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(16pages) Index: Chinese Type 139 A Radio Receiver; by Bill Howard TWO VERY RARE JAPANESE RADIO SETS; The Type 97 Light Wireless, & Mark 66 Wireless Sets, by Bill Howard JAPANESE HRO TYPE RADIO RECEIVERS; By: LTC William L. Howard MEMBERS WRITE; More on Axis HRO's. from Hue Miller CHINESE 702 SERIES RADIOS; By: LTC William L. Howard *********************************************** Chinese Type 139 A Radio Receiver; by Bill Howard General description of the set. The Chinese Type 139 A Radio Receiver is also late Vietnam war, if in fact it was part of the conflict. It is probably the replacement for the Type 139 Radio Receiver which was a tube set and was powered by a 90 volt dry cell and 1.5 volt dry cells. As of September 1968, none of the R 139A sets had been captured by US forces to the best of my knowledge. This particular set had a serial number of 70 1917. It was speculated that it was made in 1970 and was really set number 1917. This has not been confirmed by any source. If in fact it was made in 1970, it would have entered the Vietnam Conflict in 1971 or 1972, just as the U.S was pulling out and the Techjnical Intelligence effort ceased to function. Physical Description : The set is 10 inches wide, 3 and 1/2 inches deep and 5 inches high.The battery box and four rubber feet add another two inches to the set, making the overall height 7 inches. The weight, with out batteries is approximatly___ lbs, more with all 7 batteries in place. There are sling swivels on either side, indicating that it was designed to be carried over the shoulder, similar to a Ladies handbag. Spring loaded snap catches (4) hold the front panel cover on the set. An additional; four snap catches hold the battery box on the bottom. The battery box is hinged and can not be completly separated from the radio. This set is all solid state and is powered by 7 D cells, providing 9 volts and 1 1/2 volts. The radio is removed from the case by unscrewing four captive screws and then sliding the radio out of the case. Difficult to do as there are no real handles, only one knob for pulling. The set tends to stick to the rubber gasket and the power plug is a tight fit in the connecting socket. This is probably due to age. Once out of the case, there is an extension of the power cable and plug which plugs into the set and allows it to be used with the batteries in the battery case while the set is being worked on. This was no doubt inspired from looking at the Japanese radios of WW II. There are provisions on the front and the side for a pair of headphones to be used. The plug sockets are smaller than the standard 1/4 inche and larger than the standard min plugs available in the USA, which means the original headphones must be obtained or a means of rewiring developed for use with US style plugs. The headphone jack on the side panel is encased in a plastic shield which makes the set water tight. It also makes re-wiring almost impossiblewith out damaging the seals. Front Panel Controls: On the bottom laft are three controls. The far left control is marked in Chinese and has the number 0 in the center. It is connected to a potentiometer. The center control indicated volume. Turning it clockwise increases the volume. It too was a potentiometer. The control on the right rotates through 360 degrees but has markings on the case through 180 degrees. It is connected to a small variable capacitor and is probably for adjusting the antenna. Above these controls is the main tuning control. It has a screw down clamp to hold the dial fast however this did not seem to be working. Above this control are two smaller controls which are connected to switches. They are 3/8 inch in diameter and not that easy to turn. One switch is connected to the dial light and derives power from the 1 1/2 volt battery.(On this set, the dial light was burned out) To the right is the main tuning dial and window. The window is lighted, as mentioned. Three scales are visible in the window. On the upper right side is a 3 position switch marked 1, 2 and 3 which is probably the band switch. Below this is another control, a 5 position rotary switch. This seems to be a sort of function control, Off and whatever else. Below this is one of the two jacks for the head phone connection. Two more items are on the front panel, screw terminals with the symbols for antenna and ground. Another screw terminal is located on the top of the set. At first I thought it might be for an antenna connection for when the set was installed in a vehicle. It was not, however, connected electrically to either the ground or the antenna terminal. A second jack socket was located on the side which was for a second set of headphones. Interior Construction: The set is modular in construction and is made up of circuit boards which can be replaced if one is found to be defective. All controls are mounted on the front panel and the modules are mounted on a metal frame, similar to the Japanese sets of WW II. Were it not for the transistors, one would think one was looking at a late war Japanese set. The center area of the set contains the three gang tuning capacitor. A worm gear meshes with a gear that turns the capacitor. At the other end is another gear train which turns the tuning dial. Very rugged construction and probably capable of withstanding rough handling. There are three tuning modules mounted on top of the set. Another control, the band selector switch, is mechanically linked to three rotary switches, one per tuning module. Each of the three modules had three coils, the rotary switches and assorted capacitors, resistors and other items, believed to be capacitors, which appeared to be adjustable through access ports on the top of the module covers. These appeared to have been set at the factory and were not really designed for field repairmen to work on. There are two other modules, one on the side which had three IF transformers but were not adjustable as the tops had been sealed with solder at the factory. This module also had a plug in crystal which was marked 500 KHZ. There were three transistors, 10 capacitors and 23 resistors. The capacitors were in metal cans and were the PC board mountig type. The resistors were 1/4 watt resistors. There were two other items, both in metal cans, one of which had two leads so I assume was a capacitor. This module was electrically connected to the potentiometer on the front panel which was also connected to ground. The second module was on the bottom and had two interstage transformers, 15 capacitors that I could see, at least one transistor and numerous resistors. This module was in such a position that the parts could not easily be seen. There were at least 6 resistors. There was evidence of corrosion on some of the parts. Most of the capacitors had insulated sleeves over them to shield them from one another. The final component was a square metal can that plugged in to a socket. Contact was made by two screws that fit into sockets. This did not seem to be the best method of plugging something in but presumably it worked. Operating Characteristics: The tuning dial was graduated in three scales, one from 1.5 to 3.6, the second from 3.6 to 8.5 and the third from 8.5 to 18.0. I assume these are megacycles Other characteristics are not currently available. Tactical Employment: The Chinese military is not as dependent on radio communication as the American army is. In many cases, the subordinate units have a receiver only so they can listen for instructions but can not ask questions. This set can be used in a weather warning role as well as listening for coded messages. Strengths and weaknesses: Principle strength of the set is itĚs compact size, rugged construction and itĚs ability to run on flash light D cells, found in most every hardware store. Major weakness is the fact that it is not easily repaired. Removal of either of the two lower modules would require considerable labor. Replacement of one or more of the tuning modules would require removal of all three so that the shaft for the rotary switches can be withdrawn. It is my opinion that this set is basically a throw away set. If anything breaks down, throw it away and get a new one. Collector Value Difficult to place a value on this set. It is not readily identifible as part of the North Vietnamese or Viet Cong arsenal during the period of the U.S. effort during the Vietnam War. Probably worth about $150 to $200.00 to a serious collector. Would be worth more if the headset were included as well as antenna, technical manual and a schematic. An interesting piece of Radio History of the Chinese Armed Forces. It is also one of the first Chinese military sets to use transistors, a step forward for the Chinese Radio industry THE WILLIAM L. HOWARD ORDNANCE TECHNICAL INTELLIGENCE MUSEUM e-mail Telephone AC 813 585-7756 --------------------------------------------------------------------------- ed) Jane's 1988 does list the type 139, & 139B sets, but not the 139A. The Type 139B is described as tuning 1.5-18mc in 3 bands, AM/CW, and includes a xtal calibrator. Size is 192mmH x 278mmW x 102mmD, 3.8kg. All other parameters appear to be the same as Bill's description of the 139A. ****************************************** TWO VERY RARE JAPANESE RADIO SETS; The Type 97 Light Wireless, & Mark 66 Wireless Sets, by Bill Howard Japanese Mark 66 Wireless Set This set is a very rare set and seems to be a precursor to the other one man portable sets. This set was covered in TM 11-227A but there are no Captured Equipment Reports or Technical Bulletins. It must have been replaced by other sets and there were limited quantities in the field and it was felt that there was little need for a TB to show U.S. troops how to use it. The set is a battery powered walkie talkie type radio covering 2.5 to 4.5 MC. It is capable of voice and CW. It uses three UZ 109C double triodes. It is housed in a metal case and the batteries are contained in a box in a leather pack. The radio weight is given as 8.1 lbs and the battery box and pack are listed as 2.1 lbs. The set is compactly built in an 11 x 4 1/2 x 7 1/2 inch metal case, about the size of a school lunch box. Efforts have been made to waterproof it but no effort to tropicalize it. Controls do not lock, and the tuning dials are graduated 0 - 100 making reference charts necessary for tuning. The set is not of chassis construction, rather parts are mounted on the sides, top and internal brackets. Transmitter controls are on one side along with the socket for the crystal, the microphone and the external key. There is also an internal key, mounted under a waterprrof seal. Receiver controls are on the other side along with a socket for the power cord and headset. On the top are two meters and three lever switches which are used for transmit, the second for receive or frequency check and the third for telephone or telegraph operation. It was a very complex switching system. The sets components can be gotten to by opening the front cover. Some of the items can be easily gotten to such as tubes but any repair would require a considerable amount of work just to get to the components needing to be replaced. I was fortunate to get two of these sets, one almost complete. It had the microphone, the headset and the power cord. The second set had only the headset. The lever switch on the top of the one set was broken as they were very fragile. Both sets had a very loose front panel. and any thought of being waterproof was long gone. While the rubber gasket was intact, it had shrunk due to age. The isenglass cover for the tuning charts and schematic had yellowed with age but was still there and in reasonably good condition. The accessories for this set are the battery box, battery box pack, headphones, microphone, antenna and counterpoise rods and the power cable. The photograph in the TM shows a small pouch sitting on top, about the size of the front ammo pouch which I assume held the key and other accessories. I have only seen two of these sets and have never seen the battery box or pack. It is my opinion that this set predates the Type 94-6 set and the Type 97 Light wireless set. Both of these sets corrected the deficiencies in this set. The Type 97 Light Wireless Set This set closely resembles the case for the Mark 66 set but there the resemblance ends. The Type 97 Light Wireless set was adopted by the Japanese Navy for the Naval Landing Forces. As a result they were made in limited quantities. There are however captured equipment reports done on this set as well as a Technical Bulletin so U.S. and allied troops could make use of the set if captured. The designation Type 97 would indicate that it was adopted three years after the Type 94 series. The accessories for this set are in many cases the same as for the Type 94-6 set. The same battery box and pack as used on the Type 94-6 is used with this set. The set is a one tube, a UZ 31 MC (Japanese Dual triode) AM set covering 23 to 31 MC. It is capable of voice, and tone transmission and reception. It is a plate modulated set with a Hartly oscillator for the transmitter and a super regenerative receiver. Power requirements are 2 volts for the filament and 120 volts for the plate. The output of the set is 20 milliwatts. It has a reported range of 1.5 miles. The set is different from prior man portable types in that it is designed for multiple power sources and also for much rougher handling conditions. While the MK 66 set and the Type 94-4 set have bakelite plugs for the headset/mike connectors and power cables, the Type 97 has metal plug in and screw down connectors. No chance they will be pulled loose. The set can be operated in the transmit or receive mode from the battery pack alone, unlike the Type 94-6 which required the generator to be cranked only for transmission, while the batteries power the receiver. The use of just a battery pack would be the ideal method for troops coming ashore under fire. Once ashore, and a beach head established, it can then be powered again in receive and transmit mode by use of the hand crank generator. This however requires changing the power cable. This would seem to be useful when there is no resupply of batteries but it requires a second man in the radio team to crank the generator, even during receiving. This man was probably a security force while coming ashore, a replacement if the principle operator was killed in the landing and possibly was the second shift radio operator for 24 hour operations. In addition, the set had an accessory called a secondary cell adapter. This allowed the radio to be powered from heavy duty rechargeable batteries. On the following pages are a line drawing of the radio and the generator, the schematic for the set and the circuits for transmit and receive, and the circuit diagram of the Secondary cell adapter. This type set was captured by U.S. forces and evacuated to the Camp Coles Signal Laboratory in Bradley Beach, New Jersey (Part of the Fort Monmouth complex) where it was tested and Captured Enemy Equipment Report No 60 was prepared. The set then became the subject of Technical Bulletin TB Sig E 18, issued in November 1944. Combat employment history is very sketchy. The only photograph that I have seen of this set in use was in the book by Shigeo.Sugawa dealing the the Japanese forces in China. Titled JAPANESE SOLDIERS AT THE CHINA FRONT 1930ĚS. Page 100 shows a picture take on Hainan Island February 14, 1938 showing specialists from the Communications Division of the Uta Company from Kure, Hiroshima Prefecture setting up a field communication post. Shown in the picture are the TM Handy Wireless set, a suitcase type radio and in the background is a soldier with a Type 97 Light Wireless set. On page 131 there is another picture of a Navy Communications Squad on a Gunboat. The picture, taken on September 10, 1940 on A Roke Lake in Jiangsu, Central China, clearly shows three soldiers equipped with the Type 97 Light Wireless Set. A fourth man is shown in the background and he also has the same radio set. Very little is said about the radios as the authorĚs expertise is in weapons, uniforms and equipment. The closest U.S. type set to these sets was the SCR-195 and while somewhat heaver was certainly more compact, less cumbersome to transport and use. While the SCR-195 was 1930Ěs technology, it was quickly replaced by the BC-611 and the BC-1000 sets, The Japanese, on the other hand, stuck with these sets through the entire war. THE WILLIAM L. HOWARD ORDNANCE TECHNICAL INTELLIGENCE MUSEUM e-mail Telephone AC 813 585-7756 ****************************************** JAPANESE HRO TYPE RADIO RECEIVERS; By: LTC William L. Howard 1934 the National Company came out with a new radio designated as the HRO, supposedly for "Hurried Rush Order". This set was a 9 tube superhetrodyne set that used plug-in coils in the front panel, and an unusual four gang tuning condensor that was mounted at right angles to the worm gear attached to the tuning control. The tuning dial also had windows that revealed dial graduations. This set was copied by many nations, if not directly, then in a similar style, plug-in rectangular coils, four gang tuning condensor. Figure 1 Schematic of Type HRO receiver. By the late 1930s the Japanese realized that new radios were needed and by 1943 these sets began to appear in the field. For the most part, Aircraft radios began to be made using octal base tubes. Examples include a radio direction finder that was copied from a pre-war Bendix Aviation set. Other aircraft radios began to use octal base tubes. The first of the Japanese HRO sets was an exact copy of the HRO with some minor changes. Once the factories were tooled to produce parts for this set, it would appear that radio engineers were instructed to design furure radios making use of the components that were made for the HRO. Principaly these were the plug in coil forms and the four gang tuning condensor. The first set of the HRO copies was designated as the Mark 1 Ground Wireless Receiver. It came in a large wooden chest that housed the receiver, a power supply, two drawers of plug-in coils and a drawer of accessories. These accessories included the headphones and another set of IF transformers as well as other items. The power supply contained two switches and a meter. This set was followed by a Mark 2 Wireless Ground receiver. I have not seen any of these so am unable to comment in detail on this set. This set seems to have been issued with a companion transmitter. It used eight tubes, a UZ6D6, a Ut 6l7G,another UZ6D6, two UY 76s,two Ut6B7/2 and a UZ 41 as the final audio amplifier. This set seems to have followed the schematic of the HRO but with out the amplifier tube for a speaker. Figure 2 Block Diagram of Mark 2 Wireless Set Receiver. The Type 99 series of aircraft radios had progressed from the Mark 1 to the Mark 4. The Mark 5 series had a receiver that appears to have been strongly influenced by the HRO design. This set made use of five tubes while the National HRO had 9 tubes. A 6F7 and four UZ 78s were mounted behind the ganged tuning condensor, and behind the row of tubes were the interstage transformers. Since the aircraft did not need a speaker, the last tube in the HRO schematic could easily be eliminated. Other modifications could have been the elimination of one of the IF stages and possibly one stage of RF amplification, although the four gang condensor would indicate two stages of RF amplification. The next set in the HRO series that I have encountered was called the Mark 3 Ground Receiver. Little information on this set exists. Someone sent me a polaroid photo of this set. By checking in a post war Japanese book on radios, it was identified as the Mark 3 Ground set. It appears to have been developed by the same group that developed the Type 99 Mark 5 receiver. The set was mounted in a metal case that had two elements below the receiver. What these were is not certain but was probably the power supply. It appears to have been the same power supply as used in the Mark 1 set but without the meter. By 1943 the Germans had begun to eliminate meters from their sets as parts were in short supply and it can be assumed that the Japanese experience was similar. Meters were needed for transmitter and not for power supplies. The Mark 3 set used the four gang tuning capacitor and a plug in coil. It however used only five tubes. A UZ 6D6, a Ut 6A7, and three more tubes, UZ 78 or UZ 6D6 which appear to have been interchangeable. Figure 3 Block Diagram of Mark 3 Wireless Receiver. There was also a companion transmitter with this set. It had three meters across the top, three vernier tuning dials, a plug in crystal socket and other controls. This transmitter appears to have been a four tube transmitter. The Japanese text refers to an 807A so it is assumed that all the tubes were 807As. Probably some sort of MOPA circuit. I have never seen one of these transmitters so the information is limited. The Mark 3 Wireless set set seems to have been superceded by a new ground radio designated WIRELESS STATION MARK 4 GROUND. Exactly what this set was designed for is uncertain, but the data plates on both the transmitter and the receiver had been stamped with a star emblem that was usually associated with civilians attached to the army. It is possible that this set was designed for use by homeland defense forces. The data plates were made to have the date of manufacture stamped on them but on the examples I saw, this date stamping was missing. This set had a receiver that resembled the HRO. It used a rectangular plug in coil on the front panel. According to information supplied by Takashi Doi, there was an early model and a later model of the Mark 3 sets. In addition a photograph in a post war Japanese book identifies the receiver and transmitter as the MU 23 set. MU is the Japanese abbreviation for MUSEN which means radio or wireless. Photographs on the next few pages show the Mark 3 and Mark 4 sets. The Mark 4 set probably was closer to the National HRO as it had 9 tubes, however the tuning capacitor only had three gangs and the coil box had three coil units. The IF transformer was mounted in a plug-in container so it is assumed that the requirement to change IF transformers when switching bands still existed. It can be assumed that there was also an accessory container for this set which housed the other coils, headphones, keys, cables etc. This set used UZ 6D6 tubes throughout. The 6D6 tube is a 6 pin tube with a grid cap. The five tubes mounted directly behind the tuning capacitor were protected by tube shields, the three tubes in the rear and one on the side were not encased in tube shields. The example that I saw had three plug-in coils. Coil Number 1 covered 4 MC to 6 MC, Coil Number 2 covered 6 MC to 9 MC and coil Number 3 covered 9 MC to 133 MC, a considerably wider range than the frequencies marked on the companion transmitter. Controls on the front panel of course were in Japanese but some one had penciled in BFO, Volume Control, Main tuning, Wave Tuning, High Cycle, and Antenna Decrease. Two other items were binding posts for Antenna and Ground connections. This receiver was designed to be connected to the companion transmitter. When removed from the case, there are two power ports, one four pin and one six pin. When I slid the receiver back into the case, the four pin socket was not exposed! It is therefore assumed that the four pin socket was to provide power when the set was out of the case and being worked on. Once back in the case, the set must be connected to the transmitter for power. The transmitter also has two power ports, both of which can be seen when the unit is in the case. The Six pin plug from the power source went to the transmitter and then a connecting cable transferred power to the receiver. The power port on the transmitter was marked with a red dot and the number 1 while the transfer ports on the transmitter and receiver were marked with a yellow dot and the number 2. While this set is easy to transport, it takes time to set the staion up and place it in operation. The transmitter for the Mark 4 Wireless set is shown on the pages following the photographs of the receiver. The entire station was designed to be carried in a canvas pack which is also shown. The example shown had two packs, presumably one for transmitter and receiver and one for the power supply and accessories. What sort of power supply was used with this station is unknown. Presumably a dynamotor or battery pack and generator were employed although it is possible that an AC Main line power supply was provided. As with other Japanese sets, all the parts are numbered and in the receiver, part number 1 is the antenna connector and the last numbered part is the headphone socket. In the transmitter, the reverse is usually the case with the key being number 1 and the higest number is the antenna connector. Part numbering facilitates following a schematic during repairs. While most tactical ground Japanese sets have a schematic mounted somewhere in the set, these sets had none. The HRO copy, Mark 1 set was also powered by a dynamotor. The dynamotor for use with this set is shown in the pages following the transmitter and receiver. In addition to the dynamotor, detailed photos of the power supply are shown. This power supply had provisions for input voltages as high as 500 Volts. By late 1943 or early 1944 the Japanese began to use octal tubes in the HRO sets. The set owned by Ken Lakin had what appeared to be factory installed octal tube sockets except for the oscillators. Changing these tubes to octal tubes would have required other major changes. Not being able to test these receivers and transmitters limits ones observations to the manufacturing process and to speculation on the reason for the design changes. Since the National HRO did not come out until 1934 it can be assumed that the Japanese did not get any samples until 1935 or 1936. As the Japanese Empire began to expand, especially to the far away islands, reliable long range communication was needed and the HRO was probably the best receiver of the time. Work was begun to copy the set and once tooling was made, there was a reluctance to re-tool, hence later versions tended to make use of parts that were already in production. As the war went on and the Japanese suffered defeats as well as a shortage of raw materials, manufacturing short-cuts were taken. This was most apparent in their rifles. Radios, on the other hand, were not something that readily led to manufacturing short cuts. The lack of a meter on the Mark 3 set's power supply was not a major change but rather an economy measure. The transition from a four gang tuning condensor to a three gang with a resultant shift from four coils to three coils, probably was a manufacturing short cut. It also shows that as the empire was collapsing, the range of communication decreased and perhaps one stage of RF was enough for the Japanese. Reducing the number of coils needed from the original 9 with the Mark 1 set to 3 coils for the Mark 4 set also reduced the amount of metal needed. The receivers turn up now and then but transmitters are rare items and the dynamotors are extremly scarce items as are the power supplies. Connecting cables and plugs are virtually non existant. Any effort to power up these receivers will require fabrication of plugs and cables. A power supply should also be built, if the original can not be found. Personally, I would not want to use the original power supply as too many things can go wrong. U.S. transformers, rectifiers and capacitors can be used to make a power supply that will work with out taking any chances on destroying the original power supply. Photograph Credits: Japanese HRO Set, Colin McKinnon, QST Magazine Japanese Type 99 Mark 5 receiver, Pat Lombardi Collection Photos by Pat Lombardi Japanese Ground Wireless Station Mark 4 transmitter and receiver, Lou Demers Collection, Photos by William L. Howard, Japanese Mark 1 Dynamotor, William L. Howard Collection Japanese HRO set and power supply, Ken Lakin Collection Photos by Janet Lakin Information on the National HRO and the Type HRO schematic were supplied by John Orahood. Schematic of the Mark 3 Set supplied by Takashi Doi, Yokohama, Japan. THE WILLIAM L. HOWARD ORDNANCE TECHNICAL INTELLIGENCE MUSEUM e-mail Telephone AC 813 585-7756 *********************************************** MEMBERS WRITE; More on Axis HRO's. from Hue Miller Re: HRO HRO = Hell of a Rush Order range of Nippon HRO coil not to 133 mc/s. that is of course way to high. also, Japan used a frequency-meter type dial, never duplicating the expensive National cyclometric dial. ( the German HROs by Seimens and Korting were built with National dials imported thru neutral Portugal. ) also, the Japanese "aircraft HRO" did not have 'local tuning', the capacitor was apparently only set up for flex cable tuning control. The 3-gang smaller, i call them "3/4 versions", were not necessarily war simplification, but entirely satisfactory for aircraft or field portable gear. The 'Chi Ichi' HRO was not necessarily a better receiver than the very heavy "special receiver 92" ( i think this is nomenclature ), but certainly smaller and probably easier to use, and repair. however, capture photos seem to show that even for farflung radio stations of the empire, the 'Special Receiver' type was the one in use, at least for shore stations, not the HRO. It's kind of an indicator of the level of Japan electronics, that the HRO seems to be among their most modern sets, when in the US and UK, the design was already showing its signs of age, being much less a modern radio than the Hammarlunds and Hallicrafters and the military models. The only advantage the HRO offered was mechanical simplicity, with no bandswitch, so less to fail; and it was also easier to repair. With the Japanese model, you also see problems apparent with other Japan communications equipment: light gauge metal cabinets, covers and such that are easily distorted and then no longer fit right. also, the coils on the Nippon HRO seem to use more of a thin blade type contact than the Allied sets, and this too seems less robust. btw, the '01' in Ground-Air Receiver 01, refers to 1941 design year, is that right? hue miller *********************************************** CHINESE 702 SERIES RADIOS; I first saw this radio in a display case at the Signal Corps Museum at Fort Monmouth back in the 1970Ěs. Supposedly captured in Vietnam, it was a set that I had not seen as of Sept 1968 when I left so I concluded that it must have entered service with the NVA after 1968. The set looked to be about the size of a carton of cigarettes, was displayed out of the case and did not have any accessories. I recently picked up two of these sets. One is labeled 702D and the other had no data plate but appeared to be an earlier version of the same set. I concluded that it must have been a 702, 702A,B,or C version. I will begin with a description of the set which I believe is the older set. The set comes in an aluminum case and is 10 Í long over-all, by 3 1/2 wide by 2 1/3 deep.The case has a steel D ring attached so it can be attached to a set of pack straps. The bottom of the set has two screws which must be removed, allowing the removal of the cover, which is then turned and allowed to follow the entire set as it is slid out of the case through the top. The radio is built on a heavy guage aluminum chassis that was stamped out of a sheet of aluminum. The chassis is fastened to the top 8 rivets. The top panel contains the antenna connector, a ceramic like socket to which an antenna is screwed in. There is a main tuning control which is a friction drive to the variable capacitor. The variable capacitor also has a dial with graduations which appear under a small window. There is also a push/pull switch which serves as an on/off switch. Below the top cover is the tuned circuit, consisting of a main variable capacitor with two stator plates and three rotor plates and two more much smaller air variable capacitors. One can be adjusted only after the set is removed from the case. The other small variable capacitor can be accessed from the out side of the case by a small screw driver. It is connected to the antenna. The coil is wound on a flat piece of clear plastic with a cross brace in the form of a X and the second part of the coil is wound on a circular piece of clear plastic mounted on top of the X form. The coil is 6 turns of 16 guage silver colored wire with the antenna coil being 4 turns of 22 guage wire. Above the coil is a press down switch which is accessable from the outside of the case. I assume it was for transmitting a code signal. Base on the fact that most Chinese Military sets operate between 2 to 12 MC, I conclude this set is in the same range. Below the elements of the tuned circuit, was the radio proper. The older of the two sets has RCA 3S4 tubes. There were two of these tubes mounted in sockets with metal spring loaded shields.From right to left, there were the one tube and a large paper capacitor, then a multi pole relay, then a potted transformer, the second tube and another paper capacitor and a final un-potted transformer. Below these or what might be called the underside of the chassis were resistors, capacitors and what I assumed to be an RF choke. The capacitors looked like the standard 1940 mica capacitors and or molded/paper capacitors. I counted four resistors, three of which were 1 watt size and one was a half watt size.There were five mica capacitors and one .05 MFD molded capacitor, which was made by the Sing Kee Condensor Works. These were either soldered directly to the tube sockets or to two terminal strips. The other two capacitors which were on top of the chassis were too difficult to examine for size and manufacturing specifications. Two rubber covered cables were wired to the circuit and fed out through the base to a power plug or the mike/headphone combinaton. The power cable terminated in a plug that was then plugged into a battery. The battery plug had been broken open, and three wires were then soldered to it, apparently in an effort to get power from a US battery of the required voltage. The other cable was connected to something that was missing. What appeared to be a mike with a push to talk switch was partially soldered on (one of three wires were soldered and the others were not connected to anything) The three wires to the mike were not rubber covered and appeared to be an attempt to make a field repair. The mike that was with the set, resembled an old style. The cover was held on by three screws. Removal of the cover revealed a badly deteriorated rubber gasket. Removing what was left of it, the mike appears to be a standard carbon telephone mike. Below this were to lever switches which were controlled by the PTT switch. The switch brought the mike into a circuit and the other switch probably operated the relay, RY 1. The three wires that came in did not appear to be field modifications or were a high quality soldering job. They were also braided so it is possible they came from the factory that way. It was my opinion that this was supposed to be both a receiver and transmitter. Pressing a PTT switch would activate the relay and Íre wireÎ the circuit. Most probably in the receive mode the one tube was a detector and the other an amplifier. In the transmit mode, one was the oscillator and the other the modulator. Not having the accessories, a power source and with broken components, it was impossible to do more with the set. I assume that it was adequate for short range communications. It also had some problems and/or design flaws which were corrected in later versions. Numerous changes occured between the set described above and the 702 D version. The first and most obvious change was the elimination of the hard wired battery and headset/mike cables. These were replaced by sockets and the battery cable must have had two plugs, one on each end. The mike/headset also had a plug. This change made it easier to remove the set from the case to work on. The open transformer was replaced by a potted transformer. I assume that they exhausted their supply of old style transformers while making the first radios and by the time of the D series, all transformers were potted. The area of the tuned circuit has been changed. The variable capacitor in the antenna circuit has been eliminated, as has the variable capacitor across the coil. The latter having been replaced by a smaller adjustable capacitor rather than the air variable of the older set. The main tuning capacitor remains the same. The tone transmitter switch has also been removed, thus making the outer case easier to manufacture. A small light bulb has been added to illuminate the tuning dial. Otherwise the tuning curcuit remains the same. A large coil has also been relocated from under the chassis to a position nearer the top of the set. The underside of the chassis has also been ÍstreamlinedÎ and all parts are easier to get to. There are 8 mica capacitors, still of the 1940 style but with numbers rather than a dot color code. and 10 resistors. RY 1, the relay has been changed. The older set had two contacts and the newer one has four contacts. In the newer set, the realay appears to be adjustable and there is a screw adjustment on the top. This appears to be a factory adjustment as the screw is painted fast. This set also had tubes of Chinese manufacture. Without having a technical manual, schematics or necessary accessories, it is not possible to do more than describe the sets and draw some general conclusions. These sets appear to have been inspired by the WW II BC 611 for size and intended purpose and the circuits inspired by the Japanese Type 94-6, only because of the use of two tubes and two transformers. This however is not a Japanese invention and the circuits or concepts were well known by the late 1930Ěs. The changes in the power cord and headset/mike appears to have been prompted by experience in the field. It may also reflect the fact that the cords and cables suffered damage in rough handling and that it was easer to supply new cables than to turn the set in to have the hard wired cables replaced. This set would appear to have been developed in the late 1950s and in use during the 1960s. By the 1970s transistors were coming into use and this set was phased out in favor of some ther radio. For itĚs time frame and intended use, the set appears to be adequate and up to the task. Operational testing may prove otherwise. William L. Howard LTC Armor USAR(Retd) THE WILLIAM L. HOWARD ORDNANCE TECHNICAL INTELLIGENCE MUSEUM e-mail Telephone AC 813 585-7756 *********************************************** (The preceding was a product of the"Military Collector Group Post", an international email magazine dedicated to the preservation of history and the equipment that made it. Unlimited circulation of this material is authorized so long as the proper credits to the original authors, and publisher are included. For more information conserning this group contact Dennis Starks at, ***********************************************

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