiver. I found the best sounding keying was actually quite a bit farther into the pot rotation rather than just "slightly." I found the keying tended to "bloop" if R-9 wasn't adjusted quite a bit past the "off" position.

Operation - Testing into a dummy load plus a Drake W-4 wattmeter showed that I could load the Navigator to about 25 watts maximum output power. The Navigator was rated at 40 watts input power so the 25 watts equates to about 62.5% efficiency which is about right for Class C PA operation at the plate voltage the 6146 is provided with (around +400vdc.) On CW, 25 watts output power is sufficient for communications provided a decent antenna is used. I used my regular ham antenna, a 135' center-fed inverted-vee fed with 94' of ladder line. When used on 40M this antenna becomes "two half-waves in-phase" and begins to exhibit a little gain - not much,...maybe 0.5db over a regular dipole. I selected 40M so I could do my test QSO during the day. Although there isn't a tremendous amount of activity on 40M CW during the day, there isn't any QRM either.

Ultimately, I will probably use the Navigator as the exciter to drive the KOWL Gates AM-BC transmitter, the BC-250L. This transmitter originally used a crystal-controlled oscillator on 1490kc. It would be easy to bypass the oscillator and run the Navigator directly into the driver stage of the transmitter. This would allow some frequency mobility on the 160M or 80M bands. 

Photo left shows the "Deluxe" Navigator with the Johnson Viking Ranger meter installed. The top scale is 0 to 200mA and used for plate current. The 0-5-10 middle scale is used for 0 to 10mA grid current.

 

E. F. Johnson Company -  Viking Desk Kilowatt, Viking Ranger, Viking KW Match Box

The Viking Desk KW was introduced in 1955 and was available up to around 1964. The "Desk" is a high power RF amplifier with a high power audio modulator, power supplies and all of the control equipment built into a fairly compact "pedestal." The Desk KW features continuous tuning from 3.5 to 30mc. The PA operates Class C and has two output levels, low power for tuning up or operation at 250 watts carrier output or high power for 1KW input power. Plate voltage is either 1300vdc or 2600vdc depending on the output power selection. Originally, 872 MV rectifiers were used for the Plate supply but many amateurs have replaced these with 4B32 Xenon rectifiers or with Solid State rectifiers. An external relay (operated by the exciter) must be used with the Desk KW for linear operation for SSB to allow switching between "Blocking Bias" and "Operating Bias." The PA requires 30 watts of drive for full output and the modulator requires 15W for full audio drive on AM. The PA tubes are a pair of 4-250A tubes (4-400 on later Desks) modulated by a pair of 810 tubes. The entire unit is on guides and rollers and is easily accessed for testing or adjustments. The desk itself was a $123.50 option that could be bolted to the side of the pedestal for complete operating station desk with room for the exciter and the station receiver. The Desk KW sold $1595 without the desk. The Desk KW shown is number 280 of the 402 built.

The Viking Ranger was a 75 watt CW or 65 watt AM exciter-transmitter that covered 160M to 10M and had a built-in VFO that was very stable. The audio section featured a special modulation transformer with a winding that was used for negative feedback resulting in excellent quality audio. The PA tube is a single 6146 and the modulator tubes are a pair of 1614 tubes. The Ranger had all of the outputs accessible to interface with the Desk KW for sufficient drive for full output from the Desk KW. Generally a small attenuator is inserted between the Ranger RF output and the Desk KW input to allow better adjustment of the Ranger's drive and output circuits. Rangers were very popular as a stand-alone transmitter also, especially for Novices since the power limit then was 75W on CW only, crystal control (you got to use the VFO after you up-graded your license.) Still today, the Ranger is a popular transmitter for vintage AM because of its excellent audio and "bullet-proof" construction. Over 14,000 Rangers were built. They were available as either a kit or fully assembled. Prices were $293 assembled or $214.50 as a kit. The later version was designated as the Ranger II and featured different modulator tubes, a two-tone gray paint job and dropping the 11M coverage in favor of 6M coverage.

The Viking Match Box was a heavy duty, balanced antenna coupler that was link coupled, used bandswitching and had two split-stator variable capacitors that allowed matching various kinds of antenna loads to a transmitter. The Match Box was specifically designed for balanced antennas but could also match coax fed loads or end fed wires. The SWR bridge required an external Directional Coupler to function but the Match Box was available without the SWR bridge option in which case there is no meter installed. A built-in antenna relay is included inside the box with access via an external terminal strip mounted on the rear of the unit.

The Viking Desk KW shown was partially disassembled and was going to be "parted out" by the University of Nevada (in 1997.) A friend of mine that worked at UNR saw the Desk KW (disassembled) in the hall on the second floor of the Electronics Building. His phone call to me was something like,... "you interested in a Johnson Desk KW? Well you better get over here, they're throwing one away." When I got to the Electronics Building, I found the Desk KW apart and looking like it was destined for destruction. I asked around and finally found that the Wolf Pack Ham Club had gotten the Desk as a donation and they weren't sure what to do with it since they couldn't move it to the third floor where their ham club station was. I made a deal with them of cash for some equipment they wanted to buy and then the Desk KW was on its way to Virginia City. The KW Matchbox was included in the deal. I rebuilt the Desk KW and it is now fully operational and usually on the air on the Saturday Morning West Coast AM 75M Net (8AM Pacific Time, 3870 KC.) The Viking Ranger was the XYLs Novice transmitter back in 1975. We've always kept it in operational condition. Several years ago I replaced all of the aging capacitors. Other than increasing the wattage rating of the regulator resistor (but not changing its proper location in the VFO) no mods are installed  - Rangers sound very nice with stock audio.

Inside the Viking Desk KW - The Desk KW is the type of transmitter that is going to require maintenance from time to time. The most common annoyances will be located in the Potter-Brumfield relays since their contacts always seem to need attention after a year or two of operation. It's pretty easy to access the relays since they are located in the front of the two-tier chassis. Clean the contacts with 400 grit Alu-Ox paper and do the final clean with De-Oxit on a piece of paper pulled through the contacts. These contacts are always pitted so don't worry about the 400 grit paper damaging the contacts - they are already damaged.

One of the main problems with the Desk KW is that it was wired with solid conductor wire which has a real tendency to break when moved. Of course, Johnson thought you'd never be moving the harness around but you have to when going through the transmitter. Keep an eye on the wires while doing any rework as you're sure to break at least one wire during the process.

The four fans used in the Desk KW are also problems. The two main fans "push and pull" the air through the Desk chassis to keep everything cool. These open frame fans don't last forever and many have been replaced over the years. There are exact duplicates of the fan motors still available and many suppliers stock them. Reuse the original fan blade and be sure that you have the lower fan pushing air in and the upper fan blowing air out. The originals should be serviced every year or so. Oil the felts by saturation with light machine oil.

If you're using a Ranger to drive the Desk KW, you'll be plugging the Ranger into the AC socket that is provided at the rear of the Desk chassis. If you have the Ranger's AC plug oriented one way, the relay drive to the Desk works. Oriented the other way, the Desk relays won't work. Once you've determined which way is correct, paint the upper part of the Ranger's AC plug with red paint. That way, in the future, you'll always know which way to plug-in the Ranger.   >>>
>>> I had to replace the two toggle switches on this Desk KW. The originals are rated at 3A at 125vac - a pretty hefty switch - but they became intermittent after 50 years of use. I replaced them with 10A 125vac toggle switches. For the AC power switch (SPST) this is no problem since there's plenty of room. For the meter selection switch though I had to modify the switch terminals by cutting them down as low as possible. Then I drilled a 1/16" hole in each shortened terminals for the wires to mount into. Also, the switch has to be mounted as far forward as possible. Because the switch is in front of the meter terminal board and both are located in the shielded meter box, there isn't much room for a large toggle switch but with slight modification, it all fits together.

The Desk KW chassis rolls out but only so far until you are going to have to support the front. I use a $12 dolly that you can find at Home Depot or many other hardware stores. The dolly is placed under the Desk chassis and as you pull the chassis out you move the dolly more to the center of the chassis until the chassis is entirely out of the pedestal. Then you'll have a way to roll the chassis around for easy access to all areas. The chassis weighs close to 200 lbs with all of the iron installed, so the dolly helps a lot. When re-installing the chassis into the pedestal, I use a lever (a five foot long piece of 3/4" pipe) to lift each back edge of the chassis into the pedestal. Once both edges are in, then it's easy to push the chassis back in on the internal rollers.

I use 6156 tubes in the final PA because these RCA versions of the Eimac 4-250A are usually cheaper but have the same specs. The only difference is the 6156 doesn't have the metal base shroud to direct air flow around the tube. Since we only run the Desk KW in the "Tune Mode" it is never really running more than at just "an idle" and therefore the 6156s work fine. I also don't use the original 872 MV rectifier tubes but use 4B32 Xenon rectifier tubes.


photo above: Output Network with over-sized roller inductor and large air variable capacitor. Photo right: The finals - a pair of 6156 tubes which are the RCA equivalents of Eimac 4-250A tubes


photo above: The modulator section showing the pair of 810 tubes and the huge modulation transformer.

 

Central Electronics, Inc. -  100V Multiphase Transmitter

Central Electronics was founded by Wesley Schum W9DYV in the early 1950s. Their main products were phasing-type SSB transmitters-exciters, although some SSB-oriented receiving devices and monitoring equipment also were produced. Around 1958, Zenith Radio Corporation acquired Central Electronics. At about the same time, CE introduced the 100V transmitter. The design was by Schum and engineer, Joe Batchelor. Initially, several minor problems caused delays in delivery of the first 100Vs produced. Dealers were sent the first 100Vs to help promote the transmitter by actually using them on the air. Selling price was around $800. Eventually, around 1500 100V transmitters were produced before the 200V was introduced in 1961. About the same time, Zenith began to institute cost-cutting measures and eventually, in 1962, closed down Central Electronics due to low profits for Zenith.

The CE 100V design uses a phasing-type of approach to sideband suppression. In addition to USB and LSB, DSB-SC, DSB-AM, PM, FSK and CW modes can be selected. Unique to the CE 100V is the broadband output section that allows the operator to select a frequency and begin transmitting - no antenna loading or tuning is required. The broadband circuitry does require that a low SWR be presented to the transmitter output and an illuminated indicator warns the user if the SWR is too high. Most of the controls are located under the two doors on the front panel. These were considered "set and forget" type controls. A two-speed VFO tuning control allows very fine adjustment of the frequency. A monitoring CRT was provided and displayed a trapezoid pattern when the transmitter was properly adjusted. Typical output power was 100W PEP although the output was continuously adjustable down to 10W.

Today, the CE-100V is still a popular transmitter because of its versatility, excellent audio capabilities and incredibly ""good looks." The 100V shown above still needs to be restored. While it does function, like all 100Vs that haven't been restored, it needs to be "gone thru." When purchased, the audio limiter module, the audio filter module and a relay cover were missing. These parts have since been found so the transmitter is now complete. Also, the power supply rectifiers had been "solid-stated." This mod was removed and the transmitter put back to original vacuum tube rectifiers. All that is left to do (cosmetically) is to acquire a better condition kilocycle dial and meter scale. Also, the cabinet is in very poor condition and needs to be repainted. The original color is grayish-brown (gray with a lot of brown mixed in) wrinkle finish. Unfortunately, all 100V transmitters were wired in a haphazard (sloppy) manner with virtually no neatness to any layout. Although they work great, on the underside, they don't look like they would. Even when restored, the underside will still look like it was wired by a "hamster."

 

Eldico Electronics  -  SSB-100-F

Eldico Electronics was formed by Paul Wright W9OHM in the early 1950s. The company produced mostly ham transmitters. Around 1957, Eldico was purchased by Dynamics Corporation of America and shortly thereafter sold to Radio Engineering Labs (REL) of Long Island City, NY.

Eldico is mainly known for the Collins S-line "clones" they built in the late-1950s. These initially were part of a military second-source contract between Eldico and the military, however Eldico then decided to also sell the "clones" directly to the general public. That Eldico was using the S-line clones to apparently compete with Collins upset that company, who then pressured Eldico to stop production of the clones. However many examples were sold and they are still relatively easy to find.

The SSB-100-F came out in 1957. It was a balanced modulator-crystal filter ssb supression type transmitter that used 5894 in the final PA. The transmitter covered 80M thru 10M with 10M covered in three individual bands. 11M was also covered since the SSB-100-F was a pre-CB era rig. The circuit uses 22 tubes including a 1CP1 1" diameter CRT that is used to provide a trapezoid pattern for monitoring transmitted audio quality. The SSB-100F was rated at 100 watts PEP input power in SSB, 50 watts input power on CW and 25 watts SSB-AM. Only one sideband could be transmitted in the AM mode. Carrier was reinserted post-filter to accomplish a SSB-AM signal. VOX or Manual operation was provided but not PTT.

Not too many SSB-100-F were produced. Priced at $795, it's not surprising that sales were slow. Estimates are around 300 to 500 units were produced. The SSB-100-F shown is serial number 0067. I also have a "parts set" SSB-100F with the serial number 0079. Eldico also produced a SSB-100MIL version that provided 12 crystal-controlled selectable channels besides a VFO. Eldico also produced a linear amplifier, the SSB-1000.



Eldico SSB-100F  SN: 0067  ca: 1958
 

 

Shown above is 75A-4 sn875 (with all up-grades.) I purchased this 75A-4 in April 1970 and it has been "paired" with a matching KWS-1 (sn616) transmitter since December, 1970.
 

Collins Radio Co.  -  75A-4 

Considered by many radio amateurs to be the finest "ham bands only" tube-type receiver ever produced. The Collins 75A-4 was introduced in 1955 and manufactured up to about 1958 or so, with around 6000 total production. The 22 tube circuit featured a 3.1 kc mechanical filter and a product detector, making the 75A-4 ready for SSB - but it could also copy AM quite well since a separate AM envelope detector was also provided. For better AM copy an optional 6.0 kc mechanical filter could be purchased or, for CW, an 800Hz filter was available. Later, other filter frequencies were offered, e.g., 500 cycle for CW, 2.1 kc for SSB, plus others. Up to three mechanical filters could be installed, providing optimum selectivity for CW, SSB or AM. Frequency readout was "Collins accurate" and sensitivity was competitive. Audio was fairly good because of the envelope detector used on AM but the 6.0kc is necessary for adequate bandwidth unless only one sideband is listened to (on AM.) The 4:1 vernier knob was an early option that allowed for very smooth tuning and the later models had it installed "from the factory."  Earlier models had a fairly high hum level and problems with the AVC. Collins installed up-grades rather early in production to correct these problems, although there were many upgrades from Collins through most of the 75A-4 production. Collectors usually favor the later serial numbers (higher than 4000) since all up-grades were in place by that time. However, Collins offered service bulletins and up-grade kits which many owners installed themselves, so serial numbers alone do not tell you the performance capabilities of a particular 75A-4.

In use, the 75A-4 is an excellent performer. Its ability to eliminate adjacent frequency QRM is amazing. Using the Passband Tuning, an offending signal can be "dropped off" of the edge of one sideband while another offending signal on the opposite sideband can be eliminated using the Rejection Tuning. This ability to effectively eliminate two interfering signals simultaneously is impressive and makes the 75A-4 a valuable addition to a vintage AM station, even though the receiver is generally considered a SSB/CW receiver.

Collins Radio Co.  -  KWS-1

The KWS-1 was an incredible transmitter when it was introduced in 1955. At a time when AM dominated the voice mode of communications, Collins introduced a high-power SSB transmitter that was so expensive, nobody could afford it - $2100. Everything about the KWS-1 is first-class. The construction was military-grade, the components first-rate and the design was "cutting edge" for 1955. Total production was around 1600 transmitters.

The KWS-1 is capable of 1KW PEP input power SSB transmission utilizing a 3.1kc mechanical filter and balanced diode-ring modulator to create the selectable USB or LSB signal with suppressed carrier. Further mixing in various stages converts the signal to the proper output frequency. It is then routed into the Class AB-1 Linear Amplifier comprised of two 4X150 external anode, air-cooled tubes run in parallel (now 4CX250Bs.) Plate voltage is 2KV. The power output of a properly operating KWS-1 is around 625W DC. In the AM mode, the carrier is reinserted but the signal is still kept in a single-side band mode. Operating a KWS-1 in the AM mode will usually foment some negative comments from the "BC-Audio Crowd" but, unless mentioned, many "more tolerant AMers" never notice that only one sideband is being transmitted. Since AM is a 100% duty-cycle mode, the power has to be reduced to about 150W of carrier output. In the CW mode a full 1KW (input power) can be utilized since the duty-cycle is usually around 50%. Due to the 3.1kc mechanical filter, the KWS-1 sounds incredible on SSB today since most hams are used to hearing rather narrow SSB (2.1kc) and generally a QSO will garner positive comments on its SSB audio.

The KWS-1 power supply is contained in the larger floor mount pedestal. Originally, a pair of 866A MV tubes were used as rectifiers but most have been replaced with 3B28 HV rectifiers or some even go SS rectifiers (I use 3B28s.) The regulated screen voltage is adjustable and so is the plate voltage to a certain extent (you can move the connections to different taps on the plate transformer.) The squirrel-cage blower is also mounted in the base of the pedestal. It is fairly noisy (bearings should be lubed every few years and many just need to be replaced) and the air output is routed through a 2" diameter radiator hose (for lack of a better description.) The 2KV plate voltage is run through a cable made from RG-58U and the connector on the RF unit is somewhat problematic in its ability to stay connected. The remaining power is routed through a flexible cable with rectangular Amphenol multi-pin connector. 

I purchased my KWS-1 sn:616 from Al, K6RIM, in December, 1970. Al had purchased the KWS-1 in used condition, in 1960, from Amrad Electronics in Burlingame, California (later called Ham Radio Outlet.) SN 616 has been my main transmitter for many years and has proven to be a super-flexible unit capable of high power SSB and CW with reduced power AM and RTTY communications. The KWS-1 is mostly original with only routine maintenance having been performed over the years. I did have to repair a broken flex connection on one of the roller inductors a few years ago, also a broken wire in the microphone connector. I now use the KWS-1/75A-4 on AM on the Vintage Military Radio Net where it provided a unique type of AM for enthusiasts to hear - one selectable sideband with carrier. The KWS-1/75A-4 have a long association with military MARS stations and, of course, the SSB promotion that involved Art Collins and the Air Force in the mid-fifties. The KWS-1 is certainly one of the best from the "Golden Age of Ham Radio."

OPERATIONAL NOTE: AM on the KWS-1 is not without headaches - mostly in the form of "Critical Audio Reports" from the BC-audio crowd. The KWS-1 will NEVER sound like double-sideband AM and it will NEVER sound like high fidelity AM. No matter how many times you describe the KWS-1's method of generating an AM signal and the fact that it's a "single sideband signal with reinserted carrier" you'll still run into those listeners that expect AM BC-quality audio from anything built by Collins. However, a few things performed during AM set-up can avoid most "Critical Audio Reports" when using the KWS-1. Be sure to run the carrier reinsertion (Carrier Level) so that it results in about one-quarter power as compared to full power output. This is usually about 150 watts of carrier and is usually achieved at about 250mA of PA current. Use an inline watt meter to be sure of the carrier power output. Typical full power output DC on a KWS-1 will be around 625 watts so one-quarter would be around 150 watts. Be sure to run the Audio Gain very low - usually about 1 or so - and never use the ALC - always keep the ALC at full CCW in the AM mode. Be sure to monitor the PA Grid current - it should never move from 0. Any grid current flowing will create distortion. Even a minor fluctuation of the Grid Current meter needle is indicating non-linearity and resulting distortion. Keep the Audio Gain low and avoid excited, over-animated voice levels (if possible.) Following these suggestions will have your KWS-1 producing "its type of AM" about as well as it can. You'll still get "Critical Audio Reports" but that's life in ham radio.

 

References:

1. "Communications Receivers - The Vacuum Tube Era, 1932-1981"  by Raymond S. Moore - Undoubtedly the best reference book on tube-type superheterodyne communications receivers. History of receivers and the companies along with circuit description and photos of each receiver. Four editions have been printed.

2. "Shortwave Receivers Past & Present - Communications Receivers 1942-1997"  by Fred Osterman - Excellent reference book on later communications receivers. Includes many foreign makes. Circuit descriptions, photos, prices. There is a new, expanded edition now available (2016.)

3. QST, Radio News and Shortwave Craft magazines from 1928 up to 1948 - These vintage magazines are excellent sources for contemporary reviews of equipment and pre-production articles by the designers. Advertisments are invaluable for dating and development of the model line.

4. Operator's Instructions, Factory Manuals, Rider's Troubleshooting Manuals - Original manuals are excellent sources for circuit descriptions, design intentions and performance expectations. Many times the same information is included in the appropriate Rider's Troubleshooting Manual.

____________________________________________________________________

Donations to Radio Boulevard - Western Historic Radio Museum's Website

If you enjoy using Radio Boulevard - Western Historic Radio Museum's website as an information resource and have found our photos, our hard to find information or our restoration articles helpful, then please consider a donation to the WHRM website. A small donation will help with the expenses of website operation, which includes research, photographing and composition. WHRM was a real museum that was "Open-to-the-Public" from 1994 to 2012 - eighteen years of operation. WHRM will continue to provide its on-line information source with this website, which has been in operation since 1997.

Please use PayPal for sending a donation by clicking on the "Donate" Button below

________________________________________________

Website Navigation Index

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

Home-Index

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

 THE COLIN B. KENNEDY COMPANY
"RADIO APPARATUS OF QUALITY"
Universal, Intermediate Wave and Short Wave Models History, Restoration and Operation - Lots of Photos

A.H. GREBE & CO., INC.
"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