Western Historic Radio Museum

Commercial and Military Communications Gear

- 1932 to 1959 -
 

Post-WWII Ham Gear
 

 Amateur Radio Receivers
 and
Amateur Radio Transmitters
 

- 1946 to 1957 -
 

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

Mackay Radio & Telegraph Co.  -  Type 105-A
Contractor: Federal Telegraph Company

Mackay Radio & Telegraph Company was founded by Clarence Mackay, son of John W. Mackay, one of the "Big Four of the Comstock" fame here in Virginia City, Nevada. John Mackay initially made his fortune in Comstock silver but he later (1883) moved into telegraphic communications. Mackay, along with J. Gordon Bennett Jr., formed several telegraph communications companies to compete with Jay Gould's Western Union. Postal Telegraph Company (1886) was the best known, along with Commercial Cable Company (1884). Eventually, these companies, along with other Mackay-Bennett telegraph companies, had transoceanic cables across both major oceans. When John Mackay died in 1902, Clarence inherited the businesses. Clarence Mackay saw to the completion of the transpacific cable in 1904. Radio was added to the business end of things in 1925 to provide "radiogram" service to every area of the world. Mackay Radio was mainly interested in maritime communications which went along with the maritime radio-telegraph business. By 1928, ITT had merged with most of Mackay's business interests but the Mackay name continued on for several decades. Today, Mackay Communications is still doing business, located in North Carolina.

Federal Telegraph Company started out in Palo Alto, California mainly dealing in arc transmitters. At one time, Lee DeForest worked for the company but Frederick Kolster was the head engineer for most of FTC's history. FTC bought Brandes and created a division called Kolster Radio Company for selling consumer radios in the mid-twenties. FTC became involved with Mackay Radio in 1926 when Mackay bought a radio station that had belonged to FTC. When Mackay sold his interests to ITT, then Federal Telegraph was contracted to do most of the Mackay Radio work. Federal Telegraph moved to New Jersey in 1931 when it was purchased by ITT. For awhile ITT tried the consumer radio market with Kolster International but it was a short-lived venture. The name of Federal Telegraph Co. was changed to Federal Telephone and Radio Company around 1940.

The Type 105-A is actually a pre-WWII commercial shipboard receiver that dates from sometime after the Federal Telegraph move to New Jersey since the ID tag lists Newark, N.J. as FTC's location. It is a four tube receiver using five-pin cathode-type tubes. It is possible to use type 27 or type 56 tubes and with an increase in the filament voltage, type 76 tubes could also be used. It is possible that this Type 105-A was updated either at the factory or by a professional radio work shop for the cathode type tubes since there are some indications that the original design may have used direct-heated filament type triodes. The frequency coverage is 1500kc down to 15kc in seven tuning ranges. Power is supplied by batteries. Like earlier designs for shipboard receivers, e.g. the IP-501-A, the Mackay 105-A utilizes an LC Antenna tuner ahead of the regenerative detector to increase gain and selectivity. An Antenna Series Condenser switch selects various value capacitors to match the ship antenna to the receiver input and a stepped Tone control provides some relief from static. The panel meter is a dual meter that normally reads filament voltage but B+ voltage can also be monitored by activating a panel switch. The left large tuning knob tunes the Antenna Condenser, the middle large knob controls the Regeneration Condenser and the right large knob tunes the Detector Condenser. The Mackay 105-A is built for shipboard use being physically stout and very heavy. Originally the receiver was panel mounted in one of the Mackay Marine Radio Units that housed the majority of the radio gear for the ship. (See our "Vintage Longwave Receivers" webpage for an in depth article about this receiver.)

Mackay Radio & Telegraph Co. - Type 102-B Frequency Monitor   Shown in the photo to the right is an accessory piece of test-monitoring equipment for shipboard operation, the Type 102-B Frequency Monitor. This device works something like a heterodyne frequency meter. A small antenna would be connected to the binding post terminal on the front panel (top-center.) This antenna can act as a pickup or a radiator depending on the operator's intentions. Internally, the 102-B has a type 76 oscillator feeding a type 6C6 buffer. These stages then capacitively feed the tank circuit of a type 76 broadly tuned RF amplifier whose input grid is connected to the antenna post and whose plate output is capacitively coupled to the telephone jack on the front panel. When it is desired to monitor or test a transmitted signal, the operating frequency can be determined as a heterodyne beating with the internal oscillator heard on 'phones plugged into the phone jack. Since most shipboard transmitters in the thirties operated CW or MCW, the operator could also monitor the transmitted signal for other characteristics or suspected problems. When it was desired to test a receiver, the internal oscillator-buffer of the 102-B emits a small amplitude signal from the small antenna which can be received and beat with the receiver's tuned frequency to determine the actual received frequency. Frequency coverage is from 5.5MC up to 16.5MC. Built by Federal Telegraph Company, the Type102-B is stoutly built into a steel cabinet. The airplane-type dial is not illuminated since the entire device runs on batteries. There is a power cable access hole on the right side of the cabinet. Dates from 1938.

AR-88D ca.1944

Radio Corporation of America  -  AR-88 Series

     includes: AR-88D, AR-88LF, CR-88, CR-91, SC-88, R-320/FRC - also Triple Diversity Receivers DR-89, RDM and OA-58A/FRC 

RCA's greatest communications receiver creation was the AR-88. Designed in 1941 by Lester Fowler and George Blaker, the AR-88 was a 14 tube superheterodyne that covered .54 to 32MC in six tuning ranges and featured incredible sensitivity (even up to 10 meters), excellent stability and high fidelity audio (from a single 6K6.) Most of the production was sent to England, Russia or other Allies during WWII because of Lend-Lease which accounts for the relative scarcity of the early versions of the receiver in the USA. The AR-88 was used extensively in Great Britain during WWII for various purposes. RCA and Radio Marine Corp.of America also used the AR-88 and its variants in their own installations for various purposes. Even the US Military used some of the later AR-88 variations in their installations. Contrary to some published estimates of unbelievably high production levels in excess of 100,000 units, serial number analysis seems to indicate that around 30,000 AR-88 series receivers were built between 1941 and 1953.

Shown in the header photo is the AR-88D from WWII. The first inset photo shows the early version of the CR-91, a receiver that is very similar to the AR-88 but with a frequency coverage of 70kc up to 550kc in the first two bands and then 1.5mc to 30mc in the remaining four bands. The CR-91 uses a different IF frequency of 735kc to allow continuous coverage in the LF and MF spectrum. Additionally, the audio output tube was changed from the 6K6 to a 6V6. The slightly different (wider) IF bandwidths are a product of the higher IF frequency. The CR-91 version was introduced during the last part of WWII with these receivers built at Camden and having the non-adjustable crystal filter phasing and a black wrinkle finish panel. The later CR-91A essentially took the place of the AR-88LF with all manufacturing at the RCA plant in Montreal. The CR-91A was an updated version that has the front panel crystal filter phasing control and a smooth gray finish on the front panel. Most early CR-91 receivers were in cabinets and were probably used for surveillance or LF/MF communications onboard ships (some CR-91 manuals warn about excessive LO radiation on the antenna if the A2-G link is removed.) Shown in the second inset photo is the 1947 CR-88A. These receivers were generally for the later versions of the DR-89 and RDM Triple Diversity Receivers but sometimes they are found as individual receivers that were used for a multitude of purposes. This example of the CR-88A is installed in a matching RCA cabinet. 

For the ultimate information source on the AR-88, including more history, the triple-diversity receivers, serial number analysis, how to do sweep IF alignment, restoration hints and performance details go to our web article "RCA's Amazing AR-88 Receivers" - Link below in the Navigation Index.

Canadian Marconi Company  -  CSR-5

The Canadian Marconi Company was contracted to build a high quality receiver for the Royal Canadian Navy in early 1943. Most CSR-5 receivers were built in 1944 and were part of the first delivery of  receivers to the RCN. Sometime in 1944, the CSR-5A was introduced. The CSR-5 was used for several purposes, even though its primary intended use was aboard ship. Shipboard use required extensive shielding in the receiver to allow its operation along side other equipment without causing interference or radiating the LO from the antenna. Apparently, the RCN found other uses for the CSR-5 and most were not installed onboard ships until the early 1950s. The receiver's frequency coverage was in two sections, 75kc to 530kc and 1.5mc to 30mc, in six bands. Each scale on the large illuminated dial was color coded. The CSR-5A replaced some of the 6SK7 tubes with 6SG7 tubes (in the RF and IF) as the major change, however there were many other minor changes in the cabinet style, power connector orientation, dial scales, etc. Many of the earlier CSR-5 receivers were retrofitted with the 6SG7 tubes which may cause confusion as to the receiver's original designation. Additionally, the silk-screen was not changed for the chassis, so many CSR-5A receivers will have modified 6SK7 to 6SG7 tube identification.

The CSR-5 has eleven tubes in the receiver with two RF amplifiers, Mixer (also provides Xtal Osc function,) LO, two IF amplifiers, NL, Det/1AF, AF output and Voltage Regulator. The RF Gain control is a stepped attenuator type with about 10db of change for each step. AF output is 2 watts into a 10K Z load for loudspeaker, 500 ohms Z line audio and both Hi-Z and Lo-Z 'phones. A separate power supply is required and the VP-3 provided 12vac Filament (series/parallel connections for all 6.3vac tubes except the BFO and LO that use series resistive loads) and +250vdc B+ with an input requirement of either 12vdc (vibrator PS) or 115/230vac. An AC only power supply was also available and designated as the WE-11. Two 6X5 rectifiers are used in the VP-3 bringing the receiver's total tube count to 13 tubes. The later version CSR-5A was mostly built after the initial contract of CSR-5 receivers although it could be possible that the production overlapped. CSR-5A receivers were built up into 1945. The receivers were used actively through most of the 1950s.

The CSR-5 and 5A are found in a variety of different paint colors with the most common color found being a smooth finish, light cream color with a slight greenish tint. Smooth gray is also found when the receiver was part of a rack system. Gray wrinkle finish is common in the stand-alone receivers. Different shades of gray are often encountered along with black wrinkle finish. Many different shade and texture variations will be found along with both black or white nomenclature. Some paint combinations are original but most of the unusual variations are from military repaint jobs. The CSR-5 shown in the photo above has the name plate mounted on the front panel. This is not standard as most receivers have the name plate mounted on the top lid of the cabinet. Only the CSR-5A will have the "Marconi" script along with "CANADA  CSR-5A" silk-screened on the center area of the escutcheon. The CSR-5 is a good performer with all of the characteristics (both good and bad) found in mid-forties military receivers. Due to the VR tube and filament loads on the LO and BFO tubes, the CSR-5 exhibits very little drift after a short warm-up. Sensitivity is competitive with mid-1940s designs and although a crystal filter is included it doesn't have a front panel phasing control. 

Mackay Radio & Telegraph Company  -  Type  3001-A

The Mackay Radio & Telegraph Co. Type 3001-A is a Longwave regenerative receiver covering 15kc to 640kc in four bands and dates from as early as 1948 but with most manufacturing dating much later. The receiver shown was built in 1952. Mackay receiver serial numbers generally incorporate the last two digits of the year of manufacture as the first two digits of the serial number. The 3001-A was mainly for commercial shipboard (non-military) use where it could be set up as the main receiver or as the emergency receiver. The receivers were sometimes installed in the Mackay "Marine Radio Units," like the MRU-19/20, a shipboard radio console which contained two 3001-A receivers along with transmitters and other auxiliary equipment (the MRU receivers were panel mounted.) The 3001-A uses an AC-DC circuit and can operate on 115vac or on batteries. Various filament battery options were available with 6vdc, 12vdc and 24vdc being the most popular. B+ was supplied by standard dry cell B batteries when used. The receiver uses a four pin Amperite ballast tube along with six octal tubes. A small built-in speaker provides for radio room monitoring but earphones would normally have been used by the shipboard radio operator. The purple (when illuminated) dial provides a unique visual experience when tuning in the various signals. Selectivity is controlled by a combination of the RF Gain setting and the setting of the Regeneration. The 3001-A is very sensitive and capable of receiving any of the NDBs and other LW stations found in the spectrum below 500kc. These type of Mackay receivers were in use for several decades and were commonly found still operating on commercial ships as late the 1990s. These types of Mackay receivers date from the late forties and were manufactured through the fifties. (See our "Vintage Longwave Receivers" webpage for an in depth article about this receiver.)

1950 Collins 51J-2

Collins Radio Co. - 51J Series
(includes 51J-1, 51J-2, 51J-3, R-388/URR and 51J-4)

Introduced in 1949, the 51J series was developed as a general coverage receiver primarily for military, commercial or individual/enthusiast use providing accurate frequency readout and great stability. The receiver utilized a permeability tuned, double conversion circuit using the 70E-7 PTO in a dual, tuned-IF system and a multiple frequency crystal oscillator to cover .5mc to 30.5mc in thirty (1mc wide) bands. Dial accuracy is maintained at 1.0kc throughout the tuning ranges by limiting the coverage of each band to 1.0mc. Band 1 actually is triple conversion but only to allow coverage of the AM BC band. Bands 2 and 3 are single conversion while all of the remaining bands are double conversion. 16 tubes are used in the 51J-1 and J-2. The ham bands are high-lighted in green on the megacycle drum dial but, at nearly $900, not many hams could afford a 51J as their station receiver. Early versions have a metal dial bezel, the Collins' "winged emblem," no grab handles and an illuminated S-meter. Audio response is restricted at 200 to 2500Hz and is definitely not high fidelity, usually sounding somewhat "muffled" when receiving AM voice signals. The most apparent difference between the 51J-1 and 51J-2 is that the latter added an Audio Output function to the Carrier Level meter that was actuated by a toggle switch next to the meter. Some later production 51J-2 receivers may be found with the 70E-15 PTO installed but whether this was a post-sale retrofit or a Collins engineering-production upgrade is unknown at this time. In 1952, the 51J-3 was introduced, featuring an 18 tube circuit (adding a voltage regulator and vfo buffer,) a new version of the PTO (70E-15) and eliminating the fixed 300 ohm Z antenna input (by removing the primary winding on the antenna coils) and redesigning the antenna input to a more flexible design with an Antenna Trim control. This revision was at the request of the Signal Corps, who wanted to use the 51J receiver for their teletype installations but found the fixed 300 ohm Z antenna input requirements difficult to work with as most of their installations used either dipoles or vertical whip antennas. The military had their version of the 51J-3 designated as the R-388/URR and it was built from 1952 through about 1955. With the R-388 and 51J-3, grab handles were added to the front panel along with a high quality Burlington Co. sealed meter. In 1955, the 51J-4, with 19 tubes and three mechanical filters (.8, 3.1 and 6kc,) became available and was offered up to about 1964. The 51J-4 added a fourth stage of IF amplification to compensate for the insertion loss of the mechanical filters. The 51J-4 and R-388 are the ultimate evolution of the design but the earlier 51J-1 and J-2s have their own appeal and can provide top-notch reception. Though thousands of R-388 and 51J-4 receivers were produced, not very many 51J-1 or 51J-2 receivers ever turn up indicating that their production was at a fairly low level. Shown in the photo above is an early 51J-2 from 1950.

Reworking the 51J Receivers- If you are working on a 51J-2 receiver be aware that the 1950 version of the 51J-2 manual is fraught with errors in almost every section, but especially in the receiver alignment section, circuit description section, the component designations and component identification layouts. Another thought for consideration is that most of the earlier 51J-1 and 51J-2 receivers have had thousands of hours put on them by former commercial/military users. These receivers were sometimes roughly treated and are usually well-worn, needing much more than the usual re-cap and alignment to function at their design level of performance. The early 51J-1 & 2 gear boxes have brass drive gears where the later R-388/51J3,4 versions have steel drive gears. Sometimes the wear on early gearboxes is so severe that binding and jamming are experienced when changing the Megacycle position. The IF transformers often seem to sustain internal damage with rough handling of the receiver requiring disassembly and re-gluing of the coils and ferrite shields back into their proper position for correct operation. The R-388 and 51J-4 receivers seem to be in much better overall condition and usually don't require extensive rebuilding. However, there are some component quality issues (certain types of silver mica capacitors) that affect the AVC circuit performance. Also, the PTO end-points on nearly every R-388 PTO are excessive and beyond the range of the adjustment capacitor. The end-point issues are related to the quality of the ferrite slug material and require internal PTO compensation coil trimming to correct. You will also find that a separate voltage source must be provided to remotely switch the receiver to stand-by on all R-388, 51J-3 and 51J-4 versions. The earlier 51J-1 and 51J-2 receivers have a conventional remote stand-by circuit that parallels the front panel "STAND BY" and "ON" functions.

Performance - As to the 51J/R-388 performance overall, most of the 51J/R-388 receivers were used for data reception such as RTTY where the severe audio limitations made sense. For AM BC reception and SW BC reception the receivers might be disappointing to some ears because of their limited audio reproduction of 200 to 2500Hz. Stock 51J receivers do sound a bit "muffled" in AM reception but changing the value of the capacitor that is across the audio output transformer primary from .01uf to .001uf will increase the audio highs somewhat. There are also issues with the AVC circuit which never seems to function very well however the components used the AVC circuit are chronic suspects that always need to be replaced for proper operation. Product Detector mods are most common and involve changing the BFO from a 6BA6 to a 6BE6 mixer tube to accomplish the circuit modification. There are mods galore to the 51J/R-388 AVC and BFO circuits however the usual modification caveats that should be carefully considered before hacking up the receiver.

Dial accuracy and stability - both necessary for RTTY work - were the 51J selling points to the Signal Corps and still are the 51J's primary attributes today. Although the stock audio is somewhat restricted, the receivers are great performers providing they have been thoroughly rebuilt and fully aligned. Additionally, the 51J/R-388 receivers are the best looking of the Collins receivers with a beautiful layout of the two dial system that allows separate megacycle and kilocycle readouts direct along with the added benefit of general coverage reception from .5mc to 30.5mc.

1953 Hammarlund SP-600-25C

Hammarlund Manufacturing Co., Inc.  -  SP-600 Series

Introduced in 1950 and selling for nearly $1000 at that time, the SP-600 was intended for the military and commercial user market. It was a very popular receiver and many thousands were built, especially for military applications. Though most versions were built throughout the 1950s, the SP-600 continued to be produced in smaller numbers up into the early 1970s. The standard SP-600 tunes from .54 to 54MC in six bands. A "J" suffix indicates JAN parts were used in the construction and an "X" suffix indicates a switchable crystal LO. Hammarlund also offered a "JL" version with 100-400KC substituted for the .54-1.35MC band and a "VLF" version that covered 10-540KC. Hammarlund made over 40 variations that were assigned a numerical suffix which identified the particular circuit, mechanical changes or sometimes the end-user. The last in the "time-line" was the model variation SP-600 JX-21A from 1969-1972 which utilized a product detector circuit, two additional tubes and some other changes to make it "compatible" with SSB operations.

Most versions use a 20 tube double conversion superheterodyne circuit with a rotating turret bandswitch. The receivers also feature enormous proportions, robust construction and oversize controls - along with a super-smooth tuning system that only adds to the enjoyment of operating these fine receivers. Double conversion is switched in above 7.4MC and uses a crystal controlled conversion oscillator. Though the SP-600 has two dials, it has no bandspread - the right side dial is a logging scale allowing precise retuning of desired stations. On the left is the main tuning dial and the mechanically articulated dial pointer that indicates which tuning scale is in use (along with the small window between the dials that shows which tuning range is selected.) The tuning arrangement was an up-dated version of the "Continuous Bandspread" system introduced in RCA's AR-88 series receivers in the 1940s. The frequency readout accuracy is vague which is why a precise logging scale system is incorporated into the SP-600 design. The meter is not illuminated and a switch is provided to indicate either carrier level or audio output. Most (but not all) SP-600 model numbers usually will have a suffix with "J" or "JX" followed by a numeral. As mentioned above, suffix "J" indicated that, as much as possible, military level components and construction were used. Suffix "X" indicated that a switchable six-position, fixed-frequency crystal-controlled oscillator was installed that allowed the user to install HC-6/U type crystals for specific desired LO frequencies. The user could switch to any of the crystal LO frequencies for increased stability for that particular frequency - however, the receiver still has to be "tuned" to the desired frequency for the RF and Mixer stages to be in tune. Many SP-600 receivers were set-up for diversity operation and the standard diversity model was the JX-17 version. This version was produced in large numbers and can be easily spotted by observing that it has two extra controls and uses three red colored knobs. The SP-600 Audio output is about 2 watts from a single 6V6 using a balanced split-winding audio output transformer for 600 ohms Z. The audio quality from a rebuilt SP-600 is impressive communications-grade audio with the lower end rolled off at 125Hz 3db down. This audio shaping, while noticeably lacking bass response, was designed into the SP-600 to allow excellent copy in all modes whether it be CW, RTTY (or other data modes) along with great intelligibility of weak signals in voice modes (either AM or SSB.)

The number following the letter suffix generally indicates specific features for that version, e.g., contract or end user, circuit upgrades, etc., with the number ranges being more or less chronological until the last of production. Though the number suffixes were more or less chronologically assigned, many of the versions were built over a fairly long time period. This meant that engineering and component changes were being added as receiver production continued. The end result today is that there are early and later versions of many of the numbered suffix models and documentation is not always specifically accurate based just on the number suffix. It is more accurate to use the build date of the receiver and use documentation that is dated close to the receiver manufacture date.

It is interesting to note that Hammarlund did not refer to the SP-600 as a "Super-Pro" receiver in their manuals and only occasionally is its "Super-Pro" lineage mentioned in Hammarlund advertising. The inset photo shows the SP-600 JX-21 version from 1953. The JX-21 was generally used by the USAF. This is the early version of the JX-21 - so it does not have the product detector SSB changes. The header photo shows the SP-600-25C built for the US Army Signal Corps and it is housed in an original SP-600 cabinet. The SP-600-25C version has the large square 25-60 cycle power transformer and does not have the switchable crystal oscillator ("X" option.) SP-600 cabinet colors vary from dark charcoal to light gray depending on when they were manufactured. A rebuilt SP-600 is a pleasure to operate with incredibly smooth tuning, competitive sensitivity, a great selectivity set-up featuring six positions that include three crystal filter positions and, of course, its massive controls and domination of the ham station landscape.

 the Hallicrafters, Inc.  -  R-274D/FRR (aka: SX-73)

Shortly after Hammarlund began building the SP-600 for various military contracts, the military began accepting alternative designs for high-performance receivers that could replace the SP-600, if necessary. Hallicrafters is the only company that was successful in submitting an alternative design that was accepted by the military. The Hallicrafters receiver was produced as the R-274D/FRR designation. Interestingly, Hammarlund also built SP-600 receivers with designations of R-274 with A, B and C suffixes. Apparently, only one contract of Hallicrafters R-274D/FRR receivers was produced for the military. The typical military contract production quantity was for around 5000 receivers and it doesn't seem likely that Hallicrafters would have gone through the effort for a smaller contract. It's also possible that Hallicrafters thought there would be more contracts in the future but that doesn't seem to be the case. Since Hallicrafters had invested in some production line tooling and had obviously set up component suppliers for production, they decided there might also be a commercial or even a ham market for their receiver. The civilian designation assigned was SX-73 and these receivers are virtually identical to the R-274D except for the ID tag, which shows "SX-73" as the receiver type. Some advertising mentions that a cabinet was supplied with the SX-73 though advertising artwork generally shows the receiver in the rack mount configuration. Selling price was quite high at $975 which certainly limited purchases of the SX-73 by the civilian market. The SX-73 version is seldom seen and production must have be very limited. The R-274D and SX-73 were available from late-1951 up to around early-1954.

The R-274/SX73 is generally referred to as "Hallicrafters' version of the SP-600" or the "Hallicrafters' Super-Pro" since there are so many similarities between the two receivers. The similarities are to be expected since Hallicrafter's design had to meet Signal Corps specifications that essentially described the "basic" SP-600. The most obvious similarity is the turret band switch which, while functionally the same at the SP-600's, is not nearly so robust in construction using fiber board modules while the SP-600's are made of ceramic. The tuning dial provides a main dial and a logging dial as the SP-600 does but behind a single escutcheon rather than separate dials behind two escutcheons. There is a selectable six channel Crystal Oscillator that functions like the SP-600 "X" option and provides improved stability for RTTY and other data modes. Like the SP-600, the bandwidth is selectable in six selectivity steps with three of those steps using a Crystal Filter for narrow bandwidth (a front panel Phasing control is also provided.) A 600 ohm balanced audio output is also similar to the SP-600 audio output.

One major difference between the R-274/SX73 and the SP-600 circuit is the conversion frequency of the SP-600 is 3.955mc while the R-274/SX73 uses 6.000mc. Also, the placement of the conversion frequency with reference to tuning range four has the double conversion starting at 7.0mc on the R-274/SX73 while it is 7.4mc on the SP-600. This results in double conversion being used for the 40 meter ham band on the R-274/SX73 but not on the SP-600. The R-274/SX73 frequency coverage of each tuning range is beneficial to the ham user in that 160, 80, 40 and 20 meters are on separate tuning ranges while the SP-600 combines 80 meters at the low end and 40 meters at the high end on tuning range three. In the audio section of the R-274/SX73, the coupling capacitors are .01uf in the R-274/SX73 while the SP-600 uses .0015uf capacitors. This results in the "communications-grade audio" found in the SP-600 while the R-274/SX73 has a more conventional audio response. Additionally, the R-274/SX73 provides an Antenna Trim control while the SP-600 does not. Possibly the most important difference between the R-274/SX73 and the SP-600 is that the former receiver utilizes almost entirely ceramic disk capacitors in the circuit rather than the "leakage-prone" molded capacitors that have negatively influenced the reliability and reputation of the early SP-600 receivers. In considering the restoration of the R-274/SX73, the ceramic capacitors will certainly and positively reduce the amount of rework that is going to be necessary.

Some of the components used in the R-274/SX73 are of a better quality than those found in the SP-600 - IF transformers and the bulk of the capacitors used, for example. But some other parts and components are not as high of quality as those found in the Hammarlund - band switch turret, the dial gear train and the dial lock, for instance. The R-274/SX73 tuning dial itself along with the logging dial are difficult to read (some users find the same fault with the SP-600) and the R-274/SX73 dial illumination is feeble. The Carrier Level meter has only a Decibel scale that references 0db as mid-scale on the meter which is equal to 50uv input signal level. Performance is the final judgment though and the R-274/SX73 will easily provide the user the same high sensitivity and quality reception as the SP-600 along with much better audio reproduction.

1951 Collins R-390/URR in a CY-979/URR cabinet

Collins Radio Co.  -  R-390/URR & R-390A/URR

Arguably, the R-390/URR and its later kin, the R-390A/URR, are the ultimate tube-type receivers. The first version of this incredible receiver was the R-390 featuring 33 tubes (includes the 3TF7 ballast tube,) double or triple conversion, two RF stages, six IF stages, modular construction, three audio filter settings, six selectivity bandwidths and frequency coverage from 500 kc. to 32.0 mc. in 32 - one megacycle wide - bands. It is a high performance receiver that really "shows its stuff" when conditions are poor but will also provide fairly nice audio quality when receiving conditions allow for it. The most common complaint is the cumbersome tuning that, while "parked" on one frequency is not apparent, shows up when spanning an entire band or changing ranges. Most of the "stiff tuning" complaints can be traced to an over accumulation of grease and dirt in the gear train. When clean and properly (lightly oiled) lubed, the tuning is very light and easy to manipulate. Only Collins or Motorola built the R-390 contracts which ran from 1951 through 1953. The military complained that the R-390 was very difficult to maintain and too expensive. Some of the maintenance issues involve the R-390's elaborate electronically regulated B+ circuit that uses two 6082 tubes along with two 5651 voltage reference tubes and a 6BH6 DC Voltage Amplifier tube. This circuit runs quite hot and accounts for many of the problems that develop in the audio module (where the regulator circuit is located.) Additionally, the R-390's gear train has a moveable "locking gear" that must be installed prior to removing the RF module (if you want to keep everything synchronized.) This gear was painted green and usually mounted with a screw on the front of the gear box. Each time the RF Module is removed and then replaced on an R-390, the KC and MC drive shaft split gears have to be reset for backlash, the Crystal Oscillator module's bandswitch has to be synchronized and the oldham coupler installed. Removal of any of the crystals in the Crystal Oscillator module requires removal of the hard-wired crystal oven. When the military complained about complex maintenance issues, they weren't exaggerating.

The R-390 and R-390A receivers have provided reliable communications under adverse conditions for years and even though the designs are over 50 years old, they are still one of the best tube-type receivers around. Many R-390 and R-390A receivers are still being used today, some in professional applications, but also for serious SWLing and, of course, in vintage ham stations around the world. Many AM operators prefer the R-390 version for its better over-all sound quality when listening to SWBC or AM stations in general, however one must consider the maintenance challenges when selecting the R-390 for a station receiver. Nowadays, many R-390 and R-390A receivers are being used in "as purchased" condition - that is, the receiver has not been rebuilt, restored or even thoroughly serviced and properly aligned (or is it "alined?") The performance of a fully functional, rebuilt (restored) and recently aligned R-390/390A is incredible.  Below is a short description of what happen to thousands of R-390A receivers when they were decommissioned by the military. St. Julian's Creek Annex has become famous for their outdoor storage of thousands of R-390A receivers.   photo right: Motorola 1956 contract R-390A. The early  Collins and Motorola panels had silk-screened nomenclature rather than engraved nomenclature. By 1957, all front panels were engraved.

1961 contract manufactured by Capehart with OD front panel

R-390A  - End-User Front Panel Repaints

From time to time, R-390A receivers will show up with the front panel sporting a non-standard paint color. The original specification only calls for the panel to be painted gray. Consequently, many shades of gray are found from the many different contractors that built R-390As over the years. Sometimes though, completely non-standard colors will found and these are always "end-user" applied paint jobs. The most commonly known "end-user" paint job is the USAF's flat-black panels. There is a well-known B&W photograph of the installation showing several R-390A receivers with black panels and what looks like non-painted knobs. Several years ago, a 1961 Capehart contract R-390A with an olive drab painted front was found in the Northern Nevada area. It had been supposedly repainted by the USMC. Here is another 1961 Capehart with the OD painted front panel, also found here in Northern Nevada, in 2009. All R-390A receivers left the contractor's facility with gray panels - it was the specification - but the "end-users" were liable to repaint during a rebuild so anything might be possible - just not original.

Nems-Clarke, Inc.  -  1302 Special Purpose Receiver

Allen Clarke started in the electronics design business in the 1940s and by 1951 had a small electronics design business. NEMS was an acronym for National Electric Machine Shops, a name chosen by NESCO, National Electric Supply Company, when they incorporated in 1937. NESCO goes back to 1899 and the company was involved in radio manufacturing very early with many contracts assigned to them in WWI and after. NEMS and Clarke merged in 1955 as Nems-Clarke - specializing in high-end commercial-military radio equipment. All (?) Nems-Clarke receivers operate in the VHF and UHF part of the spectrum that was then being used in part for telemetry from some kinds of missiles and for other military and quasi-military purposes. Later Nems-Clarke receivers monitored Russian missile launch telemetry. The 1302 Special Purpose Receiver is a VHF AM/CW/FM receiver that utilizes a Western Electric 416A Planar Triode tube in the front end. The 416A operates at a very high temperature and is cooled by a small forced-air blower. The receiver tunes from 53mc up to 262mc in one continuous coverage tuning range with a 0 to 35 scale for logging. The tuning dial is not illuminated. Behind the grille on the left side of the panel is the built-in four inch speaker. The 1302 was designed to operate with a matching Spectrum Display Unit, (SDU) or Panadaptor.  The upper zero-center meter is for tuning FM and the lower meter shows relative signal strength and can be used for tuning AM signals or measuring relative FM signal strength. The 1302 was primarily used for surveillance by several different government users. Later versions of the 1302 use a different front-end tube (7007) and are styled more like the Nems-Clarke receiver shown below.

Nems-Clarke (Vitro Electronics) - 1306-B Special Purpose Receiver

Nems-Clarke was purchased by Vitro Electronics in 1957. Nems-Clarke/Vitro continued to produce Special Purpose Receivers for surveillance and telemetry that were used throughout the late fifties and sixties. The 1306-B Special Purpose Receiver is a 29 tube AM-FM-CW receiver that was usually operated with a SDU-200-6 Spectrum Display Unit (panadaptor.) The receiver tunes 30mc to 60mc and 55mc to 260mc with separate dials for each band that are only illuminated when in use. Selectable IF bandwidths, selectable IF AGC/Manual Gain controls, Squelch and a BFO with variable Pitch Control are provided. The zero-center meter provides accurate tuning for FM signals while the right hand meter measures signal strength. The built-in speaker is a very small "communications quality" unit that is located behind the screened cover. A 600 ohm audio line is provided on the rear panel can provide excellent audio quality to a matched loud speaker. The "SPEAKER" switch is a factory modification that replaced a PHONE jack with a switch to silence the panel speaker. Many of the Nems-Clarke surveillance receivers were used to monitor Russian missile launches and analyze data transmissions along with any voice traffic. The 1306-B is a great performer with an impressive appearance.

National Company Inc.  -  HRO-5TA1 

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 HRO-5TA in 1946 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 switch to metal octal tubes and the use of mostly JAN parts. The 1946 coil sets now used a single aluminum plate with silk-screened graphs and the toggle switch functions were now identified (these toggle switch IDs were actually on the late WWII models also.) The first HRO-5TAs were nearly the same as the late WWII receivers except for the return of the amateur bandspread function to coil sets A,B,C and D. In a short time, the HRO-5TA1 replaced the TA and added a noise limiter to the circuit. The TA1 used 12 tubes - two additional tubes were necessary for the noise limiter circuit. Early versions of the TA1 will have the round S-meter but a square S-meter was used on most of the production. Unbelievably low noise in combination with high sensitivity and incredible bandspread make the HRO-5TA1 one of the best receivers for a vintage ham station. Of course, the micrometer dial (while super-smooth for tuning) does not allow for accurate frequency read-out, but in 1946, most hams had a Frequency Standard (a 1.0mc./100kc. xtal. oscillator) in the shack and many were still using crystal controlled transmitters. As always, the accurate resetting ability of the micrometer dial was unbeatable. When set up for bandspreading, the micrometer dial tunes each ham band in 400 divisions, or the equivalent of a linear dial nine and a half feet long. Though the HRO-5TA1 is an excellent ham band receiver, it isn't found in too many vintage ham stations these days, probably because it requires several accessories and the dial readout must be correlated with graphs to determine tuned frequency. Additionally, it uses a single-ended audio output, the dial is not illuminated and the receiver has a rather basic appearance.

In mid-1946, an HRO-6 was produced in a very small production run that used the same numerical designation as the HRO-5TA1 production run, 184. It appears identical to the HRO-5TA1 externally and the only difference between the two receivers is a slight change to the Noise Limiter circuit. 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. Internally, a voltage regulator was added and the LO changed to a miniature tube. Basically, the HRO-7 was pretty much the same as its predecessor but with a modern cabinet.

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 actually set-up a regenerative oscillation in the IF. 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 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 in 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. 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 and weighs in at over 100 lbs. The PA tube is a Raytheon 4D32 with selectable plate voltage - either 600 or 700vdc -  the lower voltage allowing the 4D32 to run at the manufacturer's specifications for continuous duty. The modulator tubes are 807s. The power output is generally around 100 watts. If the 32V-2 is conservatively operated, 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.

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 pairs of 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. Low-end tracking suffers on coils sets A and B when the incorrect conversion frequency is used. When properly aligned, 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 about a couple of years, I traded the HRO-60R to NU6AM for a really nice National FBX receiver with the band spread coil sets. A while later, NU6AM traded it to K6DGH who in turn sold it to KG6YV. All of the trading and selling took place over several years. Around 2003, I asked NU6AM if he knew the whereabouts of the HRO-60R and he 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 about 12 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

Hammarlund Manufacturing Co., Inc. - HQ-140X

The HQ-140X was the next evolution of the famous and popular HQ-129X. It essentially revamped the circuit to use more modern miniature tubes and to provide a separate LO tube and separate mixer tube rather than the single converter tube used by its two predecessors - the pre-war HQ-120X and the post-war HQ-129X. Eleven tubes are used in the circuit including one RF amplifier, three IF amplifiers and a voltage regulator tube. The high quality audio is from a single stage 6V6 providing just a few watts of power. It was around this time that Hammarlund switched from using tubular capacitors in their circuitry to ceramic disk capacitors and the HQ-140X is one of the first receivers to use almost all ceramic disks making major cap replacement unnecessary today. Of course, there are still the electrolytic capacitors and three paper tubular caps to deal with. The brown knobs of the earlier HQ-140X gave the receiver a unique look that must not have been very popular as later models sported dark gray-black versions of the knobs. The HQ-140X sold for around $250 and was offered from 1953 up to 1955 when its successor, the HQ-140XA, came on the scene for another few years. 

Hammarlund Manufacturing Company, Inc. - HQ-110

Hammarlund introduced the "ham bands only" HQ-110 in 1957 as an entry level version of the HQ-170. The HQ-110 covered 160 meters up to 6 meters and was double conversion on 40 meters and above. The circuit used 12 tubes and included a Q-multiplier, S-meter and Noise Limiter. Many of the tubes used are multi-section tubes providing dual and triple functions in the circuit. The "C" suffix included a clock on the left side of the panel. The HQ-110A came out in 1962 and added a few extra features. An HQ-110 VHF was also produced that added 2 meters. The selling price of the HQ-110 was fairly high at around $230.

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 "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 wired and $149.50 as a kit. Only 840 Navigator transmitters were produced. The Navigator shown was donated to the museum by K6QY.

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. 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.

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.

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, 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."

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 little better than communications grade. 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 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. 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. For the past 40 years, they have been my regular SSB/CW station.

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.

The KWS-1 is capable of 1KW 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 coverts 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 650W DC. In the AM mode, the carrier is re-inserted 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 "strict DSB AMers" but, unless mentioned, many 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 400W input. In the CW mode a full 1KW 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 the 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 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 K6RIM, Al, in December, 1970. Al had purchased the KWS-1 used in 1960 from Amrad Electronics in Burlingame, California (later 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. Lately, I've been using the KWS-1/75A-4 on AM on the West Coast Military Radio Collector's Net where it provides a unique type of AM for enthusiasts to hear - one sideband with carrier. The KWS-1/75A-4 have a long association with military MARS stations and, of course, the SSB promotion that involved the Air Force in the mid-fifties. The KWS-1 is certainly one of the best from the "Golden Age of Ham Radio."