MILITARY COLLECTOR GROUP POST, April 29/98 INDEX: ANNOUNCEMENTS; COMMUNICATIONS EQUIPMENT OF THE NORTH VIETNAMESE ARMY, & VIET CONG; Part III, By LTC William L Howard MEMBERS WRITE; HUMOR; *********************************************** ANNOUNCEMENTS; Rain! I hate the stuff! Have received about 8" worth since Monday. Has made it impossible to even unload the old Power Wagon after the Little Rock trip, besides keeping me in a melancholy mood where all I want to do is nap in the recliner all day. Spring cleaning is at a complete stand still. PRC-6's, it is possible that a quantity of PRC-6's in good shape have been located, and might be available for a group purchase at $45.00. I'm working now to get this price reduced if we can generate enough interest, and purchase them all. Some new batteries are also reported to be available, and it may be that we can obtain these at the same time. Yes, I know that the PRC-6 is among the most common radios in the world, but we have a number of new, fledgling members out there that might not as yet own one. If you have an interest, let me know. Dennis *********************************************** COMMUNICATIONS EQUIPMENT OF THE NORTH VIETNAMESE ARMY, & VIET CONG; Part III, By LTC William L Howard The Viet Cong Home Brew sets There are at least three “home brew” radios known to exist. The first was shown in the July 1967 T.I.B. and was a transmitter and receiver built into a chassis that fitted into a Cal. .50 ammunition can. Very little effort was given to an analysis of this set. The voltages, the frequency range and power requirements were about all that was listed. One of my projects was to build a copy of the set. I ended up with the standard 6L6 transmitter circuit, but with a different 1.5 volt filament tube, using a coil wound on a section of cardboard tube with taps that fed to an octal tube socket. Changing the jumper wire in the socket changed the number of turns in the plate coil, as must have been done on the original. The set was tested by Jim Kearman at the time he worked for the ARRL and it worked. The receiver was a two tube set with a 1S5 detector and a 1T4 for an amplifier. When all else fails to get a radio working, I send it to Don Dean in Sarasota and he managed to get it working for me. The original set has been lost so it can not be studied in any detail. The second “Home Brew” set was built into a Cal .30 ammo can and is described in the following article, which was published in Electric Radio Magazine. VIET CONG HOME BUILT RADIO by LTC William L. Howard 219 Harborview Lane Largo, Florida 33770 In the early stages of the Vietnam conflict, the Viet Minh and later the Viet Cong were equipped with a variety of leftover WWII weapons supplemented by what they could fabricate in their underground factories. Communication equipment was also in short supply. This began to change and by 1967, the Viet Cong and North Vietnamese Army were equipped with sets made in China. The X06, copied in part from the US WW II SCR694, the Mercury Talk Set which resembled a WWII Japanese set and the Type 63 backpack set which looked like an AN/PRC-10 mounted in a BC-1000 were among the sets that were captured. Occasionally, a Soviet radio would show up but these were few and far between. Captured radio sets were first evacuated to the nearest Radio Research Unit, the local version if the N.S.A. and responsible for signal intercept operations where information of immediate intelligence value was recorded. Primarily this was frequency and range of the set. When Radio Research finished with the set it was evacuated to the Combined Material Exploitation Center (C.M.E.C.) for detailed technical intelligence exploitation. In most cases this resulted in the destruction of the set as all the components were removed and the remaining hulks were sent to the scrap yard. Samples of each set were placed in the C.M.E.C. museum and used for training new intelligence personnel. There were very few radios used by the Viet Cong, fewer captured by U.S. Forces and very few came back to the states in private hands. Today these sets are very scarce. In 1988, while a guest at the dedication of the new Foreign Material Intelligence Complex at Aberdeen Proving Ground, I went through the Ordnance Museum. The C.M.E.C. Museum in Vietnam had been evacuated and was now part of the Ordnance Museum. Many of the enemy weapons I had helped to evacuate were on display. One of the more unusual items was a Viet Cong "Home Brew" Radio built to fit into a standard U.S. 30 cal ammunition can.! took several photos through the glass case but these photos revealed very little other than subminiature tubes were used. Several years later through the efforts of Bill Seaby, the set was taken from the case and a set of detailed photographs was sent to me. The set was originally designed to be two radios on one chassis. Only one side was wired so it is open to speculation what the other side was to become. One part was a shielded variable capacitor, tube and coil. The remainder had four tube sockets, two variable capacitors and a large hole in the chassis, possibly for a coil. The side that was wired seemed to be a regenerative detector with three stages of audio amplification. There was one tube ahead of the detector which could have been an RF amplifier but there was no coil for such a stage. Subminiature sockets were used throughout the set. The coil for the receiver was wound on the base of an octal tube and an octal tube socket was mounted in the center of the chassis. Without any tubes in the set and a broken coil, the set was inoperable and simply a display item. Without being able to examine the set in detail, it was impossible to trace the wiring diagram but it appeared to be a regenerative detector with a capacitor coupled amplification system. The resistors went either to a bus bar wire or were grounded to the chassis. The final stage was connected to an output transformer which seemed to be for the purpose of isolating B+ from the chassis. The transformer output was grounded to the chassis and a red wire went to the headphone socket. I decided that t it would make an interesting project to duplicate this set and see if it could be made to work. The original set was made from a series of panels held together by brass machine screws. I obtained an ammunition can and began the process of making a cardboard chassis. Side panels, back panel and front panel were then cut from aluminum. The center panel and shields were also cut from aluminum. A template for the center panel was laid out, after all the parts were assembled and a second template was made for the front panel. Finding parts that duplicated the original set was difficult. Miniature 7 pin tube sockets of the same color as the original were finally located as were other parts. Then the main chassis and all panels were taken to a local metal working shop where holes and cutouts were done and the chassis was assembled. The tuning capacitor was mounted on the center divider panel and a local machine shop was contacted to turn a dial/drive pulley. Once the mechanical work was completed, the other components were mounted and the set began to take shape. The filaments were wired first, one lead to chassis and one lead to the main power switch. The chassis was A+ and B-. B+ was then wired to a bus bar wire and the output transformer was wired into the circuit. This set does not have a lot of room for wires and the lead to the headphone socket was buried under the other parts. The amplifier section was then wired. Resistors with proper values that resembled the original set were easy to find but capacitors were difficult. I used modern capacitors as I felt they were more reliable. The detector portion was then wired and coupled to the amplification stages through an RF choke. Since I could not find a circuit for an RF amplifier that did not use a coil, I decided to eliminate the first tube. The coil was wound on an octal tube base with a cardboard insert and plugged into the socket. The set was powered up and nothing happened! I had a local collector go over the set and we reached the conclusion the problem was in the detector circuit. After several further attempts to get the set operational I gave in and took the set to Don Dean in Sarasota who repairs old time radios. Don went over the set and finally got it to work. He rewired the coil and eliminated two stages of amplification. The end result was that a I S 5 tube was used for the detector and a 1T4 was used as an amplifier. In Sarasota, with a good antenna the set picked up 5 local AM Stations. In Largo it got three stations using a 30 foot copper wire antenna. The set now sits on the shelf as part of my Technical Intelligence Museum Displays. Several conclusions were reached as a result of this project. The first is that the set could have been made much smaller and still put in an ammo can and there would have been room for batteries, head set and antenna. The second conclusion was that it would have been easier to use a long strip of aluminum bent to shape than to have made it from separate panels. Of course, the Viet Cong may not have had a long strip of aluminum and were forced to use small scraps for the chassis. It is questionable if the original set ever saw service or was captured when U.S. Forces overran the underground factory. It is also possible that they could not get the original set to work which is why it was dropped and the other side was never wired. Shortly after this article was published in ELECTRIC RADIO Magazine, I received several letters with circuits for an RF amplifier that did not require a coil. Third confirmed Ammo Can Radio The third known “Home brew” set was shown in a photograph sent to me by Jan Schrader from the collection of photographs he brought home from Vietnam. The set was shown next to a crate of ammunition which looked like it was for a WW II Japanese howitzer. There was a Chinese howitzer that used the same caliber ammunition as the WW II Japanese gun. I assume that the radio was made in the 1950’s or early 1960s and captured very early in the war. It was not mentioned in the 1967 T.I. B. This radio set has disappeared and all that remains of it is the photograph. No effort has been made to make a reproduction of the set. Several More “Almost Rans” The first set which I call an “Almost ran” set started as an attempt in 1988 to reconstruct a VC ammo can radio that I saw on display at the Ordnance Museum. Photographed from out side the display case, I could not tell very much but knew what the top panel controls were and saw 7 pin miniature tube sockets. I obtained an ammo can at a local surplus store. I then made up a cardboard model of what was wanted and drew in the diagram of all the parts. I then contacted a machine shop to fabricate a chassis, and drill holes for tube sockets. Once this was completed, I took it home and began to mount the components. I had to rig up some form of pulley arrangement to get the dial drive to turn the receiver tuning capacitor. I divided the set into a receiver section and a transmitter section. At this time my knowledge of radio circuits was limited and I took the set to Craig Smith and asked him to “wire it so it looked good”. The set then sat on the shelf with no further work being done on it other than to make a battery pack for it that looked reasonable. I then decided that I would make up some accessories for it. An antenna holder was made from hardware store nuts and bolts, scrap wood and some sections of a bamboo rod. Next came a similar set up for the ground contact and some old wooden boxes were converted into “spares boxes” holding tubes, crystals, coils and a few other items. The set looked pretty realistic, even if it was not really wired to work. I ran across a set of plans for a vibrator power supply that worked from either 110 volts or a 6 volt battery. One day I was at Vulcan Surplus in Tampa and managed to get all the parts needed for a vibrator power supply. The transformer did not have a 110 volt winding in the primary but that was not a major problem. Again I drew up a cardboard pattern for a power supply that would fit into a .50 cal size ammo can. I got all the components mounted and wired. I was not certain if I had done it correctly and wanted someone to check it out for me before I put power to it. No one locally could do anything on it. The local outfit that works on old time car radios refused to even look at it as it was not an “Old time Car Radio” It too joined the R/T unit sitting on the shelf. As previously mentioned, a friend in the Baltimore area managed to get the Ordnance Museum director to take the original set out of the museum case and he took some very detailed photos of the set. The original model was nothing like I had imagined and my re-construction was completely different than the original. I decided to start over. I made up a new template and built a second set. This set worked and is on display. The original attempt was relegated to the corner to collect dust. In 1997, some 10 years after I had started the original project, I became acquainted with Mark Gluch in the Detroit area. I contacted him, and sent the vibrator power supply up to him. He managed to get it working and sent it back to me. He got the vibrator portion working but it quickly burned out several of the capacitors as the secondary of the power transformer was incorrectly wired. Replacing the capacitors that were damaged, the power supply came to life. Running from a 6 volt storage battery, it puts out 375 volts and 150 volts with no load on it. Now what? I started wondering if the receiver and transmitter could be made to work. I dug out the original set and tore apart the wiring in the transmitter and rewired it as the standard classic 6L6 transmitter that was described in the book, “GOLDEN CLASSICS OF YESTERYEAR” by Dave Ingram,K4TWJ. Of course the 6L6 tube was too big for the set as built so I planned to use a 6V6 tube which is about an inch shorter. I figured if the 6V6 was good enough for the WW II British Para set, it would work here. Once rewired, I sent it back up to Mark Gluch to see if it was working. The receiver was a bit more of a challenge. I found a circuit in the RCA Receiving Tube manual that looked like it would work. It called for 12 volt, 35 volt and 50 volt filament tubes running from 110 VAC. I managed to come up with 6 volt miniature tubes that would work and began to redesign and re wire the set. The tube line up that was selected was the 6 BE 6, Pentagrid Converter, 6 BA 6 as IF amplifier, 6 AV 6 as Diode detector, Audio Amp and AVC and a 6 AQ 5 as the power amplifier. While this set never saw service in the Vietnam War, it is representative of the type radios that could be built in clandestine underground factories, with a minimum of tools. Tin shears, a power drill, a hole punch, soldering iron, screwdriver, files and a volt meter were about all that I had to work with, when I assembled this radio. Another almost ran set In the process of researching circuits that were in existence and simple to build in the 1945 to 1960 time frame, I came on a two tube regenerative circuit called the “Doerle Globe Trotter”. I constructed a small set about 4 inches by 2 inches by 10 inches which would fit into the standard AK 47 style ammo bandoleer. The battery pack was the same size and antennas, headphone and other accessories fit into the side pockets. It worked reasonably well for the broadcast bands in central Florida. With a little experimentation, it could have been made even smaller. I used a Type 19 tube. Since that time, I have found a report on a Japanese WW II radio called the 1568 radio which used three 1 T 4 tubes. A similar miniature tube could have been used for a smaller set. The conclusions I made from constructing these “almost rans” is that all sorts of radios could have been made by the Viet Cong and probably were. They were limited only by their imagination and availability of parts. A second conclusion is that anyone trying to collect Chinese/NVA/VC radios needs to be aware that replicas can be easily made of the VC ammo can radios. Unless well documented, the radio is worth the price of the parts and a small amount for the labor, depending on how much labor is involved North Vietnamese Agent Radio In 1994 the Central Intelligence Agency declassified many documents to include an article in an in-house magazine titled Adversary Agent Radios that was written by James J. Fauth and published in Vol. 10 the Winter Issue 1966. Despite several errors, the article had some good information. There were three considerations for agent radios, beyond the basic one of signal strength (and consequent circuit reliability) which were paramount in the design of agent radios, Security, portability, and simplicity of operation. Simplicity of operation was the inverse of the requirements for operator skill and training. The more sophisticated the equipment, the less training was required. The article discussed Bulgarian, Polish, Soviet, East German and the Asian bloc which included China, Korea and North Vietnam. The Asian bloc radios were less impressive and less disparate than in Europe. All used older techniques as Soviet knowledge of high speed automatic keying systems was not shared with the Asians. The most advanced radio shown was a Chinese set supposedly made in 1963. A North Korean set was shown which was hand made and came complete in a large storage chest. The North Vietnamese set that was shown was listed as being of 1963 vintage but I question the accuracy of the CIA’s dates. The set was probably captured in 1963. Looking at a 4th generation photocopy does not provide much detail but the set appeared to be two sets, probably a receiver and a transmitter. The parts were mounted on a front panel or a chassis panel which was attached to the front panel. The “chassis” had no side panels for strength. Guessing at the size, based on the components the sets were probably 12 inches wide and 6 inches high. The “chassis” portion was probably about 4 inches deep. Both sets were mounted in a metal chest, much like some of the WW II Japanese sets. The one set that was removed from the case looked much like the Japanese TM Handy Wireless set which slid in and out of a case. While the Japanese set was a bakelite panel attached to a wooden base, this set was made of metal. The caption under the picture read: ”A simple two tube transmitter and regenerative receiver believed to be used by the Viet Cong. The system is contained in a crude square container; it apparently operates on dry cell batteries.” The CIA article said that operating from jungle base camps, constantly on the move and communicating over ranges of 100 to 200 miles the set was adequate. I tend to question that this was an “Agent Radio” in the true sense but more likely just another of their home brew sets used for all forms of communication. WILLIAM HOWARD ORDNANCE TECHNICAL INTELLIGENCE MUSEUM e-mail wlhoward@gte.net Telephone AC 813 585-7756 *********************************************** MEMBERS WRITE; Dennis, Joe Senger was kind enought to donate a WW II vintage Japanese oscilliscope to my museum. Another benefit of group membership. Never would have heard of each other with out the group. The unit will make a nice addition to the small display of test equipment and component parts display. Again, many thanks for sending it to me. Bill Howard ---------------------------------------------------------------------------------- Hi Bill Just wanted to drop you a line and let you know that I have enjoyed the articles on the NVA and VC comm equip. Lots of good info ---- Thanks !! Kevin Hough KG0QE Farmington, MN. KG0QE@juno.com ---------------------------------------------------------------------------------- Has anybody heard any Burrowing Owls yet? Biologist Trefry says she has not received reception reports from any researchers or amateurs. She writes: "We are not having a very early spring here (despite El Nino), so I suspect the birds have not reached Canada yet." Don't stop listening now! The migration period may continue through mid-May. In case you missed the original announcement, it is reproduced below. 73 de Joe Moell K0OV homingin@aol.com http://members.aol.com/homingin/ Hams Needed to Assist Wildlife Researchers Biologists from the Canadian Wildlife Service are seeking help from ham operators and monitoring enthusiasts. Twelve endangered Burrowing Owls were being followed on their migration south from Saskatchewan last fall. Bad weather kept tracking aircraft grounded and the signals from the owls' radio collars were lost in North Dakota. Researchers think that, if alive, the owls are now in southern Texas or nearby in Mexico. They are expected to begin their northward journey around the last week in March. The exact migration time is uncertain, and it could extend to mid-May. If you have a scanner or extended range two-meter receiver and live in central states between Texas and North Dakota, you can assist by listening for the radio tags, which emit pulsed signals near 170 MHz. They have greatest range at night when the birds are in flight. Your help is especially needed if you have portable direction finding equipment. For more information including exact frequencies, technical tips and how to contact the biologists, see the K0OV Radio Direction Finding Web site: http://members.aol.com/homingin/ *********************************************** HUMOR; A young man once asked God how long a million years was to Him. God replied, "A million years to me is just like a single second in your time. Then the young man asked God what a million dollars was to Him. God replied, "A million dollars to me is just like a single penny to you." Then the young man got his courage up and asked: "God, could I have one of your pennies?" God smiled and replied, "Certainly, just a second. --------------------------------------------------------------------------------- Stupid people I saw a lady at work today putting a credit card into her floppy drive and pulling it out very quickly. I inquired as to what she was doing and she said she was shopping on the internet, and they asked for a credit card number, so she was using the ATM "thingy". - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - I worked with an individual who plugged their power strip back into itself and for the life of them could not understand why their computer would not turn on. - - - - - - - - - - - - - - - - - - - - - - 1st Person: "Do you know anything about this fax-machine?" 2nd Person: "A little. What's wrong?" 1st Person: "Well, I sent a fax, and the recipient called back to say all she received was a cover-sheet and a blank page. I tried it again, and the same thing happened." 2nd Person: "How did you load the sheet?" 1st Person: "It's a pretty sensitive memo, and I didn't want anyone else to read it by accident, so I folded it so only the recipient would open it and read it." - - - - - - - - - - - - - - - - - - - - - - I recently saw a distraught young lady weeping beside her car. "Do you need some help?" I asked. She replied, "I knew I should have replaced the battery in this remote door unlocker. Now I can't get into my car. "Do you think they (pointing to a distant convenience store) would have a battery for this?" "Hmmm, I dunno. Do you have an alarm, too?" I asked. "No, just this remote 'thingy,'" she answered, handing it and the car keys to me. As I took the key and manually unlocked the door, I replied, "Why don't you drive over there and check about the batteries...it's a long walk." - - - - - - - - - - - - - - - - - - - - - - Tech Support: "What does the screen say now.." Person: "It says, 'Hit ENTER when ready'." Tech Support: "Well?" Person: "How do I know when it's ready?" - - - - - - - - - - - - - - - - - - - - - - Several years ago we had an intern who was none too swift. One day he was typing and turned to a secretary and said, "I'm almost out of typing paper. What do I do?" "Just use copier machine paper," she told him. With that, the intern took his last remaining blank piece of paper, put it on the photocopier and proceeded to make five blank copies. - - - - - - - - - - - - - - - - - - - - - - One of our servers crashed. I was watching our new system administrator trying to restore it. He inserted a CD and needed to type a path name to a directory named "i386." He started to type it and paused, asking me "Where's the key for that line thing?" I asked what he was talking about, and he said, "You know, that one that looks like an upside-down exclamation mark." I replied, "You mean the letter "i"?" and he said, "Yeah, that's it!" - - - - - - - - - - - - - - - - - - - - - - I was in a car dealership a while ago when a large motor home was towed into the garage. The front of the vehicle was in dire need of repair and the whole thing generally looked like an extra in "Twister." I asked the manager what had happened. He told me that the driver had set the cruise control, then went in back to make a sandwich. - - - - - - - - - - - - - - - - - - - - - - I rented a movie from Blockbuster. Before the movie begins a message comes on the screen saying, "This movie has been altered to fit your television screen." Comment from person: "How do they know what size screen I have?" ---------------------------------------------------------------------------------- I'm still suffering from shock from the last war. I was almost drafted! Luckily I was wounded while taking the physical. When I reached the psychiatrist, I said, "Give me a gun, I'll wipe out the whole German Army in five minutes." He said, "You're crazy!" I said, "Write it down!" -- Jackie Mason ---------------------------------------------------------------------------------- I gave my cat a bath the other day ... they love it. He sat there, he enjoyed it, it was fun for me. The fur would stick to my tongue, but other than that ... -- Steve Martin *********************************************** (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, military-radio-guy@juno.com) ***********************************************