Military Collector Group Post

Backmail #59

(12 pages) Index: COUNTERMEASURES/SURVEILLANCE RECEIVERS; From Spencer Bahner & Dennis Starks MEMBERS WRITE; More R-1444 TRP-4, MYSTERY JAPANESE GREEN RADIO; From Breck Smith AN/URC-100 SERIES; Part I, by Richard Lacroix PRC-74 SELECTABLE SIDEBAND; Jim Karlows Contribution RBS RUMINATIONS; By Hue Miller NAVY RBM SERIES; *********************************************** COUNTERMEASURES/SURVEILLANCE RECEIVERS; Dennis, I am looking for a couple relatively recent solid state mil receivers: AN/URR-69 or R-1444/UR HF receiver and R-1518/UR Vhf receiver I also have a dumb question for the mail list group. Here goes: How exactly were 'countermeasure' receivers used? Many of these Rxs were manually tuned and would have been difficult to use to find 'hostle emitters' under combat conditions- was that how they were actually used or am I missing something. I guess that role would have been OK for units in a stand-off position (like naval vessels or land based support facilities) but I am unclear on details of military useage of this kind of surveillance receiving gear. Feedback? Thanks, Spencer Bahner --------------------------------------------------------------------------------- Spencer, There has always been several different varieties of "Countermeasures", or "Surveyance" receivers each having a different intended purpose in life. And with these different purposes, there was a correspondingly different type receiver used. Some of the purposes are as follows. #1. "Intercept" receivers, to detect, monitor, and derive intelligence from enemy traffic. In this capacity we have a fair quality communications receivers usually used in a fixed location. Located far remote, and usually on a different continent than the subject signals being analysed. Beginning in WW-II a series of Hammerlund designed radios were used almost exclusively in this role. They included the BC-779, BC-794, R-270, BC-1004, etc. All these receivers were physically identical, differing mainly in frequency coverage. Used in conjunction with each other in systems like the SCR-244, and FRR-12, it is to their credit that the cracking and daily decoding of both German and Japanese codes can be attributed. Later came such receivers as the R-274(SP-600), and R-274D(SX-73), which could cover the entire spectrum between 500kc and 54mc in a single package. With this increased frequency agility also came the ability to use a single type receiver to performed the tasks of other intercept/monitoring/communications duties that previously required a host of different types of equipment employed in as many different capacities. #2. To analyze and derive intelligence from the enemy signal itself. On the HF bands, quality receivers that might have included a Panoramic indicator like the BC-1303, or the exotic Navy RBY which was an SX-28 with an integrated panoramic adapter. Not restricted to intelligence operations, receivers of these types would also perform the functions of spectrum management, or general communications, and monitoring. On the VHF/UHF bands, the APR-4, and APR-5, or the Navy's RDO, or RDZ might be used. They were used to detect, analyze, and locate enemy radar as well as other signals. In the case of these, the band pass was purposely wide to both pass the wide radar pulse signals they were to detect, and to allow fast manual tuning or "scanning". Much of the very exotic and specialized Watkins Johnson equipment found today had a similar purpose in life as the receivers noted in this category. #3. Dual purpose Surveyance, of either enemy, or allied traffic. Closer to the front lines, receivers like the BC-787, Hallicrafters S-27, or S-36(the famous "UHF" receivers) were used to keep track of enemy movements. Capable of operation between approx 27-120mc, either AM or FM. These receivers were used to monitor tactical enemy traffic, usually of armored columns, providing information on troop movements, and concentrations. But every bit as important was their use to monitor friendly traffic. Patton himself kept an S-36 close at hand as it was his best source for up-to-date information on the problems or fast pace progress of his own command. Intelligence operators also used this equipment to insure that proper radio doctrine/security measures were being observed by troops in the field. #4. Direction finding. Also in close proximity to the front lines were the direction finders. They might include systems like the WW-II SCR-255(BC-903), SCR-503(BC-1003), or the postwar R-395/PRD-1, and a host of others. Each considered to be field portable(a very loosely used term to say the least), they were used for the spot location of either friendly or enemy transmitters. All these receivers were provided with a rather broad IF bandwidth, and fast tuning, both to facilitate faster manual "scanning" of the frequency spectrum minimizing the chance of inadvertently passing over a suspect signal. You might note, that while the R-395 was grossly obsolete shortly after it's introduction, it received widespread use in Vietnam, and was still listed as a current issue item until about 1983. A step down from the above would be the real close in direction finders, like the SCR-504(famous suite case receiver), or the Navy DAG. Both used to narrow down the location of an enemy or clandestine transmitter to within a few yards. Beginning in the late 50's, and progressing into the late 70's, there was an ernest attempt to develop, and adopt a receiver, or set of receivers to replace the monster R-395. Until such receivers as the R-744/PRR(VHF), and R-901/GR(HF) appeared in the late 50's, systems actually billed as "test equipment" would see "stop gap" use in direction finding. These referred to as "interference measuring and detection sets" they were mainly built by Stoddard and other companies usually associated with test equipment. Included were the R-178/URM-3, NM-50, NM-52, and a host of others. While some were very complex in the array of antennas and accessories they included, all were blessed with the same wide bandwidth and fast tuning of their predecessors. While the use of these varied "Test equipment" types continued possibly as late as the early 80's, the 60's saw a steady succession of experimental receivers interring the field. Like the R-1410XE(solid state VHF), though still having experimental nomenclature, it is possible that it was built in sufficient quantities to actually have seen service in the field. Or the R-1218(XE-3) of 1968 which would actually be adopted and included with the R-1518(it's VHF twin) in the TRQ-30 set. Possibly the first truly portable, solid state direction finding system to receive official adoption. At the same time came the R-1484/PRR-15 possibly only adopted by the Marine Corps out of desperation or impatience with the dilly dallying of the other services. Desert Storm saw the use of commercial "Scanners" built by AOR, and capable of HF/VHF/ and UHF multi mode operation. Possibly only acquired as an expedient, they were bought up by the military in such quantities that the civilian market suffered greatly. The R-1444 on the other hand, does not really fit the niche of a direction finder. While it is certainly capable of direction finding, I'd sooner category it as an auxiliary receiver intended to be used in the same role as or possibly even as a replace for the GRR-5. I hope that I've answered some questions, and posed some others without thoroughly confusing everyone. Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN *********************************************** MEMBERS WRITE; More R-1444 More R-1444, Hi Dennis, I must respectfully question your remark that compares the R-1444 to an "auxiliary receiver", ala the GRR-5. As a proud owner of one, let me point out the specs: 0.5-30 MC in 100 Hz steps, all-mode (AM, USB, LSB, CW, and *FM*), 3 IF bandwidths (1, 4, and 25 KC), sensitive, small, portable, 3 power options. Has a 'recorder' output (fixed audio level). Has 50 ohm or whip antenna connections. Has a 'scan' selection, which mechanically multiplies the tuning rate by a factor of 10. RF gain with AGC setting, and a tiny signal strength meter. The front dial glass is shielded (to keep radiation in, I assume). Call me crazy, but that sounds like a fairly high-end portable intercept receiver to me. Pete ed) the more you describe your R-1444(another radio I don't have, and want), the more it does sounds like a universal axillary receiver. Possibly even intended to replace the GRR-5(as that is what this receiver was meant for and no other known receiver ever replaced it). As noted in the article, there is a big difference between an "Intercept" receiver, and one intended for DF work. Also note what I wrote "While it is certainly capable of direction finding", " I'd sooner category it as an auxiliary receiver intended to be used in the same role as, or possibly even as a replace for the GRR-5". Also note the word "Possibly"! Just for the sake of argument, let us compare the R-1444, and the GRR-5. R-1444, sensitive, small, portable, 3 power options. GRR-5, small(for it's day), portable(for it's day), sensitive, "5" power supply options. R-1444, Has 50 ohm or whip antenna connections. GRR-5, Hmm, it does too. R-1444, 'scan' selection, which mechanically multiplies the tuning rate by a factor of 10. GRR-5, Me too! R-1444, RF gain with AGC setting, and a tiny signal strength meter. GRR-5, RF gain, and AVC I got. But no tiny meter, shucks! R-1444, Has a 'recorder' output (fixed audio level). GRR-5, I ain't got this either, but neither did any other receiver until 1968. Jane's 1981 describes the R-1444/URR-69,"It is used either as a general-purpose receiver or as an axillary equipment in a direction finding system". The text go's on to say that the set is in widespread use with US Forces all over the world. Typically, DF sets are not built in very large quantities. The current field DF set(or was until a couple years ago), is the TRQ-30(I have two of them). The one in my collection was retired from service with the 501st Military Intelligence, and consist of R-1518/UR (20-150mc AM/FM/CW in two bands), R-1218/UR (.5-20mc AM/USB/LSB). DF Loop Antennas AS-1523(.5-21mc), AS-1526(19-50mc), AS-1527(45-100mc), AS-1528(95-157.5mc), AB-1110 Ant. Pedestal/Tripod, and PNH-7 recorder. It is entirely possible that the R-1444 is, or can be, a direct replacement for the R-1218. But I still contend that it's primary role is that of a general-purpose receiver, and it's direction finding qualities are only secondary. Dennis *********************************************** TRP-4, MYSTERY JAPANESE GREEN RADIO; From Breck Smith Information follows on Japanese radio that I am trying to obtain information on. TRP-4 made by OKI Electric Co. Ltd, Tokyo Japan. The 10.5 inch x 5 in x 10 in chassis has the words TYPE TRP-4 SSB- TRANSCEIVER in the upper left of the front control panel above the first row of controls. Length measurements are without the battery box which extends the length another 3 inches. On the bottom is a placard with the same info but has a design #31085 and what appears to be a date of 1963.1 and SN of S-3587. The unit is sort of a strange green, the contols look like PRC-10 items, there are corner posts that extend out from the corners to protect the unit just like the PRC-10 , the unit has two standard audio connectors on the left side, one above the other and accepts standard handsets(H-33 etc). There are two rows of controls that are next to each audio connector and go across the front panel. The first row has a PUSH ON button for keying, a large volumn control, a stardard square meter(marked with the OKI symbol ) an ANT TUNE, Knob and a large recepticle for a ROD ANT(again like a PRC-9). The second row of controls next to the audio connector are a SYSTEM SWITCH marked off,rec, Send-A1, RT and ANT TUNE, then there is a CLARIFIER knob and a channel select know which selects 6 crystal controlled channels. Below the rod antenna is a Aux antenna connector with a small nut to hold the wire and a ground connector marked "E" The unit is functional and runs off of 7.5 VDC with the chassis being at a positive potential(being familiar with 1960's vintage japanese radios I checked this before the smoke test!) The unit is solid state and has a high voltage switching power supply in the battery box which is attached to the bottom of the radio with 6 hasp fasteners over center fasteners. The power supply appears to run best at 7.5 volts and as the voltage input is increased the interior section starts to regulate at 7.5, maybe the unit is designed for 12 volts but I was afraid to try any higher once I got the thing working. As you drop below 7.5 all the low voltages drop so the regulator is set for 7.5. High voltages measured were in the 200 volt range. On transmitt one bias voltage is generated in the the -26 volt range. Inside the battery box/ power supply, it has the label of DC-DC converter and also has terminals for the "hand crank generator". There is a large two wire military connector on the side and I tried a cannon connector shell on the threads and it fit. The battery box connects to the R/T unit with a bundle of blue wires, all the same color. The battery box is sectional with one section for a battery and other section contains the switching power supply(solid state) and a relay. Alone the center of the box is a divider which contain the plug, and four conecters with nuts , the center of which is red and black. The unit was tested and operates from 2.8 up through 8 mcs and is on LOWER SIDEBAND. The IF is 455 kcs. The channels appear to be frequency sensitive, you can only operate 2.8 mcs on the lower channels and say 7.1 mcs on the upper channels. The final amplifier is a tube type 5A6 on which I have no information.. Current draw is 20 to 50 mills with signal being received and on transmitt is approximate 2 amps. Inside the R/T unit are two sections, receive and transmitt. The receive section has a large 1 inch by 2.5 in filter labeled CM filter and has a DATE of 9-62 which confirms the previously mentioned date. The interior has not been sprayed or painted with any sort of anti -moisture or fungus material. The connector on the rear of the RT unit mates with the power supply cable and the connecor has three rows of pins , looks very similiar to R-174 receiver(ANGRR-5) but is larger has more pins. The receiver is contructed of three main boards one on top and the other is on the bottom, a small audio board is mounted on the side. The boards are soldered/hardwired. The RF section has two small air variables , and six trimmers for the channels. The entire RF section is hard wired, no boards, there are 6 cystals and standard HC-25 ceramic sockets and have a retaining clamps with a thumb screw. On the top of the retaining clamp for the crystals is a label" 2NDOSC(X-TAL). There is a single RT relay mounted below the airvariables and it is enclosed in clear plastic but is soldered in place, no socket. The ANT TUNE control on the front appear to operate a large slug that goes in and out of a three inch tube with wrapped turns to tune the antenna. Next the the final tube which has a shield are two more trimmers marked 5 and 6. Any info would be appreciated Breck K4CHE, Dover Delaware Ed) The 5A6 is the same output tube as used in PRC's 8, 9, & 10. This would place the RF output of the set around 4-5 watts PEP. A most interesting set, it's a shame you weren't able to get some clue from the person you purchased it from as to how it got to this country. If it has any crystals still in it you might check their frequency to get an idea of what type service it had been used in. *********************************************** AN/URC-100 SERIES; Part I, by Richard Lacroix The Motorola AN/URC-100 series of radios evolved from the PT-25A Portable Emergency Transceiver (1978). Prior to nomenclature assignment, the= original AN/URC-100 (NSN 5820-01-112-0176) was known as the PRT-250 (Motorola model number). The design concept of the URC series is to develop a multi-purpose radio system that would accommodate manpack, aircraft, shipboard and vehicular uses in the VHF and UHF air bands. The design is fully solid state and fully synthesized. As a manpack set, the radio is nomenclatured the AN/URC-100. In an LOS/SATCOM configurations, it is known as the AN/URC-101 (NSN 5820-01-112-0177). For SATCOM applications, the URC-101 had both transmitter output power and receiver sensitivity increased. Modes of operation for the URC-100 & URC-101 include AM or FM clear or secure voice and a 300 Hz to 2.5 kHz linear swept baseband beacon signal. Both= sets have a frequency range of 116 to 150 MHz and 225 to 400 MHz in 25 kHz steps. The first variation of the URC-100 appears as the AN/URC-100(V) which replaced the original 116 to 150 MHz VHF band with the tactical 30 to 88 MHz band and saw the addition of the standard 150 Hz squelch tone for compatibility with VRC-12 series and PRC-25, PRC-77 series radio sets. The variations in the URC-101 include a AN/URC-101(V) which is deemed a data transceiver. The changes include 5 kHz channel spacing in the 116 to 150 and 225 to 400 MHz bands. Also, this unit saw the addition of extra RF connectors to the front panel labeled IF, UHF OUT and UHF IN located on the far left of the transceiver between the HANDSET and the UHF ANTENNA connectors. The connectors provide 70 MHz IF baseband compatibility for use with the= Motorola PM-15 Adaptive Tactical Modem. A second variation to the URC-101 includes a VHF band change from the 116 to 150 MHz band to the 100 to174 MHz band in the FM mode only with a 2.5 and 25 kHz spacing and is nomenclatured the AN/URC-101(V)2. The UHF band remains unchanged and the output RF power is 1.5 or 5 Watts. With the progression of time and the requirements for a tactical VHF/UHF transceiver, with nomenclature that would stop all confusions of "which band does this radio operate on?", Motorola released the AN/URC-104 (NSN 5820-01-131-5674) and the AN/URC-111 (NSN 5820-01-152-3185) respectively. Both sets feature operability in the 30 to 88 MHz band with 150 Hz squelch tone and 225 to 400 MHz band. Channel spacing is 25 kHz. The design principals are for a radio set that is suitable for ground-to-air/air-to-ground and tactical point-to-point operations. The units also operate in clear or secure voice or data modes and are compatible with the KY-57, KY-58 cypher equipment. All previous URC features are included in these current version radios. Also introduced at the same time is a specific data transceiver known as the AN/URC-110 (NSN 5820-01-151-4199). The URC-110 operates in the 116 to 150 MHz band and in the 225 to 400 MHz band in 5 kHz steps. The URC-110 is designed with a low noise synthesizer to permit operation with tactical modems such as the Motorola PM-15A and meets satellite architecture requirements. The URC-110 can also function as a repeater/frequency translator. For LOS/SATCOM use, the AN/URC-112 (NSN 5820-01-151-4198) was introduced and is labeled as an "LOS/SATCOM transceiver". Frequency coverage includes 160 to 172 MHz with 2.5 kHz channel spacing and 225 to 416 MHz with 25 kHz channel spacing. The URC-112 can be made compatible with the AN/UYA-7 & AN/GYC-8 transceivers and the AN/UGC-129 and AN/UGC-74 message devices. The URC-112 will operate in the appropriate mode with the AN/ARC-164, AN/ARC-171 and the AN/WSC-3 transceivers. Some accessories for the above radio sets includes various AC, DC, AC/DC power supplies and battery boxes, antennae, modems etc... The most varied accessory appears to be the battery box. For the most part the "box" or enclosure appears to be common but the inserts vary from a PRC-25 battery insert, a Lithium battery insert PL-1500/URC (PTL-110A) which uses 2 BA-5590/U Lithium batteries, a NiCad battery insert (PP-7962/URC (PTMG-120)) with build-in multi-voltage charger which uses 2 BB-590/U batteries and a rechargeable NiCad "D" cell box complete with built-in 120/240 VAC charger. Further= power sources include a 28 VDC adapter box which employs standard VRC series DC connectors and a universal power supply, the PP-7961/URC (Motorola number PTAD-101A) which includes input voltages from 120/240 VAC and 24 VDC. The modem, PM-15, is an Adaptive Tactical Modem operating at 300, 1200 and 2400 bits/s. This unit requires a 70 MHz RF interface and 1 BA-5590/U or BB-590/U battery to operate. Modulation formats are differentially encoded bi-phase shift keying (dbpsk) for the 200 and 1200 bits/s modes and, differentially encoded quadraphase shift keying (dqpsk) in the 2400 bits/s mode. Also available is a UHF, 200 Watts RF linear power amplifier nomenclatured the AM-7175/URC (NSN 5895-01-175-9853). The AM-7175/URC is a variable, 50 to 200 Watts, (by a rotary knob on the front panel) output RF power amplifier that operates in the AM, FM and CW mode and will deliver 50 Watts in AM (200 Watts peek) and 200 Watts in FM mode, requires a 2 to 25 Watt input RF power drive. Richard Lacroix *********************************************** PRC-74 SELECTABLE SIDEBAND; Jim Karlows Contribution After a struggle with suppliers for the parts for the conversion, I finally have a robust enough conversion to add LSB to the PRC-74 without allot of tweeking and fine tuning. I think now I can offer this to members of the group and be confident that, after installation, the conversion will provide a high level of satisfaction. The cost to group members is $ 35.00 plus $ 3.00 for shipping. Included are parts for the conversion, as well as a detailed instruction sheet to make the conversion. Total time to complete the job should be about 2 hours. The way the conversion works is as follows: The PRC-74 uses a 1750 KHz IF frequency. In the USB mode, a 1750 KHZ injection frequency is used to feed the product detector on receive, and to develop the USB IF signal through the 1750 KHz IF Filter. Because 1750 KHz Filters are nearly impossible to get, in the LSB mode, this conversion shifts the injection frequency to 1747 KHz. This is done by adding a small 1747 KHz crystal controlled DIP oscillator in available space in the frequency standard module. In the LSB mode, power is removed from the 1750 KHz standard and the DIP oscillator is turned on, providing the LSB injection frequency. In order to maintain correct dial calibrations when the mode is switched to LSB a small trimmer capacitor and reed relay are added in the synthesizer. In the LSB mode the relay is energized, switching in the trimmer cap which moves the synthesizer down 3 KHz, compensating the frequency synthesizer to maintain dial calibration in the LSB mode. The only cosmetic changes to the radio for the basic conversion is the removal of the two binding posts on the front of the radio. The "ANT" binding post is replaced with a BNC connector. The "GND" post is replaced with the LSB/USB switch. This is not a business for me,only a hobby. It is something I can share with other group members that will make the PRC-74 more fun to use. The price I charge just covers the costs for the parts, including the custom made DIP oscillators and reproduction costs for the instructions. I have about 5 kits left, with my current parts inventory. If more people are interested than I have kits, I will place an order for more parts. The DIP oscillators are the long lead item, with about 4-6 weeks required for delivery. Jim Karlow ed) While similar conversions of the PRC-74, and PRC-47 have been known of for some time, many(in the case of the PRC-47) and all( for the PRC-74) suffered from one major drawback. This was the shift of the displayed frequency on the radios dial when used in LSB, a real pain in the ass. Jim has succeeded in overcoming this common failing. He also has a completed design for the PRC-70, though it is possible that this one need be installed by him do to it's technical nature, but I don't know this for sure. Rumor has it,a similar design in the works for the GRC-106, I can't wait to see! ANNOUNCEMENT; PRC-74 Selectable Sideband, Jim has informed me that all the available selectable sideband conversion kits have been spoken for(see MCGP, May 21). He needs to know who all is interested in getting kits so he can place an order for the needed parts. If your interested contact Jim Karlow at *********************************************** RBS RUMINATIONS; By Hue Miller Around 1980 John Nelson and i tracked down the 10-year old rumor of a "place down by Lake Union that had stacks of TCS". Well, the place was a ship renovator who rebuilt small Navy ships into floating fish processors for the Alaska fishery. The place didn't have stacks of TCS anymore but they did have some RBS, RBM and RAK, RAL. We left with a stack of RBM and RBS, and some PSUs. As i recall this, i am reminded that this moment occurrs but once; so fill your trunk and sort it out later. Yes, i regret not grabbing everything. We found the equipment played right off; no crummy lytic caps to pop in these, they were ready to go 50 years later. IMO these models are mechanically excellent construction and architecture but electrically, sadly short of even the WW2 standard. The smallish but still boxy look, the excellent symmetric styling, good lighted dial, numerous controls, and well worked aluminum show a radio of real construction quality, if "soft skinned" and not bulletproof like most Navy ship gear. The Navy paid $1000 big WW2 bucks for each receiver, and R E Goodheart's ads called it "Navy's Pride". While this radio is EXTREMELY attractive to me, considering its great looks and moderate size/weight, consider: 1. the awful tuning speed. when you get a chance to try out a receiver new to you, do this: using a marker on the knob, like a spinner, a scratch, or setscrew, and another mark on the receiver panel, turn the knob and figger out how many kHz are covered by one spin of the knob. turn it multiple times and then divide, for better accuracy than just one turn. the RBS-RBM on top band, has something like 900 kHz per turn! this is absolutely, home table radio, shitty spec! 2. the IF is 1255 kHz, so the selectivity knob should really say "BROAD - EXTREMELY BROAD. of course, this had its purpose in its role as a non-primary-traffic receiver, as an auxiliary type receiver. however, if you try to listen to a crowded 49 meters broadcast band, or ham SSB, you will be very disappointed. these flaws are all the more disappointing when you look at the schematic and see the obvious intelligence of design and quality: 4-gang tuning capacitor, audio filtering, noise limiter, other features. So WHY did the Navy accept this receiver with a minimal gear reduction on the tuning??? I happen to keep basically only equipment that "pays its rent": i get a kick out of using it still. On this criterion i disposed of all my RBS and RBM-hf. NOW, here's more to the story. the RBM LF, CAY-46076, has the same mechanics BUT BUT BUT it only tunes 200 - 2000 KHz, AND.....the IF is 140 kHz. so, you actually have a good tuning speed, nice resolution on the dial readout, and actual selectivity. these are the ingredients of a real nice AM band dx'ers radio, or for working 160 meter DX, maybe teamed with a TCX xmtr. -------------------------------------------------------------------------------- Email Address Change, Re the name change: i have for many years thought the Cargo Cults of the So. Pacific were a pretty cool concept. apparently the last outbreak of this fervor was in some island rebellion around 1973; i think now with the information and drugging effect of the plug-in drug ( TV ) the thing is pretty much dead. According to __The Cargo Cult of the South Pacific__, the natives on some islands felt they made out pretty well by the Allied ( mainly US ) forces. A part of the supplies routed thru and expended on the islands ended up in native hands, as discards, trade earnings, or received as pay for labor: clothes, tools, canned foods, you name it. When the Allies withdrew, this rich ambiance faded, and the natives invented rituals hoping to conjure the return of the mythical black US GI "John Frum" ( probably a corruption of "John, from......." ) and the ships and planes again landing with their tons of good things. "....the natives drilled daily, using sticks for rifles.....they built 'wireless stations' with poles and wire as mock aerials....all these rituals to bring the return of the allies with their plenitude of cargo...." Hue Miller *********************************************** NAVY RBM SERIES; Good morning Dennis, Do you have anything in your E-archives about the RBM series of receivers? A MF,and SW version, along with 2 PS's and a control box arrived here yesterday (thanks to my swapmeet rooting!) How many of them were made, and about when, what they were used for originally, and whether they were any good for their intended application. I plan to restore them nonetheless (that's the joy in it for me) but would be nice to know what these old canoe anchors were all about. Someone modified the control box, but I believe I could de-mod it without too much problem. Know of any parts units? I could use a panel and a cabinet. (Salt damage, though the insides are nice and clean!) THanks !!! John Brewer --------------------------------------------------------------------------------- John, We have never featured the RBM series in any of our post, and as is typical of Naval WW-II equipment, the historical documentation is very limited. But I'll tell you what I can. Basically the RBM series were the Navy's equivalent to the Signal Corp's BC-312 family of receivers. While these receivers where completely different both physically, and electronically, than their Signal Corps counterparts, they were used in the same basic capacities as general purpose ground tactical receivers, designed to be used with various transmitters dependant on the purpose of the system. The most noted transmitter to be used with the RBM was the TBW which is considered by many the ground version of a GO-9 transmitter though packaging was completely different. The RBM/TBW would have been ruffly the equivalent of the Signal Corps BC-312/BC-191 combination, and used in the same type applications. In my opinion the Navy set was vastly superior, and this is typical of most WW-II Navy versus Signal Corps equipments. And in this light an Army/Navy debate might be in order for a future series comparing the equipment of the two services and the qualities of each(the Army will fail!). Two receivers where required to cover the frequency range of 200-2000kc, and 2mc-20mc. And depending on the installation in question, one, the other, or both receivers might be used in a system. Power supply options where considerably more varied than their Signal Corps counterparts by virtue of the RBM's use of an external power supply, a host of types being available to allow operation from just about any AC or DC source that might be encountered, even the use of dry batteries were provided for. An extremely long list of accessories were also available to enhance the radios operation in just about any conceivable role. Six versions of the RBM's were built in very large quantities from 1939 till 1944, and while they are not that rare, they are not as common today as the Signal Corps types, with the RBM-5 being the most often found. The first known order was placed with Stromberg-Carlson in March 1939 at a cost of $1200 including spares. Successive orders with that company took place in February 1940(RBM-1), December 1941(RBM-2), and December 1942(RBM-4). The last contracts were filled by Westinghouse in September of 1943, and March of 1944(RBM-5). Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN *********************************************** (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, ***********************************************

                                      Continue with Backmail 60
                                           Return Backmail Index