MILITARY COLLECTOR GROUP POST, JUNE 4/98 Index: UNIVERSAL INVERTER POWER SUPPLY, PART II; by Dennis Starks MEMBERS WRITE; Special Forces Radio in Vietnam, ON THE COMMERCIAL FRONT; Haney Electronic Co. Museum Down Sizing List, KWM-2A, PRC-127 for PRC-68s, HUMOR; *********************************************** UNIVERSAL INVERTER POWER SUPPLY, PART II; by Dennis Starks INVERTER START UP: Once you've completed winding your transformer, and have a wired circuit for the inverter, you'll next want to fire it up. Start with a power supply of about 6 volts. If it starts right up, and you have high voltage, you might just be in business. If for some reason the inverter did not start oscillation, first try reversing the feed back wires on the base of each transistor with each other. If this doesn't fix it, reduce the value of R-2 slightly until it does. If your inverter seems to be operating properly, but will not handle the required load current, reduce the value of R-2 by 100ohms at a time until it does. CONNECTING TO YOUR RADIO: Once you've completed the inverter, and the two regulators that are also associated with this supply. All has been tested and appears to work, it's time to hook it up to the radio. You'll first want to connect the heater supply, insure that the voltage adjust control on the regulator is set at it's minimum output setting(test it first without being connected to the radio!). Connect a voltmeter to the heater supply, turn the radio on, apply power to the regulator's input, then adjust it's control until the needed heater voltage is achieved. Usually, the heater voltage regulator can be pre-adjusted without being connected to the radio. In the case of 1.5 volt tubes, this adjustment will be minimal. Once the heater circuits are established, turn the control for the input voltage regulator to the inverter to it's minimum setting. Connect the outputs of the inverter to the load(radio). Connect a voltmeter to the receive B+ supply(if a multi B+ system). Apply power to the inverters input voltage regulator, slowly adjust it's control until the needed inverter output voltage is reached. You should by now hear noise in the radio's speaker. If your project is a multi B+ transceiver. Connect the voltmeter to the trans B+, insure that the near double B+ voltage is there. Now key the radio and watch this B+ voltage, also check the rec B+ again. There will be some transient voltage changes but there is nothing we can do about it. Slight adjustments of the inverter input voltage regulator may be needed to effect the optimum voltages for both transmit and receive. If inverter oscillation should drop out during transmit, refer back to "INVERTER START UP". BATTERY C0NSIDERATIONS: Only two battery types are generally available in a sufficient amp-hour rating to suite our needs. These are nicads and gel-cells. Dependant on the application either might work equally well. But there are some exceptions and facts that must first be considered. First is the input voltage versus output voltage of our inverter. A change of only one volt on the input of our inverter can produce as much as 15 volts difference on the output, enough to make the radio inoperable. To a degree, the voltage regulator we use will take care of this variance, but only if a higher voltage is available than what's needed. So proper battery type and voltage must still be carefully chosen. Second is the amp-hour rating, the average current drain of our completed power supply, including heaters, is around one amp. So to have a battery pack that will allow a usable amount of operational time, the minimum battery we can use would be a 5ahr type. Where the amp-hour rating is 5 divided by a current drain of 1 amp, equals 5, minus about 15% for internal losses in the battery, we come up with about 4.2 hours of operational time. That's practical, BUT! We must then take into account the drastically different discharge curves inherent in the two type batteries we have available. First is the nicad, it's output voltage will remain the same almost until it is discharged, thus it has a very sharp discharge curve, almost a cut off. We have the added advantage of being able to draw as much as ten time the amp-hour rating, I/E if it's a 1 amp-hour battery, we can draw a much as 10 amps and still maintain battery voltage(but not recommended). Second is the gel cell, it's voltage steadily drops as the battery depletes. Thus it has a radically different discharge curve(near linear), combined with a sometimes drastic difference between the loaded, and no-load, battery voltage. In the case of the latter, you may have a battery voltage of six volts, but when a load is connected this may drop by as much as 2 volts. Resulting in an actual supply of 4vdc, which might be borderline in some applications. So the nicads have the advantages list above, but are limited in the amp-hour rating we might be able to obtain. They are further plagued by the memory syndrome, and short shelf life(about one month/charge). But are smaller than gel cells in terms of size to amp-hour rating. Gel cells on the other hand are available cheep, in high amp-hour ratings, do not suffer from the memory syndrome, and have a much longer shelf life,I/E they will hold a charge for several months. Gel cells have other problems and advantages too, as do nicads, but space does not allow further elaboration here. What difference does all this make in our applications? A case in point, we have a very small radio, with very little internal space to house both our inverter power supply, and it's batteries, inter the CPRC-26. The inverter configuration for this radio is very much like the PRC-6, but the internal space available is very limited. We only have room enough for four "D" cell type batteries. If we use four gel cell types, we will not have sufficient amp-hour rating to operate the radio for any usable amount of time(2aphr). But we will have 8 volts available. But we only need 4 volts in this application, so two gel cells at 4 volts, and 3-4ahr should work. Not! Because of the linear discharge curve of gel-cell batteries, they will only produce 4 volts at the beginning of it's use, their voltage will then drop as the battery depletes. Thus with the borderline voltage/amp-hour rating we are able to fit in the radio we will be limited to about 20 minutes of operational time. On the other hand, 4ea "D" cell nicads will fit in the box, with a 5ahr capacity, giving us about 4 hours of operational time by virtue of it's near constant 4.8 volt output(much better). The same will hold true when trying to develop power supplies for such radios as the BC-611, MAB, DAV etc. On the other hand, where space available is not a major concern, we have more battery flexibility. In the case of a PRC-6 or PRC-10, there is a lot more room than the CPRC-26. We can then use gel-cells to maximum effect, but we must use a much higher battery voltage to compensate for the linear discharge curve. While it's still true that only 4 volts is needed to make the PRC-6/inverter work, we must use at least 6 volts or more to allow for the linear discharge curve(tapering battery voltage). Here again, the voltage regulator we installed comes into play. When designing power supplies for such radios as the PRC-10, BC-1000, etc. Our flexibility is even further enhanced by the greater space available for both batteries and power supply. In these applications, only about 8 volts is needed on the same inverter supply. But we still use an input regulator to compensate for any supply voltage that might be used. BIAS BATTERIES: Most of the radios we will be constructing power supplies for will need some sort of negative bias voltage. While it is often possible to modify the circuit we have presented here to produce this voltage, doing so will often complicate the power supply to the point that the radios original on/off switching can no, longer be used. For this reason, and in the interest of simplicity we will just use batteries for this voltage. For the most part, any small type battery can be used that will fit into the available space. Such as "N" cells, "AA", or "AAA" types. It doesn't really matter as the current drain of these bias circuits is so low that the battery will usually last it's normal shelf life anyway. Do not use "C", or "D" cells as you'll just be wasting money, and room, and adding weight. Use quality batteries, not "longer lasting", just quality made. Because these batteries will be in your radio for a long time, and you don't want them leeking all over the place. As always, if you have any questions, comments, or input, please let me know. Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN military-radio-guy@juno.com Related Topics: MCGP, MAR.12/98, MAKING CONNECTIONS; Power Connectors In a Pinch, by Dennis Starks MCGP, MAR.13/98, MAKING CONNECTIONS; More Ideas MCGP Backmail #28; PC board makeing for dummies. By Dennis Starks MCGP Backmail #32; Alternate Power Sourses. All persons interested in this topic are strongly advised to read this file. It details much of the information given in this series, and debate from several of our members on the subject, thus giving an understanding of how our specs etc have been arrived at. *********************************************** MEMBERS WRITE; Special Forces Radio in Vietnam, I received ths information from a SF Veteran of Vietnam and also a member of Texas NG LRRP unit. Thought you might be interested in the information. Bill Howard ---------------- WHAT DO YOU REMEMBER OF THE USE OF THE AN/GRA 71 CODE BURST TRANSMITTERS AND WHAT RADIOS DID YOU USE. DID YOU ALSO MAKE USE OF THEM IN VIETNAM. Yes. Its was used with the AN/PRC-74. We had them in G-143 until replaced by the AN/PRC-70 and the digital message device group (DMDG); all much better equipment. Some LRRP units in Nam used the 74, but SF seldom did, except for some of the reconnaissance projects. I never heard of them using the AN/GRA-71 with it, just voice or manual Morse. ed) I think he meant that the PRC-74 was "eventually" replaced by the 70, but not necessarily in Vietnam, which is partially true. But I serious doubt that any PRC-70 saw service in Vietnam except possibly in an experimental capacity. This because the experimental models were not tested from AVCO, & General Dynamics until June 1971, this resulted in the first order of 21 (test) units from AVCO in late 1971, or early 1972. This initial run of test models was to be filled over a 33 month period of time. That would mean that the first "TEST" run of radios would not have been completed until after the Vietnam war. By 1966, the PRC-74 had begun to filter it's way in to Special Forces base camps, though at the time, it was still pretty much a new toy, and not yet their mainstay radio. As reported in the May 1966 issue of "Electronics" magazine Sgt Harold Palmer, Special Forces signalman at Duc Co explains the radio equipment they have on hand: The GRC-109 and it's two antennas, both 100ft long, one strung to a poll, the other buried 12" deep inside a 1" plastic tube. The PRC-64 "Our newest radio, we've only had it a couple weeks", results with it had thus far been favorable. The HT-1, and TR-20,"On patrol we take the HT-1", "We use the TR-20 in the communications room for communicating with it", "The HT-1 isn't water proof, however, and actually isn't rugged enough." Other radios the Sgt comments on are the PRC-25, and KWM-2A. Major Anthony Scibilia, Group Signal Officer for Special Forces headquarters in Nha Trang, comments: On the PRC-74, "other A detachments have additional radio equipment. Some use the PRC-74", " formerly called the HC-162D", "Although it's transistorized, it's still too heavy". He go's on to describe the PRC-25, FRC-93(KWM-2A), URC-11, & GRC-26. It would have been nice if your friend could have elaborated a little more on both these radios, and any others(experimental or otherwise) then, and now. *********************************************** ON THE COMMERCIAL FRONT; Haney Electronic Co. J-45, leg iron CW keys, Correct for BC-1306, GRC-9, GRC-109, and PRC-47. These are new old stock units most still in original packaging, several contract dates from 1968 to 1980's. They include cord CD-201A with PJ-055B connector. The member price is $20.00ea. AS-2975, PRC-70 dipole antenna kit. Unused Similar to that use with the PRC-74 differing mainly in the balun it uses. The member price is $25.00ea. H-250 handsets, new, latest issue. $17.50 ea U-229 audio connectors, $1.00ea U-77 audio connectors, $2.00ea PRC-25 or 77 battery connectors, removed from battery, with white plastic spacer. $1.00ea PRC-70 Selector assembly, unused, forest green. NSN 5820-01-092-5904, also called the A1 module. This is part of the front panel, with 6 frequency select knobs, and readouts, controls for power, mode, volume, and squelch. Includes printed circuit board with microprocessor. $60.00 STEVE HANEY ed) Steve has a list of manuals available on request via email. ---------------------------------------------------------------------------------- Museum Down Sizing List, The Louisiana Museum of Military History, due to financial realities will be will be moving to smaller quarters. We have been asked to help liquidate some of the Commo gear. Below is the first list of equipment that's been made available. If you have an interest in any item contact Joe below via email and he'll pass along any needed info. AM-1780, untested but good condition, $ 25 AM-2060, with cable, $ 95 AS-2851, 30-80 log periodic complete, $ 125 BB-451, NOS with electrolyte kit, $ 185 BB-451, used, $ 100 BC-639, untested but good condition, $ 35 CU-2267/GR, Five unit multicoupler - with two spare F-1482, $125 CY-6121/PRC-74, Wet cell battery box, $ 25 DY-105, untested but looks good, $ 45 DY-105, no dynamotor, $ 25 GRA-71, almost complete, $ 125 GRC / VRC, lots of cables, ASK GRC-109, details later GRR-5, ASK MD-522, with cables, $ 100 PPS-4, complete except for optical sight, $ 300 PRC-25, with accessories, $ 300 PRC-41, with antenna / PP-3700 AC supply - working, $ 175 PRC-68, with handset, antenna and battery - working but a little rough, $200 PRC-68, with handset, antenna and battery - working, good condition, $ 235 PRC-77, with accessories, $ 350 PRC-90, with battery - working, $ 100 PRC-90, with battery - no 282.8 transmit, $ 50 PRR-9/PRT-4A, working w/manual copy, $ 50 R-392, good condition with power cable, $ 200 R-442, working, good condition, $ 225 RT-524A, unchecked, $ 300 RT-524A, working, $ 500 RT-68, no meter, $ 40 RT-858/PPS-6, RT only, Make offer Russian 62R1, VHF cargo pocket transceiver with mike and dipole wire antenna - ASK Make offer Russian R-105M, no accessories, $ 100 Russian R-108, no accessories, $ 100 TRC-77, untested but good condition, $ 75 TS-323, good condition, $ 35 TT-722/TG, untested, $ 50 ITEMS NOT FOR EXPORT All reasonable offers will be considered All items plus shipping Payment to: Glen Thibodeaux c/o Louisiana Museum of Military History P. O. Box 92110 Lafayette, LA 70509 Glen is looking for PRC-64 accessories, G-43 or G-58 generator and M-1 Carbines / accessories. If folks would just contact me directly, I will take care of getting things to Glen. Joseph W Pinner EMail: kc5ijd@sprintmail.com ---------------------------------------------------------------------------------- KWM-2A, I am posting this for a friend without net access. KWM-2A Transceiver (RE) 516F-2 AC Supply in Speaker Cabinet (RE) 312B-5 External VFO/Console (RE) 30L-1 Linear Amplifier (WE) CP-1 Crystal Pack All excellent condition with manuals $2,150 Contact: Phil Goodman - W5YVT (770) 509-9493 ---------------------------------------------------------------------------------- PRC-127 for PRC-68s, Sending this for a friend. Will trade PRC127 with handmike, drop in charger & 12 volt adapter for 2 PRC 68's. Send response to following E-Mail: kb0yit@platec.net Thanks, Norman E.Davis *********************************************** HUMOR; Fred goes to a doctor and says, "Doc, I want to be castrated." Doc says, "Look, I don't know what kind of cult you're into or what your motives are, but I'm not going to do that sort of operation." Fred: "Doc, I just want to be castrated, and I'm a little embarrassed about talking about it, but I have $5,000 cash right here. Will you do it?" Doc says, "Well, OK, I guess I could make this one exception. I don't understand it, but OK." He puts Fred to sleep, does the trick, and is waiting at the bedside when Fred wakes up. "Well, Doc, how'd it go?" Fred asks. "It went fine, just fine. It's really not too difficult of an operation. As a matter of fact, $5,000 is a lot to pay for such a simple task, and I felt a little guilty about taking that much. So, while I was operating, I also noticed that you had never been circumcised, so I went ahead and did that, too. I think, it's really better for a man to be circumcised, and I hope you don't mind my..." "CIRCUMCISED!" yells Fred. "THAT'S the word!!!" ---------------------------------------------------------------------------------- MORE BUMPER STICKERS: Who lit the fuse on your tampon? Support Cannibalism-EAT ME! God is my co-pilot, but the Devil is my bombardier. I don't have a license to kill. I have a learner's permit. I wasn't born a bitch. Men like you made me this way. Keep honking while I reload. Taxation WITH representation isn't so hot, either! Who were the beta testers for Preparations A through G? Madness takes its toll. Please have exact change. 5 days a week my body is a temple. The other two, it's an amusement park. EARTH FIRST! We'll strip-mine the other planets later. Your child may be an honor student but you're still an idiot. If you drink, don't park. Accidents cause people. If you can read this, I can hit my brakes and sue you. Save the whales! Trade them for valuable prizes. Whitewater is over when the First Lady sings. Jack Kevorkian for White House physician. Just say no! to sex with pro-lifers. My wife keeps complaining I never listen to her ...or something like that. Sure you can trust the government! Just ask an Indian! Alcohol and calculus don't mix. Never drink and derive. If we are what we eat; I'm cheap, fast, and easy. Stop repeat offenders. Don't re-elect them! ---------------------------------------------------------------------------------- Jerry Falwell was seated next to President Clinton on a recent flight. After the plane was airborne, the flight attendant came around for drink orders.The President asked for a whiskey & soda, which was brought and placed before him. The attendant then asked the minister if he would also like a drink.The minister replied in disgust, "Ma'am, I'd rather be savagely raped by a brazen whore than let liquor touch these lips!" The President then handed his drink back to the attendant and said, "I'm sorry, I didn't know there was a choice.I'll have the same thing he's having". ---------------------------------------------------------------------------------- Once upon a time, a beautiful, independent, self assured princess happened upon a frog in a pond. The frog said to the princess, "I was once a handsome prince until an evil witch put a spell on me. One kiss from you and I will turn back into a prince and then we can marry, move into the castle with my mom and you can prepare my meals, clean my clothes, bear my children and forever feel happy doing so." That night, while the princess dined on frog legs, she kept laughing and saying, "I don't think so." ---------------------------------------------------------------------------------- This morning there was ice on the pipes in my apartment. But the landlord fixed it. He put antifreeze in the radiator. -- Herb Shriner *********************************************** (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 or this group are included. For more information conserning this group contact Dennis Starks at, military-radio-guy@juno.com) ***********************************************