Western Historic Radio Museum

THE COLIN B. KENNEDY COMPANY

"RADIO APPARATUS OF QUALITY"

                    Receivers -  Universal  Type 110
                                          Intermediate Wave Type 220
                                          Short Wave Type 281
         Audio Amplifiers -  Type 525 & Type 521

History, Circuits, Performance
Using Kennedy Equipment Today

by: Henry Rogers WA7YBS/WHRM

 

Kennedy Universal used "portable" circa 1923. Also note the Magnavox amplifier on the running board and Magnavox R-3 horn speaker on the Kennedy along with the earphone sets hanging from the car's top and the loop antenna on the hood. A real first-class portable receiving station.  Photo from the Henry Ford Museum and Science&Invention Magazine

Differences in San Francisco and St. Louis Manufacture - After the move, in June,1922, Kennedy receivers made in St. Louis changed rather quickly in subtle details. This was probably due to different tools for manufacture, possibly different personnel, different suppliers of materials and the expected evolution of radio design. In San Francisco, the receivers used all metal binding posts which was due to the handmade nature of all of the parts. In St. Louis, bakelite capped binding post were used, probably supplied by an outside source. Tube sockets used in early receivers were supplied by General Radio or Paragon but later receivers made in St. Louis will have Kennedy marked sockets. The knobs become molded pieces in St. Louis. In San Francisco, the  receivers had early circuitry, e.g. a plate potentiometer adjustment control on the large sets and extra Antenna Tuning range on the shortwave receiver. These controls were simplified or eliminated in the St. Louis manufacturing. As receiver technology evolved, so did the Kennedy receivers. It is common to see many differences when comparing earlier San Francisco receivers with later St. Louis versions.  

The Universal Receiver - Type 110

The Kennedy Universal Receiver Type 110 was introduced in July, 1921. Its heritage comes from Kennedy's early receivers, the Type 100 and the even earlier LWR-20. Its incredible tuning range starts at 150 meters and ran all the way to 25,000 meters - that's from 2.0mc down to 12 kc. "Universal" meant that it would tune in anybody that was on the air in 1921. Though the advertised shortest wavelength was 175 meters, or about 1.7mc, I have found that most Universals will tune up to 2.0mc, or 150 meters (in fact, this applies to the Type 220 and Type 281 as well.) The Type 110 is a three-circuit tuner utilizing a regenerative detector designed originally for the detector tubes available in 1921. Later manuals and advertising specify the UV-200 "soft detector" tube. The UV-200 was also known as a "gas" detector tube since it had some argon inside the envelope. These detector tubes require a little time to come up to full sensitivity, usually about 5 minutes warm-up is sufficient.

 The Primary circuit uses a tapped inductance that can be set to nine different positions each of which can be tuned by the Primary condenser, either connected in series or parallel. The Primary circuit is essentially an Antenna Tuner and, with proper adjustment, maximum signal levels are inductively coupled to the Secondary circuit using a variable Coupling coil. The Secondary circuit uses a tapped inductance that can be set to seven different positions and tuned with the Secondary condenser. The Secondary circuit tunes the detector input to the incoming signal from the Coupling coil which is located inside the Primary Inductance. The Coupling coil rotates 180º which varies its position relative to the Primary Inductance's axis and therefore couples more or less signal energy to the Secondary circuit. The Regeneration is tuned with a variometer in the detector plate circuit. With variometer controlled regeneration the plate circuit is tuned to the grid input frequency and the feedback path is via the interelectrode capacitance of the detector tube. Since the Primary circuit maintains a fairly constant load on the detector grid circuit (Secondary circuit,) the Regeneration control settings are always within the range of the variometer to tune and thus control the amount of feedback and the detector sensitivity. The variometer also has a set of Secondary-Regeneration loading coils mounted below the variometer to assure enough feedback is available at the longer wavelengths. A variable condenser is used as the grid-leak condenser so that optimum performance can be achieved on all wavelengths.

photo above: The Kennedy Universal Receiver Type 110, St. Louis version, SN: 5403  ca: 1922-23. This example is a beautiful condition, all original, functional receiver.

This Universal was almost destroyed in a 1984 house fire. Fred Winkler, who was an old collector friend of mine, had only seconds to make a decision before escaping his burning house - which radio to save. He grabbed this Kennedy under his arm and rushed out of the burning house. Unfortunately, the rest of Fred's radio collection was destroyed along with most of the house. I purchased this Universal from him in 1994.

photo above: The impressive interior of the Kennedy Universal Receiver Type 110, St. Louis version. Note that the bank wound inductances are yellow-orange color from the amber shellac used to seal the coils. In front of the detector tube is the variable grid-leak condenser. To the left of the detector tube is the variometer and regeneration loading coils.

The quality of construction and components used on the 110 is impressive. The bank-wound inductances are necessary for wavelengths longer than 1000 meters and this method of coil winding reduces distributed capacitance and prevents oscillation at unwanted frequencies. Cotton covered Litzendraht wire is used for the coils which were given a coat of amber shellac to protect and secure the windings. Kennedy advertising implied that the coils were "moisture-proof" because of this coating. The variometer uses a molded bakelite housing and rotor which results in a precision instrument for controlling regeneration. Due to the very long wavelengths that the 110 can tune to, a dual secondary condenser is used. On band 7, the additional variable condenser is switched into the circuit to allow the 110 the ability to tune down to 12kc, or 25,000 meters. Additionally, the two largest bank-wound inductances are connected in series on band 7 to further allow tuning to this very low frequency. The Inductance switches are point contact types that are mounted behind the panel with pointer knobs and numerals engraved on the front panel to indicate which inductance tap was switched in.

Early 110 receivers will have a Plate Potentiometer adjustment which is a fairly high value variable resistor connected across the A battery terminals with the receiver B- connected to the arm of the variable resistor. This allowed electrically adding the A battery voltage to the detector plate battery voltage. With an 18vdc detector plate battery, the operator could adjust the Plate Potentiometer to any detector plate voltage from 18 to 24vdc. This control was eliminated from the later 110 production for several reasons. First, if left connected up it was a drain on the A battery. Second, the UV-200 production was more predictable in its filament to plate voltage ratio and the operator could accomplish more or less the same effect by raising or lowering the filament voltage.

I've owned this Universal for over 25 years. I purchased it from Paul Giganti. It was the victim of several modifications, as many Type 110s were, so I performed a complete, authentic restoration on the receiver to return it to original condition and to be fully functional . I won first place in  Radio Age's Radio Reception Contest in the late eighties using this SF Type 110 with its matching SF Type 525 Audio Amp. I entered in the category "Regenerative Receivers."  I only tuned in 26 AM BC stations because I had to wait for each BC station to ID themselves which used up most of the time allotted for the contest. I don't know how I won with only 26 stations logged - no competition, I guess.

The Universal required a six volt storage battery for the A supply. Today, any well filtered 6vdc power supply that is capable of a few amps is sufficient. The Detector B+ is usually around +22.5vdc. The pure tungsten filament UV-200 tube requires 5vdc at 1A, although most good emission tubes will run with fine sensitivity at about 4.5vdc.Unfortunately, pure tungsten has a finite life and when tungsten filament tubes have weak emission there is nothing that will bring the filament emission back and the tube must be replaced. 

When using just the 110 receiver with no audio amplifier, a good set of earphones is necessary. Baldwin 'phones with their direct-driven mica diaphragms have the best sensitivity, sometimes equivalent to a single stage of audio amplification, when compared to standard ferrous-diaphragm 'phones. If the Type 525 Two-Stage Audio Amplifier is going to be used, the A supply will have to be capable of supplying at least four amps (one amp "headroom.") The Universal's Telephones output is strapped to the Type 525 Input and the 'phones connected to the Type 525 Output. Detector, 1 Audio Amplifier or 2 Audio Amplifiers can be selected by inserting the corded telephone plug into the appropriate phone jack. The Type 525 filament controls will determine the amplifier gain. Horn Speakers can be driven by the Type 525 but only for Broadcast reception, the other signals generally being too weak to be heard in the loud speaker.

The last of the 110s were offered for sale in April, 1925. That the advertisement was in QST seems to imply that the general radio buying public probably wouldn't have been interested in a large, difficult to use, regenerative receiver in 1925 but, maybe the hams might be interested. For the QST sale price of $95, the 110 was a bargain for anyone who wanted to own one of the best built radio receivers of the time. The original selling price in 1922 was a staggering $250.

The Intermediate Wave Receiver - Type 220

The Kennedy Intermediate Wave Receiver was introduced in 1921. Its appearance is similar to the earlier SWR-6 but that receiver tuned in the Short Waves. It is also similar its immediate predecessor, the Type 200 (though the Type 200s tuning range is also usually specified as Short Wave.) The Type 220 was built to the same high quality that the Universal Receiver was but the tuning range was from 150 meters up to 3000 meters, or about 2.0mc down to 100kc. This is a good portion of the Medium Wave part of the spectrum, so the Type 220 was designated as an Intermediate Wave Receiver. The Type 220 circuitry is essentially the same as the Universal with adjustments made to the coil and condenser size due to the receiver's reduced tuning range. One readily apparent difference is the mounting of the inductance switches which are fully visible with front panel mounting. Other differences, besides the smaller physical size of the receiver, are the Coupling and Regeneration controls sport matte silver-plated dials and the Filament control is a knob with no scale. There is normally no fine tuning adjustment knob on the Secondary condenser, however, sometimes the Type 220 will be seen with the fine adjustment feature. Whether these were upgrades done by dealers or from the factory is not known. The filament voltmeter was not used in the Type 220.

The Type 220 went through the same evolution as the Universal so early versions, made in San Francisco, will have nickel-plated binding posts and a Plate Potentiometer control while the later St. Louis versions have bakelite capped binding posts and no Plate adjustment. It is normal to find the Type 220 coils coated in clear shellac (while most Type 110 receiver coils are coated with amber shellac.) While most components aren't interchangeable, the same quality and style of manufacture is used in the Type 220 as with the other Kennedy equipment.

It is interesting to note that the Type 220 shown in the photos (sn 5118) was 10 seconds from being thrown into the Carson City, Nevada dump back in 1986. It had been in a chicken coop that was being "cleaned out" and was considered merely more junk to be discarded. My old radio collector friend, Fred Winkler, happened to be at the dump at the same time and saw the Type 220 about to be hurled onto the heap.

photo above: The Kennedy Intermediate Wave Receiver Type 220, early St. Louis version, SN:5118.

 A dump rescue, this receiver in now fully restored.

photo above: The component side of the Intermediate Wave Receiver

Fred's phone call to me started out, "You know anybody that has a Kennedy variometer?"

"Yeah, me," was my reply.

"Well, come over. I have a Kennedy 220 for you that's missing the variometer."

I traded Fred a National RBL Longwave receiver for the Kennedy. The Type 220 needed a bit more than the variometer though. The cabinet was in pieces and needed to be reassembled and glued. The Regeneration loading coil assembly that mounts under the variometer had to be replicated. The filament pot needed to be rewound with Ni-Chrome wire. I had the correct dial for the variometer (Regeneration) but I didn't have the filament control knob. Luckily, I found one at a swap meet a week or two later. I had to make several of the bakelite caps for the binding posts. Also, I fabricated the thumb screws that hold the lid down. All of the hardware was re-nickel plated so that all of the pieces matched when reassembled. It was lucky that I already had the correct Kennedy variometer in one of my parts boxes. That piece would have been impossible to replicate.

The Type 220 works fine after its resurrection. Performance is similar to the Kennedy Universal in most ways. Tuning is limited to four bands. With its smaller dimensions, it would have seemed that the 220 would have been a popular receiver but it is not seen as often as the Universal Receiver. Selling price was $125, half the cost of a Universal, but it didn't seem to make a difference. In the 1921-1923 time period, most radio purchases were made by radio enthusiasts and they wanted the biggest and the best, which accounts for the somewhat limited popularity of the Type 220. 

Be sure to keep an eye out for the 1930 movie, "The Green Goddess," which features several good shots of a Kennedy 220/525 combo in the wireless station that figures in the movie's plot.

The Short Wave Receiver - Type 281

The Type 281 Short Wave Receiver was intended for the experimenter, radio fan or ham operator. It tunes from 150 meters to about 650 meters, so it would receive most of the popular transmissions in the early twenties. The Type 281 wasn't popular as a ham receiver, probably due to its somewhat high selling price of $90 when compared to similar Grebes or Paragons. The same Kennedy level of construction quality is used in the Short Wave Receiver but since it only tunes in the higher frequencies, the components are small and the receiver interior appears rather sparsely populated since there is an absence of large inductors or huge condensers. In keeping with the style of receiver that the hams would appreciate, black dials with silver nomenclature were used on the majority of  Type 281 receivers. There are some indications that some of the early San Francisco versions used matte silver plated dials but these are rare sets that are seldom seen. The earlier San Francisco version Type 281 also included a more elaborate Antenna Tuner with two sets of point contacts and only a single antenna binding post. The St. Louis version replaced the double tuned antenna tuner with a single set of switch contacts and added two antenna binding posts, "L" and "S", to increase the antenna tuning range depending on the type of antenna used. The "L-S" switch is for changing the tuning range from longer waves to shorter waves. A vernier tuner was added to the Short Wave Receiver that is actually a real vernier condenser rather than a mechanical "slow motion" control, as in the Universal Receiver.

photo above: The Short Wave Receiver Type 281, St. Louis version

I traded some Moorhead ER tubes and other early hand-made tubes to Will Jensby for this Kennedy Shortwave and the matching Type 521 amplifier. I've had this set for about 20 years.

photo above: The sparse interior of the Short Wave Receiver, St. Louis version

The Type 281 may not have been too popular with the hams but it is a great little receiver and performs quite well. Since it doesn't have to tune the long wavelengths, it is a very simple receiver with very few components. Also, since it tunes the shorter wavelengths, it seems to perform better because the majority of signals in that part of the spectrum are much stronger than the longwave signals. The Type 281 will receive ham signals on 160 meters and the hams running AM stations sound very good. When listening for CW signals, the detector must be oscillating and that ends up with a lot of hand-capacity problems making tuning difficult. SSB signals encounter the same difficulty. At the time the Type 281 was new, most hams were on damped-wave spark using rotary gaps which would have been received somewhat like a modulated-CW (MCW) signal, that is not requiring the detector to be oscillating.

Two-Stage Audio Amplifiers - Type 525 & Type 521

Kennedy offered two popular Two-Stage Audio Amplifiers that were intended for use with their regenerative receivers. The larger Type 525 was intended for use with either the Universal or the Intermediate receivers sold for $85. The smaller Type 521 was intended for use with the Short Wave Receiver sold for $55. Both amplifiers were two-stage, transformer coupled audio amplifiers that use "hard amplifier" tubes with pure tungsten filaments, the UV-201. These tubes require 5vdc at 1A to light the filament. When operating with a receiver, the total current requirement for this setup is 3A (or 15 watts.) These amplifiers can be operated with 201A tubes as long as the A supply has some adjustability to compensate for the limited resistance of the amplifier's filament controls. The amplification selection is accomplished by inserting the corded telephone plug into the appropriate phone jack for "D" (detector only,) "1" (det+1AF) or "2" (det+1AF+2AF.) The Telephone output on the receiver is "strapped" to the amplifier "INPUT" and the amplifier "OUTPUT" is used for either earphones or a horn speaker. Plate voltage on the tubes is normally around +60 to +90vdc. Although the manuals show +60vdc for the Plate voltage, I have found that these amplifiers work much better with +90vdc on the Plates.

The amplifiers follow the same basic evolution as the receivers. Note that the San Francisco version Type 525 has the phone jacks located at the bottom of the panel while the later St. Louis version has the phone jacks in the center of the panel. 

Operating any of the Kennedy receivers without an audio amplifier is a challenge when searching for DX signals. You need to use really good 'phones, like Baldwin Type C, to have enough audio on the really weak signals. A Two-Stage Audio Amplifier is a tremendous help in hearing the really weak ones.

Type 525 San Francisco version SN 644

Type 525 San Francisco version - interior

photo above: Type 525 Saint Louis version - the switch between the filament dials is not original. It switches B+ on or off. 

Miscellaneous Information on Kennedy Receivers & Amplifiers

1. Nickel-plated binding posts are used on most of the San Francisco production
2. Plate Potentiometer circuit is included in early San Francisco production
3. General Radio and Paragon tube sockets used in early San Francisco production
4. Knobs are hand-made in early San Francisco production
5. Secondary coil terminals located on back of coil assembly
6. Position of phone jacks on 525 amplifier lower part of panel on San Francisco production
7. Bakelite capped binding posts used in most of St. Louis production
8.. Knobs are molded pieces in St. Louis production
9. Tube socket is a Kennedy marked piece in St. Louis production
10. Plate Potentiometer eliminated in St. Louis production
11. Series-Parallel switch moved from center-left panel to near primary condenser in St. Louis production on the Universal Receiver
12. Size of tube viewing ports reduced in St. Louis production
13. Serial numbers eliminated from the front panels in late St. Louis production - serial numbers are then on metal tags inside cabinets
14. Additional pot sometimes added to filament circuit to allow easy use of .25A tubes - I have seen this on several different Kennedy receivers. The workmanship is usually very good leading one to believe the work could be factory. Dealer installation on earlier receivers also a possibility.
15. Position of phone jacks on 525 amplifier center of panel on St. Louis production

Restoring and Operating Kennedy Receivers Today

Front Panel Care - Even though the formica panels look indestructible, they are somewhat delicate. Don't use any kind of abrasive polishing compound on the panel. If the panel looks "spotted" or "dull" and you polish it with abrasive compound, the "spotting" will get worse. This is because the actual high-polish skin of the formica is very thin and with age, exposure to excessive moisture or excessive polishing, the material under the skin begins to show through. More polishing only thins the skin so that more "spotting" develops. About the only thing that can be done is to apply Carnauba wax since it is non-abrasive. If the front panel is in excellent condition with no spotting or dull spots, don't do anything to it other than to wipe it carefully with a clean soft cotton cloth to remove dust.

Cabinet Restoration - The original finish was shellac, so it is somewhat delicate compared to modern finishes but at the time the Kennedy receivers were new, shellac was a common finish found on many types of furniture. Shellac will do odd things though and an "alligator" look, checking or wrinkling comes from constant exposure to widely varying temperatures found in poor storage conditions. If the finish is really bad, "Amalgamator" (available from Mohawk) will usually correct the problem. Amalgamator is a mixture of denatured alcohol, lacquer thinner and a few other chemicals. It is brushed on the finish where it then dissolves it and then, as it dries, allows the finish to set up again, usually looking better than it did before the application. If a total refinish is necessary, then shellac should be used. Most shellac used at that time was Amber Shellac which has an orange-brown color to it.

Matte Silver Dials - Handle these dials with care as the matte silver plate is extremely delicate. Don't use any abrasives, don't aggressively clean or use any scrubbing action, don't use Windex. Just about everything that we normally use for cleaning seems to degrade the finish on these dials. I have soaked them in warm soapy water (dish soap) for an hour with no adverse reactions. I gently dry the dials with a cotton cloth - no paper towels. This is about as aggressive as I would get cleaning the matte silver plating. At one time, Roland Matson refinished these dials in the correct manner but Roland is now long gone. Available on the web are several rub-on silver plating concoctions but whether they end up looking correct is unknown. Many of the silver plating solutions use cyanide in the mixture, so I think it's probably best to just leave the dials original.

Type 281 Dial Restoration - These dials seem to take a beating too. I have tried thinly painting the dials and then applying a silver paint fill but the results were less than satisfactory. The black has to be very, very thin. What does work is to use black "patina" - a chemical dye that is usually available at "Stained Glass" shops. They use it for dying the solder over the copper strips used in making leaded glass items. The "patina" will dye the dial metal (brass) black. Then the silver fill can be added and it will look correct. After the paint dries, the dial can be given a coat of clear lacquer. The original dial finish was somewhat glossy.

Operating the Kennedy Receivers with a 201A - The Kennedy regenerative receivers will function fine using a thoriated-tungsten filament 201A type tube. This type of tube operates at approximately 5vdc at about .25A, or about 75% less current than the pure-tungsten filament 200 and 201 tubes. Since much less current is drawn with the 201A tubes, the amount of filament resistance needed to drop approximately 1vdc is much higher (assuming 6vdc A supply and using the filament control to adjust the tube filament to 4.5 to 5.0vdc.) Fortunately, the value of the Filament Control potentiometer in the receivers is usually high enough that it is possible to use a 201A (with a fixed 6.0vdc A supply) and have adjustability from 4.7vdc and up. It is additionally helpful if the A supply is itself adjustable which will then allow setting the A voltage to a level that allows an ideal range of adjustment using the Filament control. When using a 201A for a detector you will have to increase the detector plate voltage to +45vdc for best performance. Using a 201A tube results in just about the same level of sensitivity as using a very good emission 200 tube. You will find that more tuning care is necessary when the receiver is operating as an autodyne (oscillating) detector since the range of adjustability in much narrower and the detector will drop out of oscillation frequently. When operating as a standard regenerative detector virtually no difference will be noted using the 201A as the detector.

Requirements for Operating the Kennedy Receivers & 525/521 Amplifier - The Kennedy receivers and audio amplifiers require several accessories for good performance. They are:
   1. Adjustable Power supply capable of 4.5 to 6vdc at minimum 4A for the A supply (well filtered)
   2. Power supply capable of +22vdc and +60 to +90vdc, minimal current required ~30mA (well filtered)
   3. Antenna, end-fed wire 75 to 200 feet long and as high as practical
   4. Real Earth connection. Ground rods and radial system work best. House ground works fair to poor.
   5. Baldwin earphones or other Hi-Z phones, Horn Speaker (Hi-Z vintage type)
   6. A good set of tubes with good emission, one UV-200 and two UV-201 (201A tubes can be used)

Operating the Kennedy Universal Receiver Today
 

photo above: The Kennedy Universal Type 110 Receiver with the Type 525 Two-Stage Audio Amplifier set-up and in operation (note 4.2vdc indicated on the Type 110's panel voltmeter.) The Type 110 is tuned to Reno-Tahoe Int'l AP NDB "NO" on 351kc, as indicated on the digital frequency counter. A Digital Frequency Counter can be used for an accurate tuned frequency readout since the Type 110 is operated as an Autodyne detector when tuning in NDBs. This operation has the detector oscillating at the tuned frequency. The oscillation can be coupled to the frequency counter by wrapping a few turns of wire around the antenna lead. You will have to readjust the Regeneration higher for the correct readout because the counter will respond to noise, signal modulation and other interferences causing a somewhat erratic reading. By increasing the Regeneration, the signal is reduced and the display will become steady. After the frequency is noted then readjust the Regeneration for maximum sensitivity.

Certainly, the Kennedy Universal Receiver was built to a high quality standard but does that high quality result in excellent performance? By reading the original manual for the St. Louis version of the Universal Receiver, one gets the impression that the receiver is mainly intended as a Broadcast receiver. All of the Kennedy receivers are excellent AM Broadcast receivers. However, most AM Broadcast stations today are so powerful that they can be tuned in with a crystal set, so tuning around there doesn't really test the Universal's capabilities, even though that may have been its main intended use. Just below the AM Broadcast band is where the Airport Non-Directional Beacons are located. From 195kc up to 529kc is where all the NDBs can be found. Their only transmission is to send their station ID in MCW every few seconds. Most USA NDBs run 25 watts to various kinds of antennae. Regional and Coastal NDBs run from 100 watts up to 2KW for transoceanic beacons. Canadian NDBs also run substantially more power than USA marker beacons (25W.) The hams of the early twenties were mostly using  rotary gap, damped-wave spark transmitters, which were essentially sending a MCW signal. The MCW signals from NDBs would probably represent a decent test signal, especially considering the low power that most of the transmitters run.

The Set-up - I used the Kennedy Universal Type 110, SN 5403, an all-original example of the receiver, along with a 525 Two-Stage Audio amplifier, also a St. Louis version with replacement audio interstage transformers but otherwise original. Audio output was to a pair of Baldwin Type C earphones. Power was provided by a Lambda 6vdc 4A power supply for the A supply. An RCA Duo-Rectron provided the B+ voltages of +22.5vdc for the detector and +90vdc for the amplifier plates (+90vdc works much better than the +60 recommended in the manual.) The Duo-Rectron is a mid-twenties B eliminator that uses an 874 regulator tube so the B+ voltages remain constant regardless of load changes. Tubes used were RCA UV-200 detector and two RCA UV-201 amplifiers. The antenna was my ham antenna, a 135' tuned dipole with the feedline tied together. This theoretically provides a vertical antenna with a large capacity hat, something like the "T" antennas used in the twenties. The earth ground used was the ham station ground which uses two different ground rods and interconnecting buried wires.

Operating as an Autodyne Detector for NDB Reception - This method of operation allows the Universal to tune in NBD signals. It is much easier to find NDBs if you can hear their carrier signal. When operated in the oscillating mode (autodyne) the detector acts as both a detector and an oscillator that is oscillating at the tuned frequency. This provides a heterodyne action and allows the operator to hear the carrier on modulated signals. Additionally, when operated as an autodyne detector the sensitivity is increased substantially, further enhancing the ability to find weak NDB signals. When oscillating, all of the controls will interact so the best procedure is to first tune the receiver to the approximate frequency where NDBs are transmitting, about 350kc is a good place to start. Set the Primary Inductance to 4 tuned in Series and the Secondary Inductance to 3. Set Filaments as for AM BC reception. Set the Secondary Condenser to about "10." Tune the Regeneration until a 'click' is heard, or you hear a hiss in the 'phones, either indicate that the detector is oscillating. This is usually about 5 on the Regeneration. Tune with the Secondary Condenser until you hear a heterodyne indicating a carrier is being received. When you tune the Primary Condenser for maximum you will find that you hear a 'click' at resonance. This is an indication that the Coupling is too tight. Reduce the Coupling control until when tuning through Primary Condenser resonance, the 'click' is no longer heard. This is the "Critical Coupling" setting. It is dependent on many things but the most influence is from the setting of the Regeneration. However, leave the Regeneration alone for the moment and use the Secondary and Primary Condensers to tune in the signal to maximum. Then fine tune the Regeneration for best sensitivity. The signal should be tuned to zero beat and then the CW ID can be copied. This setting of Regeneration and Coupling will be good for 20 or 30kc before you have to "touch-up" the setting the Regeneration. In tuning NDB stations, use only the Secondary Condenser, then tune to maximum with the Primary Condenser and adjust the Regeneration as necessary.

The Hand Capacitance Problem - When operated as an oscillating detector all controls interact because much of the circuitry is actually radiating em fields. Normally, autodyne/regenerative detector receivers are very well shielded. Many have all metal construction and early ones, like the SE-1420, have complete shielding utilizing inner panel shields and complete cabinet shields. Looking inside any of the Kennedy receivers one will note a complete lack of shielding. This results in each control having an associated em field around it and its knob or dial. When the operator's hand is on the control, the hand adds a certain amount of capacitance to ground near that particular component. This hand capacitance detunes the receiver and when the hand is removed, the capacitance changes and the receiver jumps a few kilocycles to a slightly higher frequency. All of this makes any of the Kennedy receivers difficult to operate as autodynes. If the operator practices awhile with the receiver in oscillation, he will get used to the hand capacity effect and will begin to compensate for it while tuning. It's a hassle but it can be done.

More on the Hand Capacitance Problem - Why such high quality receivers, that were obviously intended for some of the commercial users, would have been built with a complete disregard for the hand capacitance effect is a mystery. The cost of adding the necessary shielding would have been minimal, therefore some other reason must have influenced the decision to not install shielding. Perhaps, Kennedy intended their receivers to be primarily for Broadcast and Radiophone reception where, when operated as a straight regenerative receiver, the hand capacity effect is negligible. Other signals considered may have been those from the hams that were running rotary gap, damped-wave transmitters, a modulated signal that would also be tuned with a straight regenerative set up. The only transmissions in the twenties that would have required autodyne operation (because they were un-modulated) would have been those from Arc transmitters. Arc transmitter were used almost exclusively by the Navy. Also signals from Alexanderson Alternators are CW and again mostly operated by the Navy. Then there were the hams that were using tube-type CW transmitters but in 1921 they were few in number. So, maybe Kennedy designed their receivers for the most popular modes of transmission and felt that autodyne operation would have only been used casually so the problem of hand capacity effect on tuning was not going to be an issue.

   338kc - PBT - Proberta, Red Bluff, CA                 368kc - SIR - Sinclair, WY
   338kc - RYN - Tuscon, AZ                                   371kc - TVY - Tooele, UT
   332kc - LBH - Portland, OR                                 383kc - PI - Tyhee, ID
   335kc - CC - Buchanan AF, Concord,CA             385kc - WL - Williams Lake, BC, CAN
   329kc - TAD - Trinidad, CO                                 389kc - YWB - West Bank, BC, CAN
   344kc - FCH - Fresno,CA                                    380kc - BBD - Brady, TX
   350kc - NY - Enderby, BC, CAN                         395kc - ULS - Ulysses, KS
   351kc - NO - Reno, NV                                        400kc - QQ - Comox, Van.Is.,BC, CAN
   359kc - BO - Boise, ID                                          404kc - MOG - Montegue, CA
   356kc - MEF - Medford, OR                                 408kc - MW - Moses Lake, WA
   368kc - ZP - Queen Charlotte Is,BC,CAN             414kc - LYI - Libby, MT
   367kc - SX - Cranbrook, BC, CAN                       411kc - RD - Redmond, OR
   371kc - ITU - Great Falls, MT

LFA - 347kc - Klamath Falls, OR
CVP - 335kc - St. Helena, MT
DC - 326kc - Princeton, BC, CAN
ONO - 305kc - Ontario, OR
YYF - 290kc - Penticton, BC, CAN
XC - 242kc - Cranbrook, BC, CAN
GLS - 206kc - Galveston, TX
AEC - 209kc - Base Camp, NV
SF - 379kc - SF Int'l AP, SF, CA

Kennedy Receivers in the Laboratory

Dr. Royal Rife's Kennedy Radio Equipment

 In the 1920s, Dr. Royal R. Rife began experimenting with the possibility that disease causing micro-organisms could be destroyed by exposing them to specific RF frequencies driving a multistage amplifier to power a high voltage-gas filled ray tube. Most of the early work was carried out using Kennedy receiving equipment as the RF frequency generators. This can be accomplished by setting up the regenerative receiver in an oscillating condition and then coupling the desired output from the Antenna Input post. When the detector is oscillating, those oscillations are coupled into the Primary Tuner and then coupled onto the antenna. The oscillations can be a relatively high amplitude and are at the frequency that the receiver is tuned to. By using the Antenna Input post as the "Oscillator Output" the regenerative receiver can be used as a variable frequency oscillator. Frequency is controlled by the Secondary Condenser control and amplitude can be adjusted by either the Regeneration control or the Coupling control. Later, Dr. Rife was interested in the effects of modulated waveforms and used one receiver operating as an oscillator to modulate a second receiver also operating as an oscillator. This was accomplished by connecting the "carrier" oscillator-receiver's Antenna post to the Ground post of the 'modulator" oscillator-receiver and then taking the modulated waveform from the modulator-receiver's Antenna post. Whether using single waveform or a modulated waveform, Dr. Rife would then route the signal into a five stage amplifier to boost the output enough to drive a high voltage, helium gas-filled ray tube. The effects of the RF exposure on various micro-organisms from this setup were monitored in Dr. Rife's elaborate optical UV microscope (center on the bench.)

 photo left: A vintage photo of Dr. Rife's laboratory showing the Kennedy 110/525 and 281 equipment (left,) and his elaborate UV microscope (center.)

Recreating Dr. Royal Rife's Multiple Frequency Generator

Our "Kennedy-Oscillator" experiment was requested by two well-known researchers on Dr. Rife's early work, Jeff Garff and Jason Ringas (Rife Research Institute.) The goal of the experiment was to show that such a setup as shown in vintage photos of Rife's laboratory would indeed produce the desired waveforms. We used our SF Kennedy 110 Universal receiver with its SF Kennedy 525 amplifier and our SL Kennedy 281 Shortwave receiver as the generators. We powered the receivers using various power supplies to provide the 6 vdc at 3 amps required for the 110/525 combination and the 6 vdc at 1 amp required for the 281. Separate B+ supplies provided +20 vdc for the detectors in each receiver and the +60 vdc required for the plates in the amplifier. Each receiver and the amplifier were set up using the pure tungsten filament tubes of the time, UV-200 soft detectors and UV-201 hard amplifiers. Rife listened to the receiver output with earphones - probably to verify that each receiver was oscillating and to monitor any unexpected changes in his adjustments. We did the same. We measured frequency, amplitude and harmonic content with modern equipment, e.g. spectrum analyzer, oscilloscope, digital frequency counters, etc. Stability of the setup and the waveform output was surprisingly good. The repeat ability and accuracy were excellent, output was very high and the sine waves generated were free from distortion and harmonic content. Our conclusion was though it seemed unlikely that the Kennedy set up would be accurate or stable, just the opposite was true - it was fairly easy to duplicate the frequency generation part of Rife's experiments using early Kennedy equipment and the results were surprisingly good.

Henry Rogers - June 11, 2007

photo left: The Kennedy 281 (top) and Kennedy 110/525 (bottom) set up with Lambda power supplies for the filaments and a homebrew eliminator for B+ requirements. The GR freq. counter is monitoring the 250kc signal from the Kennedy 110.