Military Collector Group Post

Backmail #50

    Index: US MILITARY PORTABLE RADIOS; PART I, By Alan D. Tasker WA1NYR US MILITARY PORTABLE RADIOS; PART II, By Alan D. Tasker WA1NYR US MILITARY PORTABLE RADIOS; PART III, By Alan D. Tasker WA1NYR US MILITARY PORTABLE RADIOS; PART IV, Conclusion By Dennis Starks US MILITARY PORTABLE RADIOS; Discussion US MILITARY PORTABLE RADIOS; More Discussion BURNING QUESTIONS; *********************************************** US MILITARY PORTABLE RADIOS; PART I, By Alan D. Tasker WA1NYR This is the story, as best I can tell it, of the progress that the U.S. Military has made over the past sixty years in mainstream portable voice communications radios. A "Portable" is defined as a unit capable of being operated while a person is in motion. Mainstream is defined as having reached some fair production level. Not included in this discussion are code sending units/beacons or satellite communication units (these are datacom only, i.e. e-mail, maps, etc.). Also included here is some information on non-mainstream products. In any work such as this, there is a tendency to pigeonhole items in an attempt to organize and simplify. This, plus the fact that one is always working with incomplete information, may lead to some inaccuracies. If you find something with which you do not agree or if you have something to add, please contact me. If you are unfamiliar with military nomenclature, you might want to visit references 6 and 12 first. Pictures for many of these radios appear in various web sites, and these are so indicated in the "Sources" section. General Goals In general, the goals in the development of new radios were, for many years, as follows (some of which are interdependent with, and some of which are contrary to, some of the others). Lower Power Consumption Smaller Size Wider Frequency Coverage Closer Channel Spacing Synthesized Frequency Operation Higher Reliability In more recent years, additional goals have been imposed. Internal Comsec (ICOM) Data send/receive capability along with voice In addition, there has sometimes been at least a perceived need to develop radios that operate within more than one band (i.e. the AN/PRC-70, 113, 117D, 128, 138, 139, and the AN/URC-100 series). These radios help "interoperability" with other fighting force elements, as well as communications with local elements when they exist. The Simple Six One can group the types of portable radios the Military buys into the following six categories, four of which are tactical and two of which are non-tactical. Not every service purchases all types, nor are all types procured in the same quantities. Tactical 1. The Squad Radio, VHF FM (wide band), a small hand held unit for very local communications within ground forces. 2. The main ground force communications device, a VHF FM (wide band) backpack, for longer distance communications than the squad radio can provide. 3. An FAC (Forward Air Controller) radio, generally a backpack, UHF, AM, for communications with aircraft. 4. A Special Forces radio, HF, SSB, backpack/manpack, for very long distance communications. Non-Tactical 5. SAR (Search and Rescue) radios, originally on 140.58 MHz, then 121.5/243 MHz, then 243 MHz only, and then multi channel, all AM, for downed airmen or other rescue duties. 6. Guard Duty/Fire Rescue/Other Use types, generally Low band (30-50 MHz) or High Band (152-174 MHz), or UHF (450-470 or 512 MHz), and/or the closely associated Government frequencies, narrow band FM. The Charts The following seven charts along with the introductory paragraphs for each summarize these six types of portable radio sets from the beginning (just before World War II) to the present. Your comments are welcome and are encouraged. Trends Over the years, certain trends have been evident. For instance, the Air Force and Army have tended to collaborate and use the same hardware when both services needed the same function. This can be seen in the charts, especially in SAR and non-tactical radio usage. Other trends are as follows. The Army has traditionally been the Lead in the Squad radio, although th e Marines started the development of the PRC-68. The Army is also the Lead in the VHF backpack area. The Air Force has traditionally been the Lead in the UHF FAC area with the Navy and Army tending to use what was developed. The notable exception is the PRC-75, which was developed for the Marines only. Additionally, there is little evidence to suggest that the Army has had a need for a UHF FAC radio later in time than the PRC-41 era. The Army generally Leads the effort in HF radio development. The Air force is currently the Lead in SAR system development. The Air Force is the Lead in the Scope Shield program, which is essentially non-tactical. The Beginning Steps in Ground Force Portable Radios, Pre WWII-Charts 1 and 7 The style developed in the beginning (battery on the bottom, rigid antenna on the top, front panel controls) was employed for the SCR-194 and SCR-195 for the Army and the TBY for the Navy. These were not really hand held devices, nor were they built like the backpacks with which we are familiar today. It is a tossup where to put these early units, so I simply put them in the charts with the most room. The VHF Squad Radio, WWII to Present-Charts 1 and 7 The first unit, the SCR-511, was designed to be used while riding a horse. However, the cavalry was abolished before WW II, so it would seem it was a bit awkward to use on foot. Therefore, the honor must go to the SCR-536 for being the first true handheld radio. (Both units were made, in the beginning, by Galvin Mfg. Co, which is now Motorola.) Packing a walloping 36 mW of Tx power, and subject to all the interference the HF AM band musters, it was none the less a success. The Navy's MAB and DAV were also fairly small units, but not quite handheld. The Korean War vintage PRC-6 (although there is some debate as to whether it made it through development in time to actually see wartime service), making use of the relatively new sub-miniature (pencil sized) tubes, improved greatly on the SCR-536. A VHF unit with 250-mW output, the FM mode of this unit reduced the interfering noise level greatly. After a long and drawn out research effort (basically waiting for transistor and integrated circuit technology to develop), the PRC-68 was produced, a very neat little package indeed. There had been an interim stop at the PRR-9/PRT-4, the first all solid state implementation, but they never really saw much use. The PRC-68 was to prove to be the father of 6 additional designs, the 68A, 68B(V), 68B(V)2, 126, 128, and 136. The 1" longer PRC-68A followed, which was one of the first microprocessor-controlled units. It allowed random frequency programming, but you had to stay within one of the four sub-bands. The present unit, the PRC-68B(V) (Marines)/PRC-126 (Army) is basically a PRC-68A with a frequency display. In addition, the PRC-126 has external frequency setability. They are microprocessor controlled and allow more latitude in channel placement than even the PRC-68A because they have an external antenna tuning control. The VHF Backpack Radio, WWII to Present-Charts 2 and 7 By all accounts, the first true backpack, the SCR-300, was a very successful design. It was followed by the Korean War vintage (although they may have just missed actual war service) PRC-8, 9, and 10 (Armor, Artillery, and Infantry respectively). Using sub-miniature tubes, these offered wider frequency coverage than before. The PRC-25 was the first synthesized unit, offered wider yet frequency coverage, and had just one tube (RF power output stage). Over 125,000 were produced. The all solid state but otherwise identical PRC-77 followed. The current unit is the PRC-119 SINCGARS (SINgle Channel Ground and Air Radio System). It has an ability to FH (Frequency Hop) in order to avoid jamming. In addition, the "A" model is called ICOM (Internal COMsec). Comsec stands for COMmunications SECurity, i.e. voice scrambling in order to prevent intelligent interception of message content by the opposition. This model also sports a much longer battery life. Meanwhile, there is an improvement program underway that has developed and purchased a small number of trial radios. The following was taken from the WWW (reference 18). "The Single Channel Ground and Airborne Radio System (SINCGARS) SIP (SINCGARS Improvement Program) Compatible Portable Radio, the RT-1753(C)/U, is a compact portable version of the SINCGARS SIP radio. This portable radio will be used along with the Lightweight Internet Controller (LINC) and Dismounted Soldier Unit (DSSU) in TF XXI (Task Force XXI) to support dismounted soldier operations and is designed to operate from a dismounted soldier's vest pouch. The radio replaces the current manpack version of the SINCGARS radio. The portable radio includes all SIP performance enhancements to include additional data mode features, embedded COMSEC, an external RS-232 Data Interface and packet switching for access into the tactical Internet. The radio weighs no more than 5 pounds (with battery and antenna), is approximately 1.9 inches by 10.6 inches in size (with battery) and provides selectable output RF transmit power up to two (2) watts and communication range of 3 to 4 kilometers. The portable radio uses a rechargeable NiCad battery pack. Battery life is approximately 6 hours. The portable radio shall consist of a portable radio, an antenna, and battery pack." *********************************************** US MILITARY PORTABLE RADIOS; PART II, By Alan D. Tasker WA1NYR There are a number of instances where the portable RT (Receiver/Transmitter) unit forms the basis of a number of nomenclatured systems (i.e. AN/PRC, AN/VRC, AN/GRC, etc.). The RT unit can, for instance, be attached to a vehicular mount that allows it to run on vehicle supplied power. Usually there is also an associated vehicular mounted amplifier that boosts the transmitter power, and boosts audio power as well in order to drive a speaker. Some of these systems even have a "jerk-and-run" capability, i.e. a quick way to disconnect and turn the RT into a portable again. In a similar vein, there is an older concept where communication devices that have a primary application (mounted in a vehicle perhaps) have also a "Secondary Application" as a manpack (larger than a backpack) portable. These devices, when attached to the correct backpack frame, and when connected to the correct battery box with the correct cables, became portable. The following is a list of these types. There may be others. TBX, 2-5.8 MHz SCR-284/BC-654, tunable, 3.8-5.8 MHz AM, replaced by SCR-694/BC-1306, tunable, 3.8-6.5 MHz, replaced by AN/GRC-9, tunable, 2-12 MHz. SCR-510/BC-629, two channel, 20-27.9 MHz FM. SCR-610/BC-659, two channel, 27-38.9 MHz FM. SCR-619/BC-1335, two channel, 27-38.9 MHz FM. RT-70/PRC-16, tunable, 47-58.4 MHz FM. The UHF Backpack for FAC (Forward Air Control)-Chart 3 Before the Military Aircraft Band changed to UHF, it was located in mid VHF, 100-156 MHz. The Navy had a 10 channel portable called the MAW. The Army had a two channel unit called the AN/TRC-7 which, apparently, in some applications, was portable (secondary application). With the growth of civilian aviation and other services following WW II, there were some revisions made to the frequency band allocations. The Military Aircraft Band changed to high VHF/low UHF, 225-400 MHz. The first portables to cover this new band were the MAY (Navy) and the AN/PRC-14 (Air Force/Army); both four-channel crystal controlled units. The MAY was a manpack unit, while the PRC-14 consisted of two main parts, a transceiver worn in the front, and a power supply with internal battery worn on the back. They were connected with a cable, and the antenna was mounted on top of the helmet. The synthesized (full band coverage) and partially transistorized PRC-41, another manpack unit, followed the PRC-14. There was an effort by the Air Force during the mid 60s to develop prototype FAC units that would operate on all three tactical bands plus VHF Air. Rather than being a single radio with four bands inside, they were actually four separate radios, each with its own battery, fastened together on a frame, but arranged so they could be separated and operated independently if desired. Sylvania developed the PRC-71, while Bendix developed the PRC-72. Some number of units were produced (my guess is about a hundred or so) and tested in Vietnam. They hit the surplus market in the very early 70s, so their short life indicates to me a certain lack of success (too big, too heavy???). Later, there was a definition of a better system, the PRC-82, with the four bands designated PRC-83 through 86. All four radios were to be synthesized (the PRC-72 HF section was the only synthesized unit in the previous efforts, all the others were channelized with 2 to 6 channels). It appears that the PRC-82 venture never proceeded too far either. Next, the Air Force developed the AN/PRC-66; a conventional backpack mounted unit. The Marines evidently did not want a backpack (perhaps because they envisioned an FAC with a PRC-70 (HF/VHF) or 77 (VHF only) on his back), so they went for a two piece design called the PRC-75. The radio and battery box fit into a two pocket front (belly) mounted canvas harness, and were connected with a cable. Both the 66 and the 75 were all solid state Collins Radio (USA for the 66, Toronto for the 75) designed units employing transistors, ICs and hybrid circuits to effect as small a size as possible. Today we have the two-band Navy/Air Force PRC-113(V)3, which covers both aircraft bands. It allows for Air-band interoperability wherever you are, and whomever you are working with. HF Backpacks for the Special Forces-Chart 4 There is not a lot of information on early HF units, such as the crystal controlled PRC-52, 62 and 64. There is some evidence to suggest that some or most of the PRC-64 units (Delco)(a Special Forces replacement for the GRC-109) were converted to the PRC-64A variant that had an improved interface to the GRA-71 burst keyer (300 WPM)(see references 6 and 17). It would appear that the first unit to reach widespread use was the partially transistorized (four tubes) synthesized AN/PRC-47. It is actually a two man portable (the second man carried the separate Silver battery in its case, amongst other things) with quite an antenna system for the occasions when a temporary fixed station is called for. The all-solid state PRC-74 with its variants 74A, 74B and 74C backpack units followed this. The dual band PRC-70, born out of the PRC-42 research effort, appeared next. It does not appear that it ever completely replaced the PRC-74. It also appears there are still PRC-47 and 74 units in the field. The current HF unit is the IHFR (Improved High Frequency Radio) AN/PRC-104, with variants "A" (changed to LCD readout) and "B" (which added provisions for STAJ, Short Term Anti Jam). Rumored to be on the horizon is the "Joint Tactical Radio." SAR-Rescue Radios-Chart 5, PRC, URC, UCMe The Search and Rescue function has produced at least eighteen different radio designs over the years, very prolific indeed. Intended to be packed with life rafts/boats, ejection seats, or, if small enough, with the airman himself, these units were generally powered by Mercury batteries because of the long shelf life of this particular chemistry. However, environmental concerns related to spent battery disposal have led the government to recently ban the further use of Mercury batteries in military systems. It looks like Lithium batteries will inherit this role. The Navy's AN/CRC-7 was the first two-way voice radio. Intended for life raft use, it may have been used by the Air Force as well. While in the midst of the aircraft frequency band plan change (see discussion in FAC section above), there was a need to have the SAR radios cover both 121.5 and 243 MHz. This made the radio rather large and heavy. The Air Force/Army went with the AN/URC-4 while the Navy went with the AN/PRC-17. In a personal interview with a SAC Airman during this time frame, he stated that the mass of the radio was so large, and the jerk of the parachute opening so great, that "the radio and its battery ripped through the vest and kept on going upon chute deployment." When the switch in frequencies was completed, the Air Force/Army went with the URC-11, while the Navy used the PRC-32. Both of these operated on 243 MHz only and were much smaller than their two frequency predecessors. Since they still employed sub-miniature tubes, the battery was still big and heavy, however. The push for a solid state unit resulted in the URC-10 (just one of many derivatives of the ACR designed RT-10) and the PRC-49. The Navy continued on and developed the ultimate in small size85the PRC-63, the cutest little thing you ever did see. However, the age of single frequency SAR radios had come to an end. The number of ELT (Emergency Locator Transmitter, sometimes automatically activated upon chute deployment) beacon transmissions crowding the 243 MHz frequency during battle in Vietnam proved the need for a second voice frequency, ultimately chosen to be 282.8 MHz. (In addition, at least some of the ELTs were eventually moved to 240.1 ??? MHz.) The Air Force developed the URC-64 four-channel device. The Army opted instead for the URC-68, a four channel two-band (VHF/UHF) radio that allowed downed airmen to communicate directly with ground troops as well as aircraft. Both of these were ultimately replaced by the Navy developed and improved PRC-90-2 two-channel unit (243 and 282.8 MHz), the first tri-service SAR radio. This was followed by a COTS (Commercial Off The Shelf) device from Motorola, the PRC-112. Sporting five different frequencies, circuitry was included which allowed equipment in the SAR aircraft to develop range and bearing information (DME), certainly a great help in aiding rescue efforts. The big news today in SAR is CSEL (Combat Survivor Evader Locator); a new Air Force managed tri-service program being run through Boeing. Racal has the contract for the new radio, which carries the nomenclature AN/PRQ-7. It will be capable of transmitting on at least 121.5, 243, and 406.025 MHz (the COPAS-SARSAT satellite tracking SAR system). It will also receive GPS information. Meanwhile, Motorola produced 1000 pieces of an interim solution for use in the hot spots around the globe. It is called the HOOK-112, and it is a PRC-112 with an internal GPS (Global Positioning System) receiver that encrypts location data and transmits it upon demand to the SAR aircraft. Non Tactical Portables-Chart 6 There have been a number of non-tactical portables used over the years. For the most part, these have been commercially available units (i.e. Motorola, Comco, Repco, Bendix, etc.) provisioned by the services for use all over the globe, and operating generally in the NBFM mode within some part of or all of one of the following bands8530-50 MHz, or 132-174 MHz, or 406-470 MHz. Additional numbers known to fall in this category are the PRC-23 and 24 (Army), 29 (Navy), and 59 (Coast Guard). Unfortunately, except for the PRC-127, information on this class of portables is scarce. The Scope Shield program (AF run tri-service) is an exception. The second effort at providing a radio that would be interoperable with standard commercial frequencies made use of the AN/PRC-126 but changed the circuitry so that either 30-88 or 130-174 MHz could be covered by exchanging modules. This unit is the AN/PRC-128, and is an outgrowth of the early Scope Shield efforts with the PRC-68B(V) low band (the Marines also bought this one for tactical purposes) and PRC-68B(V)2 high band separate radios. (The PRC-136 fire rescue set appears to be another derivative of the PRC-68/126 programs.) The Scope Shield II Program then developed the AN/PRC-139 with Racal. This radio can cover all three bands with module exchange, VHF low, VHF high, and UHF, all NBFM. *********************************************** US MILITARY PORTABLE RADIOS; PART III, By Alan D. Tasker WA1NYR Multi Band Portables There has been a trend to develop, for some applications, tactical portable radios that cover more than one tactical band. The list is as follows. 1. The first was the AN/PRC-70, chart 4. It covers the HF spectrum as well as the Tactical VHF frequencies. Harris' PRC-138, chart 4 also, is a more modern type covering these same two bands. It is in use by U.N. Land Force Elements. 2. The already mentioned AN/PRC-113, chart 3, covers both the VHF and UHF aircraft bands. 3. The Scope Shield Program developed PRC-128 and PRC-139, chart 6. 4. Harris developed the PRC-117D, which covers the Tactical VHF (low) band, VHF high band (aircraft and mobile) as well as Tactical UHF (including SATCOM), chart 2. Note: SATCOM is effected using FM within the 225-400 MHz military aircraft (generally AM) band. The Marines and the Seals are apparently using some number of these radios. 5. The Motorola developed AN/URC-1xx series, chart 7. These are two band radios, all of which include the tactical UHF (AM) frequencies, including SATCOM (FM) as the first band. The second band can be tactical VHF, or high VHF, or ??? The Army is apparently using some number of the URC-100 for voice and the URC-110 for data. The Navy Seals apparently have some number of URC-110 sets also. Unknowns There are a lot of AN/PRC-XYZ numbers unaccounted for. Some of these were concepts that never made it further, while other programs may have made it to the prototype stage. Still others may have been limited fielding trials of a particular device to test it out. The following numbers have appeared on real hardware, but the story behind why remains a mystery to me. Surely, somebody out there knows the story. Although the PRC-117 and URC-1xx units are described above, this is only the "what". The "why'" remains elusive. PRC-116, the Racal Jaguar V, 30-88 MHz ECCM unit, Racal #BC-66H PRC-124, a Collins MP-83 TRC-77 HF rig Battery Technology Where there's a portable, there's a battery. They come in two classes, Primary (use it once and throw it away)(nomenclatured BA-xxx), and Secondary (rechargeable)(nomenclatured BB-xxx). The bottom line is that primary batteries offer longer life per use, but of course, they can't be recharged. During WWII, there were only three types of batteries used in portables, Lead Acid rechargeable (for units with vibrator power supplies), Carbon Zinc for most of the rest, or Mercury (rescue radios only). Today, there are a bewildering number of chemistries out there, including but not limited to the following. Primary Alkaline, certainly low cost. Magnesium, on the scene until Lithium came along. Lithium/Sulfur Dioxide, the king of the hill for now. Secondary Lead Acid, liquid, gel, or starved electrolyte types, old venerable but heavy and has a tendency to sulfate. Silver, stayed for a short time. Nickel-Cadmium, lighter weight but has memory effect, usage is fading. Nickel Metal Hydride, twice the energy density of the NiCad, and with no memory effect, but expensive. Lithium Ion may be coming soon. The goal is to obtain the highest energy density (watt-hours per unit volume (cubic inches)) at the lowest possible cost. Unfortunately, some of the highest performers are also the most expensive. However, some work over the past few years in Lead Acid technology has shown that proper charging techniques (pulse) can forestall sulfation, the chief cause of failure in this cell chemistry. Apparently, the increase in life can be up to 10 times. For a cash starved Military, this could be a Godsend. One of the unfortunate characteristics of secondary batteries, however, is that most if not all of them have a self discharge rate of 1-3% per day at 25 degrees C, worse as it gets hotter. References and Other Sources of Information (in no particular order) 1. The Technical Manuals of the Individual Radios Listed, and other general Military documents. 2. "History of the Squad Radio", Marvin W. Curtis, US Army Electronics Command, Report # ECOM-4451. 3. "The Army in World War II", "The Signal Corps", a three volume set. 4. Various news articles published by the Armed Services over the years. 5. Richard Lacroix (PRC-25, 77, 66, 68,126, 70,104, and Canadian types PRC-515, 521) (http://web.globalserve.net/~rlacroix/radspec/radspec.htm ) 6. Tom Norris (The Mil Commo Equip List) (http://www.telalink.net/~badger/millist/mi.html ) 7. David Ross (TBY, PRC-14, 38) ( http://www.hypertools.com ) 8. MRCG (SCR-536/BC-611) (http://www.calpoly.edu/~doragsda/mrcg.htm ) 9. Joseph W. Pinner, KC5IJD 10. Dan Foglton 11. Kurt Lesser 12. The U.S. Army Signal Corps Museum (SCR/BC info) (http://www.gordon.army.mil/museum/) 13. Information on "The Web", such as battery data, Signal Corps info on the AN/PRC-104, 126, 127 (drawings), AN/URC-100, 110, and SINCGARS, Marine Corps info on the AN/PRC-113 and 136, Navy Seal info on the AN/PRC-117, AN/URC-110, Air Force info on the Hook-112 and CSEL SAR programs and the Scope Shield Program, UN info on the AN/PRC-138, the COPAS-SARSAT satellite tracking SAR system, the web sites for Motorola, Harris, Racal, Fair Radio Sales, Toronto Surplus, and Mike Murphy Surplus listings. 14. "U.S. Military Combat Aircrew Individual Survival Equipment, WWII to present, a reference guide for the collector", Michael S. Breuninger 15. ECOM reports #0319-1 and 0319-4, first and fourth quarterly reports on the development of Radio Set AN/PRC-70. 17. Steve's Green Pages (PRC-64A) ( http://www.users.bigpond.com/SHILL/ 18. SIP (SINCGARS Improvement Program) Portable information; see the following URLs and some of their links. (http://jointventure.monroe.army.mil/dbpages/INIBATT335.htm#topics ), (http://www.gordon.army.mil/dcd/tfxxi/htmlgta/gta-toc.htm ), (http://www.monmouth.army.mil/cecom/lrc/forcexxi/comm/sigsipgd.html ). 19. Pete McCollum (See the link to his write-up on the GRC-109, etc in reference 6.). 20. http://www.discworld.net/surplus/radio/PRC47.htm Charts listed in the text are available from the author via email. *********************************************** US MILITARY PORTABLE RADIOS; PART IV, Conclusion By Dennis Starks Forward: I realize that the author's intent in the first parts of this series was to give a casual account of the development of selected portable radios beginning in WW-II and progressing to the present. However things being as they are, and me being the ass hole I am, I just couldn't leave it at that. I felt that several things should be covered in more detail, and a couple half-truths dispelled. It is my sincere hope that further, more detail discussion may be the result of publishing this material. Comments from everybody, regardless of content are most emphatically sought. In The Beginning, The SCR-511 was not developed before the SCR-536, in fact, the SCR-536 was undergoing field trials before the SCR-511. As has been covered in great detail via this forum, the two radios were designed with two completely different intended purposes, it was fate that joined them as companions in the field. And the Navy had fielded the MU(early MAB) before the advent of either. Surely, it can be shown that the Navy has traditionally been far in advance of Army development all throughout radio communications history. Some examples, the Navy had in hand by 1939 the ART-13(ATC), TCS, TBY, TBX, TBW, MU and the famous Command Sets to name just a few. All far and away more advanced than their Signal Corps counterparts BC-375, BC-223, BC-222, BC-654, BC-191, BC-611, BC-229/230. It would not be until near wars end that the Signal Corps would catch up to the Navy and in some cases adopt Naval equipment. Similar examples can be shown to the present day. Perhaps a future series of articles entitled "Army Versus Navy" might be in order. These facts however have been neglected in history, and overshadowed by Army variants for several reasons. First is the secretive nature of the Navy which prevented the commercial propagandizing enjoyed by the Army and it's equipment. Second is shear numbers, while the Marine Corps had by mid WW-II a large selection of excellent equipment to choose from, their operational proximity to Army units by this time, combined by with the greater numbers of Army units and a difference in operational doctrines mandated that they(the Marine Corps) adopt and use those items of Signal Corps equipment most often needed to both enhance compatibility, and simplify the horrendous logistics problems associated with the support of such contingents in the field. Third was the support by manufactures at home. Manufacturing facilities at home were stretched to near limits. Every item needed to support the war effort had to compete for these facilities. The extent of this competition is very difficult to convey, but suffice to say it created extreme tension between ALL the services. It should also be noted that Army Signal Corps, and Air force development were one in the same thing until the split of the Air force with the Army well after WW-II. Until then the only development or procurement effected by the "Army Air Corps" on it's own and without Signal Corps consent or collaboration was met with later disaster. A case in point was the Air Corps Jefferson Travis field radio sets that were ordered out of defiance without Signal Corps consent. The Jefferson Travis was much like a larger, more powerful SCR-284(BC-654). Later during the North African Campaign, the Air Corps complained to the Signal Corps about the extreme weight of the radio set, and their difficulties in obtaining support and maintenance items. The Signal Corps replied in effect, this isn't one of our radio's, we did not order, nor approve them, therefore the logistic support channels do no exist in our system, I/E you shit your own nest now lay in it! The Jefferson Travis was then replaced in the field with Signal Corps types which had been designed for that same purpose rather than further clog up the logistic channels trying to support it. The same story can be re-told with several other examples. FAC Radios, The Air force lead in the development and use of an FAC radios can be debated in depth. Considering the WW-II developmental practices outlined above, the first true FAC radio was the TRC-7 of mid WW-II vintage, developed for Military intelligence, and Airborne troops(not the Air Corps) as both a liaison radio for air support, and later as a means of fighter control for extreme forward area ground troops. It was indeed a backpack radio operating from the same battery as a BC-1000, and provided with a very large array of accessaries that allowed it's use as a simi-fixed station, even a hand crank generator was available. There is also evidence to show that the CRC-7 (the first hand -held VHF AM downed airman's radio) had been used as an expedient by Airborne troops even before the advent of the TRC-7(more on the CRC-7 later). The mid-late 50's saw a re-emergence of the TRC-7 in the hands of the Air force. This as a result of the realization that our move to UHF AM for tactical air communications had left the rest of the world behind, thus American FAC teams had no means of communications with allied aircraft. This condition persisted until the end of US involvement in Vietnam, and a steady succession of radios were either developed or purchased Off-The-Shelf and used as expedients to relieve some of the problem. Long before the Army/Air force's fumbling along with the TRC-7, and PRC-14(late 50's). The Navy had realized a need and solved it by late WW-II. This with the MAY(UHF AM) and the MAW(VHF AM), both these radios were basically backpack types that could also be set for simi-fixed operation with an elevated antenna. Though grossly obsolete they would still be in the hands of Marine FAC/Pathfinder units until the late 60's. In the same light, the development of the PRC-41, and PRC-47 can be more closely credited to the Marine Corps who was by far the largest purchaser, rather than the Army or Air force. It should be noted that FAC operations have the peculiar need to be able to operate on all bands, I/E HF/AM(later SSB), VHF/FM, VHF/AM, and UHF/AM. This led to the Air force's development of the PRC-71, 72, 83 etc. None were built in very significant quantity. The Army, and Navy on the other hand chose to stick with an assemblage of the more common tactical sets PRC-25/77, 74, 47(Marines), and 41. In addition, history will show that virtually all the common radios originally developed as Downed Airman's, or survival radios, also saw secondary duty in use as a front line means of fighter control often in the hands of Special Forces Teams, and other Irregular Forces. These include the URC-4, 11, 10, 10A, PRC-63, 90, ACR-RT-10 and a long list of others. It is true that very little is known of the Pre-SSB days of the front line foot FAC units. We do know that the GRC-9 was used in this capacity while vehicular, and was most probably desmounted for close-in use. The possiblity also exist that the GRC-13 might have been used in this same role, and if so, might account for it's extreme rarity today. While the Marine Corps did have access to GRC-9's their TBX series remained in service at least until the end of the Korean War, and evendence exist that place it in use even later. It is very doughtfull that either the GRC-109, or the PRC-64 ever saw service in use by FAC units. This because the primary mode for both of these radio sets was CW, and voice communications were needed for spontaneous aircraft tactical coordination. Also the history of the GRC-109/RS-1 in military hands has been well documented via this forum and precludes any such usage. Another contributing factor in the development of FAC equipment is that Air force FAC units, unlike Army FAC's and Marine Pathfinders seldom advanced into the extreme forward areas that would require the use of backpack equipment. Thus most of the equipment used by them were vehicular in nature. Beginning in WW-II a tradition of retro-fitting aircraft radio equipment into ground vehicles started with the SCR-522 being installed in tanks as the SCR-524. This practice mushroomed after WW-II with 24vdc(compatible with 28vdc aircraft) becoming our military's standard vehicle voltage, and still lives on today, the variations of equipment used would fill several volumes, and include HF, VHF, and UHF examples of every type and vintage. PRT-4/PRR-9/PRC-68, It is true that there was a long drawn out research effort that resulted in the Marine Corps PRC-68. But this was preceded by an even longer effort to develop the PRT-4/PRR-9, beginning in 1950 and ending in 1964. This effort produced the experimental PRC-15, 30, 34, 35, & 36. While it is true the PRT-4/PRR-9 saw little actual service in the field, it remained the only official squad radio of record until at least 1977, when only experimental versions of the PRC-68 were yet available. The PRT-4/PRR-9 combination remains extremely significant to history for several reasons. First and foremost was the technology they represented including the first in an all solid state radio set, and second the use of a 10.7mc IF frequency which is now standard, and lastly the first use of an Integrated circuit(IC), this is the 150cps tone generator on "A" models. The story told in the development of these radios is an un-equaled example of Government Bull Shit, and non-cooperation. The PRC-68 was the direct result of the adoption of the PRT-4/PRR-9 and not because of any obvious reasoning. But out of the disgust felt by the Marine Corps having been totally ignored during the entire developmental process even though this was a joint services project. Their grievance was not with the basic design of the radio set, or it's performance, rather it was the dual radio packaging and limited channel capacity. I/E the Marine Corps had all along pressed for a channel capacity of at least four, and a radio housed in a single cabinet. Had their wishes been headed during the Development of the PRT-4/PRR-9, we might not ever have received the PRC-68's, or at least not until a much later date. In the interum years between the PRT-4/PRR-9 and the PRC-68, another long list of radios were developed, and or purchased as emergency expediants in very limited quantities. Some of the later include some international joint development units such as the PRC-601, and 602 a joint Isreali/US, Tadiran/GTE venture. At least four solid state versions of the PRC-6 are also known to have been purchased by the US government, two types of German origin, and two of US. Downed Airman's/Survival Radios(SAR), While their was a succession of survival type radios used before during and after WW-II, the first such radio adopted as a Standard Item was the legendary Gibson Girl of WW-II fame. A direct copy of a German set that had been captured in the North Sea by the British, then remanded by them to the US for development and production. It remained in service aboard large aircraft and all sea going vessels with very little change until the late 80's and the demise of the 500kc marine distress band, combined with the negating of Mores Code proficiency of licensed marine radio operators.. Second to emerge was the CRC-7. While it is true that the radio was used in life raft during the war. It's greatest claim to fame was it's use aboard fighter aircraft where the available space for such equipment was at a premium (the CRC-7 was a transceiver shaped like a large cigar tube, approx 2" in diameter, & 14" long). In postwar years it would receive expanded use in light bombers, and with commercial airlines. The Army/Air force/URC-4 use combined with the Navy/PRC-17 use can be debated to some extent as numerous examples of the URC-4 survive to show Navy use. In addition, most surviving examples of the PRC-17 show use by commercial airlines. Further, the URC-11/Army/Air force, and PRC-32/Navy associations can also be debated. It would appear that the Naval purchase of the PRC-32 was a simple expedient to augment supplies of their URC-11's at a time when technology was awaiting the advent of an all solid state radio. I/E, a limbo period existed between the URC-11(all tubes) and the first solid state SAR radio. During this period a long list of Make-Do radios were purchased, tested, or used. Some of these were even commercial Off-the-Shelf types including many ACR built variants. It should be noted that all these early SAR radios(except the CRC-7), even the first and second generation ACR types, used and external, metal incased, battery that was connected to the radio via an umbilical cable, making for a very cumbersome arrangement. The first solid state SAR radio was not the ACR-RT-10, or the URC-10(both being the same radio). The first model RT-10 was in fact a tube type radio and used a separate battery just as previous designs. The second version "A" model, though physically identical to it's older brother was indeed all solid state. It was adopted by all US services with various markings including ACR-RT-10A, URC-10A, and PRC-93. Apparently due to it's high production cost it did not fair well in military service. The Army's URC-68 was never intended as a one size fits all SAR radio. It was expressly intended for use by helicopter flight crews and with their close operational proximity to ground troops, the lowband VHF/FM band was included. At one time it was briefly considered by the Army Rangers as a "Stop Gap" radio to fill the void they felt for lack of a suitable squad radio. It was however quickly dismissed as too fragile for this type use. The Navy PRC-63, though it did enjoy some popularity and use, was a hermetically sealed Throw-Away radio. Built completely from synthetics it was very light weight, compact, and possibly for the first time in large scale, used a "Rubber Duckie" type antenna. But it's synthetic materials rendered it fragile, and it's being permanently seal prevented any attempt at servicing. It gave way in short order to the PRC-90. The Navy's improved PRC-90-2. The only difference between the PRC-90's used by the Navy/Marine Corps, and those in use by the Army/Air Force was in the process used to manufacture their cabinets. Both radio variants were built in the same factories at the same time, on the same production lines. the deference is in the type aluminum used in the cabinets on each variant. Those used by the Army/Air Force have an aluminum cabinet that began life as an investment casting. On the other hand, Navy/Marine Corps cabinets are completely milled from a solid block of aluminum. the end result of the Navy/Marine manufacturing process was a radio that would survive being submerged in water to a greater depth. Even by the late 50's-early 60's, the military had not completely weaned itself from some dependance on the VHF(Civil) aircraft band. The URC-14 is identical in every respect to a URC-11 except for one, it operates on 121.5 vice 243mc. This can be seen again with the current PRC-106, a radio which is physically identical to the PRC-90, except that this one is dual band and operates on both 121.5, and 243mc. Has anyone ever noticed the harmonic relationship between all the aircraft Guard frequencies? We have 40.5mc FM used in helicopters, times three equals 121.5 for the civil aircraft band, time two equals 243mc military guard. Coincidence? Back-Pack Radios, The BC-222/322(SCR-194/195) along with the TBY were indeed Backpack radios, and as such designed to be operable while in motion on the operator's back(though admittedly a very precarious operation for these particular radios). Followed by the SCR-300(BC-1000) which would set the stage for ALL front line tactical radios to follow, even to this day. The PRC-8, 9, 10, not only offered much greater frequency coverage with less signal bandwidth, and a smaller size and weight. But also introduced the first examples of modular design into a military radio. This greatly simplifying field service and logistics, and provided some measure if interchangeability between radio parts and accessories. The Canadians, Dutch, and Australians would ingeniously expand on this system in their same generation of equipment to include their Squad Radio, the CPRC-26. Which used common components, and accessories with not only their own versions of the PRC-8, 9, & 10, but also US radios. The US would not follow their own lead with our PRC-6 which included none of this interchangeability. Another "First" for the PRC-10 family of radios, and possibly most significant, was their Steel Tape antenna that would become an international standard to this day. The PRC-25 is the single most significant contribution to military tactical communication of it's type since the advent of the SCR-300(BC-1000). It and it's immediate successor the PRC-77 would become the most proliferate radio in military history spanning almost 30 years, 40 countries, and countless manufactures foreign and domestic. It would remain the standard for comparison long after it's obsolescence, and still remains in widespread use today. Besides being the first solid state FM backpack radio, it also introduced the now standard 150cps tone squelch system which effectively "Grunt Proofed" it not only simplifying operation by untrained personnel but also reducing front panel controls to a minimum. The PRC-119 is by ALL accounts, especially those taxed with it's operation, a horribly over complicated, and temperamental radio set. I personally cannot perceive it's longevity as a replacement for the PRC-77 excepted in higher echelons where communications security is of utmost importance and the personnel that are highly trained for it's operation, and support are available. Multi Role Radio Equipment, While the concept of a multi role vehicular/manpack radio system is indeed an old one, it still enjoys great popularity today world wide. And too, while it is true that such radios as the BC-654, 620, 659, 1306, GRC-9, TBX and a host of others, were adapted for use in a vehicular mode. Their primary design intent and purpose in life was as a Field Portable/Man-Pack radio set and not a vehicular one. In the case of the TBX, though power supplies existed which allowed vehicular use, no mounting hardware for either the radio or it's ancillary equipment were ever produced. Vehicular installation instructions for this particular family of radios amounted to templates by which plywood mounts could be cut. The reverse is true of such radios as the BC-1335, and RT-70 who's portability was secondary to their primary mission as a vehicular radio. Special Forces Portables, It is true that early equipment specifically designed for use by various Special Forces groups are hard to document, however much information has been gathered on both the earliest and latest sets to see their use, with only an interim gap between the GRC-109/RS-1, RS-6, GRC-9, and the WW-II PRC-5. The first and second radios to be developed for use by any US Elite Force were the PRC-1, and PRC-5. Both Classic Suite Case type radios, the PRC-1 arrived early in WW-II and is responsible for being the backbone of both tactical, and clandestine communication in the China Burma theater, not only by groups such as "Galahad, and "Merill's Marauders", but also the OSS Special Operations Group 101. Not the SSTR-1 which has received the credit for this activity. The PRC-5 arrived about mid-war, and while it's exploits are not documented at all, evidenced does exist to place it too in the China/Burma Theater. The BC-611(SCR-536) was also originally designed expressly for use by Airborne troops. But as we know, it was later used by virtually every service, and every Allied country, in every theater of WW-II.. The third known radio to have been designed expressely for Special(Elite) Forces was the BC-1306(SCR-694C). Being originally designed for use by Airborne and Mountain troops, it was later pressed into service with all branches of service due to the major shortcommings of the BC-654(SCR-284). The SCR-284 shortcomming were indeed so great, that simi-experimental versions of the SCR-694 were placed into early service, the BC-1136(SCR-694AW). At the same time SCR-694 became available, so too did the TRC-2. Originally intended for service with Military Intelligence, this was a combination of the a standard BC-1306 with it's lower frequency twin, the RT-12/TRC-2. Next came the already described TRC-7 also intended for use by Airborne troops, followed closely my the TRC-10. The later was a re-packaged version of the PRC-1 which allowed for a far more versatile operational package. At a glance, it was similar in appearance to the SCR-284 but boasted a much wider frequency coverage, and CW only operation. This radio today remains one of the rarest, and most difficult to document of all military radios. Somewhere in this mess came the PRC-4, about this radio we know nothing excepting that it was a discized version of the SCR-536/BC-611, also intended for use by Military Intelligence. The Army was not the only military organization to employ specialized radio equipment for it's Elite forces, the Navy too had such equipment even in the early days. However due to the typical secrecy vail that shrouded all Naval equipment, documentation of these types is the most difficult of all. Only two radios are known to have seen service with these type forces. The first was the common TBX who's exploits are only now beginning to surface. The second, also of WW-II vintage was the MBM. A suitcase-like radio set design for use by forward raiding parties. It should be noted that the Navy maintained clandestine operations in all Pacific theaters that were rivaled by no other organization foreign or domestic. And lest we forget the vulnerable MAB, or as it is called in it's own manual "the Para-Talkie", being pictured in used by a Para-Marine(though it is unkown whether the radio saw any use with this short lived branch of the Marine Corps). Post-War years saw the Army Special Forces using the CIA's RS-1, and the GRC-9. It was not until late 1962 that the RS-1 would be officially adopted as the GRC-109 and a regular Army Standard Issue item. And then only because of the transfer of operational control of the Army Special Forces from CIA hands back to regular Army. Contrary to popular belief, the GRC-109"A" model was not an adaptation for code burst operation. It was in fact the same radio supplied with a different "Armor" cabinet that was more than twice as thick as the previous model, with a corresponding increase in weight. By the time of the demise of the RS-1/GRC-109 they had nearly all been either supplied from the factory with code burst capabilities, or this feature was added by way of an MWO. Following closely the adoption of the GRC-109 came the PRC-64 in 1965. Again a radio of CIA origin via the Delco 5300. While the widespread use of the PRC-64 in US hands may or may not have been short lived, and is open for debate, it did enjoy extreme popularity in the hands of one of our few Vietnam Conflict Allies, the Australians and their Special Operations Group. With the introduction of the "A" model with enhanced code burst operation, it would appear that all or most previous, models where modified to comply to the newer radio's specs in the same is respect as it's predecessors the RS-1, and GRC-109. But before this, with it's beginnings in question(approx early 60's/late 50's) came the simi-experimental TRC-77. Receiving it's TRC designation via WW-II tradition, it too was originally intend for use by Military Intelligence, and Special Forces. However by this time, it's intended US constituency had become highly disillusioned with any high tech/new fangled contraptions. It was then relegated to use by South Vietnamese commandos who were extremely active against North Vietnamese coastal installations. We have also recently learned, via this group, of possible Australian use. The PRC-62, while for some years it was in question whether this radio actually existed, and the few surviving references to it were simple type errors or just wishful thinking. Recent events, again via this forum and our Aussie members have proven not only the existence of this radio, but also it's use by both the US and Australian militaries. The author makes mention of the PRC-52, and PRC-42. Both of these are new ones to me, and I'm most interested to learn more about them. In the mid 60's to early 70's, a long list of SSB radios were acquired for testing in South East Asia(over 200). Tracing them down has been close to impossible. Every day somebody comes up with another possible candidate. Suffice to say that their were many radios acquired and used by every involved service. Some to the extent they received almost Standard type acceptance. Some familiar names include AVCO, Huges, Southcom, Halicrafters, Harris(RF), Motorola, Collins any others. It should be noted that the use of HF communications equipment by Special Forces tactical units was primarily NOT to provide "very long distance communications", as the layman might understand it. While radios of this type were capable of long range communications when in competent hands, the primary mission of an HF portable in the hands of any front line tactical unit was to provide communications at ranges not possible with VHF FM equipment of the same type. I/E 1-5 miles for VHF/FM types, 5-10 miles for the HF types. These distances generally represent those that the unit in question might be separated from either it's next higher echelon, or companion units. Typical extremely long rang communications with this type equipment in Vietnam were on the order of 20 miles max. Off-The-Shelf-Security-Radios, Unfortunately, the author at the time of his writing the first three parts article, was not privy to this group or it's archives. The story of these "Off the Shelf PRC's" was told in an in depth multi part series by that title, again via this forum, and is still available from our back issues. There are also numerous other articles related to the topics in this series available from our archives. Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN military-radio-guy@juno.com *********************************************** US MILITARY PORTABLE RADIOS; Discussion -Dennis, Thank you for your comments. I hope to hear from others as well. I've changed the write up to incorporate your major points and to make other parts clearer. As other info drifts in, I will change again. I do have to correct one statement you made, however...The RT-10, RT-278/URC-10, and RT-278A/URC-10 are all solid state units. The following is from TM 11-5820-640-15 which covers all three sets. "Battery power is provided via an external battery [ed) -16 Volts] connected to the radio set by a waterproof cable (RT-278/URC-10 and RT-278A/URC-10) or by an integral battery pack (ACR RT-10)." There were two types of integral packs described...one where the back cover (K308) had to be removed and tossed and a new cover put on in order to replace the battery, and another where just the battery (K308A) was tossed (this is the type I have). It also says there are RT-10's in the field (Navy) that have a 1/4 wave antenna, and other units (Air Force) with 1/2 wave antennas. The manual goes on to say there were some circuit changes that differentiate the RT-278 from the RT-278A and RT-10. There is a schematic for the RT-278, and a second schematic for the RT-278A and RT-10 serial numbers below 6773, and a third schematic for RT-278A and the RT-10 serial 6773 and up. There's at least two versions of the RT-10 out there that are not crystaled on 243 MHz, The PRC-93 version of the ACR RT-10 had the mechanical volume control, and the RT-20. It's a USMC set and labeled 'Code 1'. The RT-20A was on 251.9 MHz, which is channel B of the training version of the URC-64 (URC-64(T)), is the only frequency in the single frequency training version of the PRC-90 (which is called PRC-90(T), and is one of the frequencies in the two frequency version of the PRC-90(T), 236 MHz being the other. An Air Force Equipment Specialist said it was for training. I would guess he was right. Alan ---------------------------------------------------------------------------------- I have several URC-10s (demiled). They do use a seperate battery like the URC-4 but they are all solid state. I have both the RT-278 and RT-278A. The radios look identical to me, inside and out. The sets I have were made by Bendix Radio and not ACR. Were there competing models for the URC-10? I also have a radio made by Chromalloy Electronics Division that is marked ACR/RT-60B? Ever heard of Chromalloy? This is a dual band unit that looks just like the URC-10 the battery slides on the back. On the PRC-68, I have a prototype that was made by Motorola about 1968. It is sort of sythesised. It is a single channel crystal controlled but all the crystals are included in the package. It uses a crystal oscillator/mixing scheme to cut down on the number of crystals required to cover the 30-76 MHz band. My radio is marked AN/PRC-68 Ser. No. 021, Naval Electronic Systems Command, Motorola Inc. Contract No. N0024-67-C-1427. Do you have any other information on the early development of the PRC-68. Tom Bryan ed) The variants of the ACR family of radios are indeed mind boggling. It would appear to me that the Government model "URC-10" was a spin-off of the manufacture's model number as it would not otherwise fit properly into the chronology of this type equipment, and this would not be the first instance of the practice. I stand corrected on the solid state nature of the early ACR-RT-10, however I do believe that the credit for the first solid state "SAR" radio should really go to the PRC-49(and it's several versions, another NAVY FIRST!) as I believe it pre-dates the ACR's. Another candidate for Oddball SAR radio is the KEL Corp. ASR-100, it used a side folding chrome plated telescoping antenna (ala portable TV set), was all solid state , used the same back-mounted battery as the ACR's, was dual band, had a volume control, & "squelch". The first Squelch control I've ever seen on such a radio. The one in my collection apparently came from Airforce service in a bomber, and It's last inspection was in 1982. Something that I'm at a total loss to understand is this lack of the before mentioned squelch control on all main line radios of this type, even some of those intended for FAC service on the ground. It would seem to me, not even considering operator comfort, that the incorporation of a simple squelch circuit would have at least increased battery life. Your experimental PRC-68 is the first surviving example that I have heard of. I would think that the PRC-68 designation would have been followed by either an (XC-#), or (XE-#) suffix to give us an indication of which generation experimental it was. I wonder if it resembles the pictures presented in FM24-24 1977, and the early Jane's manuals which are also in fact prototypes, though Magnovox was then noted as the supplier? I can tell you from experience that messing around with experimentals is only for the most masochistic of collectors! Chromalloy Electronics Division is a new one on me, and I would not be too concerned about your Bendix marked URC-10. They were most likely just a sub-contractor, or second source supplier(as required in most government contracts). I recently read a so-so article from Electric Radio about the URC-35(R-1051 family) where the author gave credit to Scientific Radio for the design of the set. Credit of course should have gone to General Dynamics. SI was simply a sub-contracted second source. The author's act was like giving Stewart Warner credit for the TCS vice Collins. ---------------------------------------------------------------------------------- Dennis, Finally getting around to back email etc after several weeks gone. The US Mil Radio series you posted was a nice piece of work, lots of neat bits of info. A few comments.... While looking for other stuff I found something that maybe related to the early WWII vehicular sets. Its a picture of an SCR-284 mounted in a jeep. The set is fore and aft on the curbside with power coming from a handcranked generator in front of the passenger seat. The radio is clear enough but its impossible to see if the genny is permanently mounted or just stuck in front of the GI doing the cranking. GRC-9s were the primary radio for the Marines during the Lebanon expedition back in '56 or '58. I had a conversation with one of the ex radio ops who served during that time. Those little PRT4/PRT9 sets got cannibalized back in the early '80s as the radios on an early RPV comm relay used in some interesting places, mostly sand covered. A friend gave me a new test/channel set up box for the sets which was passed on to list member Jay Coward. So..if you ever turn up what appears to be a model plane on steroids with PRR/PRTs in it you'll know where it came from. I'm still looking for past notes to find which of the bailout radios we used to build some "primary initial termination devices", low backscatter beacons to call the helo when the bad guys are coming. The model we gutted was Navy with 121.5 and 243Mc beacon tone and voice comm. I think the other source was AN/URT-33A junkers. This will show up as a small folding yagi with the electronics in the 'boom' Do you use the 2259 ant? Believe that I still have a set of related Collins ap notes. If y'all want a copy let me know, will find them. Ed Zeranski This is a private opinion or statement. home email: ezeran@cris.com ed) The SCR-284/Jeep/Hand-crank gen is a real puzzler, and first I've ever heard of such a practice. It sounds more to me like some sort of field expedient devised by some crafty radioman to operate a field radio while mobile without having the proper installation equipment. One of even more grandiose scale, during the exodus of allied troops from Burma during the early days of WW-II, SCR-299's(BC-610) were mounted in JEEPS! The GRC-9/Marines/Lebanon tale is one I'd like very much to learn more about. Get the ex-radio-operator, tie him in a chair, and get the hole story!! I don't even know what a "2259 ant" is. Field Portable repeaters are an interesting subject for which very little is known. Jim Karlow has some sort of set also composed of PRT-4/PRR-9 components into a single package. Years ago I had a most interesting set hand built by Motorola around a single standard PRC-25. It was a simplex repeater that operated using time-domain-sequencing. It really worked, and only had a very slight, almost non-detectable putter in the received signal. Dennis Starks; MILITARY RADIO COLLECTOR/HISTORIAN military-radio-guy@juno.com *********************************************** US MILITARY PORTABLE RADIOS; More Discussion SAR Radios Lacking Squelch, Reference: why no squelch on several "survival radios". The radios were designed to be operated by anybody, the simpler the better, having operated all most all of the units between 1960 and 1985, the simpler radios were always the best. You don't want to be using a PLD "personal lowering device" with one hand ,after landing in the top of a forest canopy and try to figure out how to operate a radio adjusting squelch etc. The reassuring hiss told you it was working and was ready.With the squelch open the units were very sensitive. The older radios of course were very broad banded and you could hear near by transmissions on frequencies close to 121.5 as the squelch was open. You saved battery power by only listening only at designated times or when it was obvious help was in the area. On the subject of batteries, two things I aways carried was extra ammo and extra batteries. The "survival radios" were used for many things, I've even used a URC-4 at a drop zone for giving information to in coming aircraft as to winds and clearance to drop, "green smoke" was always confirmed by radio if it was possible This was always done on a "training frequency" During land and sea survival training, the radios were always on a "training frequency". A reminder that some of your new members may not be aware is the use of 121.5 and 243.0 MCs, (I dont recognize MHz) 243.0 MCs was picked for the UHF frequency as it was the second harmonic of 121.5. Most of the first "survival radios" had a very strong second harmonic as they were "simple" in constrution. If there was any confusion, scratch that there was always confusion during a rescue, but anyway if you listened on 243.0 you has all the bases covered in the early days. The URC-4 was very popular to convert to two meters in the sixties, several articles appeared in CQ magazine. I have even used them on repeaters as they FM slightly, very low audio but still detectable. You can "slope detect" for receive. Great display item at shows. 73 Breck K4CHE ed) I concur the non-recognition of MHZ, you'll never see me using it. Also the lack of a squelch control on Downed Airman's radio or otherwise in the hands of ill trained personnel. But for use by highly trained FAC's it doesn't seem practical in radios designed for this purpose. The URC-4 was indeed a popular radio for conversion and use on 2 & 6 meters, as well as 220. The URC-4 was also converted to both 220 and 2 meters by many hams. --------------------------------------------------------------------------------- KEL, Motorola PRC-68, R-1051, Regard KEL ASR-100. Didn't KEL make the GE Pocket Mate for a while? That could explain the folding antenna. Regard experemental PRC-68. It is roughly the same size as the Magnavox unit but it has the antenna built into the base. There is also a provision for an external antenna. I used to own some of the prototypes that are in Janes, they are almost like the production unit execpt that the battery attaches by 2 studs that go through the battery rather than the clips on the side. Other than that the radio is identical to the production unit. They were marked XN or XE (can't remember which.) There are no "X" designations on the Motorola unit. Have you had a discussion of the R-1051/T-827/URC-35/GRC-106? I believe General Dynamics did invent it and the original set was the SC-901. The SC-901 is similar to the URC-35 (i.e. a receiver/exciter.) I was told that the original set was designed for communications among missile silos. Tom tbryan@nova.org ed) it is very possible your observed KEL/GE connection is so. The internal construction of the ASR-100 is VERY similar to the GE Pocket Com. I've heard the same story in regard the R-1051 family use in missile silos. I believe the origin was Jim Karlow, I wonder if we might impose on him to elaborate in detail. ---------------------------------------------------------------------------------- NVIS, Dennis, The AS-2259 is an antenna used with the PRC-47/104/etc for NVIS, near vertical incidence skywave, ops for 0-300 miles. I'll track down Pat Melly to see if will yak to a recorder about mid '50s Marine ops with the GRC-9 and the Lebanon deployment in particular. He was surprised I had the old radio gear and mentioned his using the GRC-9 with the leg key on the beach after their landing. By the way, Pat's experience in the '50s, the cannibalized PRT/PRRs, and the AS-2259 are some what related. Pat was using HF to comm with the afloat element for support etc. 25 years later the Marines were again in "The Root" but had VHF comms. Those VHF relays built using the PRT/PRR parts were to allow the Marines ashore and out of LOS with the ships or patrols blocked by cityscape to have comms. Beirut was not a friendly place and those interested should look for a copy of "The Root". The RPV/Relay was tested in the desert at 29 Palms then deployed. Research into NVIS for use with tactical radios got on a roll, and the Marines PRC-47 was a prime radio at the time. There was also work done on mobile NVIS from a Hummer and similar vehicles. The AS-2259 is one of the products from that era. I still have a co workers published work concerning the problem, math models, field test reports, and suggested fixes. Surprisingly, the study was not really followed up here in the US but was jumped on hard by NATO, especially the Germans, and also the Israelis who were faced with urban scenarios and had similar radios. Funny how stuff stays the same......Pat Melly actually had a better chance 25 years earlier. Then there is the story of the low visability antenna to replace the '1729 VHF vehicle antenna and the procurement follies...but thats another story. Ed Zeranski This is a private opinion or statement. home email: ezeran@cris.com ed) NVIS radiation is indeed a very interesting subject, and one I would have liked to elaborated further on in the article but didn't feel it appropriate at the time. Maybe you'd like to do something in-depth for us??? In a nut shell, the practice involves using inverse wave propagation and radiating an HF signal near to strait up. This signal is then reflected back to earth in an umbrella pattern providing effective short range communications with HF radio equipment where VHF equipment/communications were not suitable either because of range or terrain. I have had some interest & experience with this type propagation in both civilian and military applications. Perhaps I will cover it in more detail in a future article. *********************************************** BURNING QUESTIONS; -Anybody seen a real, in the flesh, PRC-103? -Is the PRC-96 still the prime Navy lifeboat rescue radio, or did it get replaced by the PRC-112 also? -The USMC used a version of the RT-10 called the PRC-93. It had a mechanical (shutter type) volume control, and was marked 'Code 1' Any idea what frequency they were on? -Was the PRC-68B(V)2 high-band radio ever produced? -What was a PRC-68(X)? PRC-68(L)? -What is the difference between a URC-104 and URC-111? -What is the battery number and voltage for a URC-64? -For the PRC-70, is there a TM 11-5820-553-35? If not, what is the maintenance manual number? -What is the difference between a PRC-75 and the A version and the B version? -What is the difference between a PRC-113 and the A version and the B version? -ELTs used to be mostly on 243.0 MHz. Rumor has it they moved. Did they? If so, where to? -What was a KEL something or other. Kel Com used to be a company here in the Boston area that was owned for a while by Bell and Howell. Did they make these? -Did they ever make any PRC-66 guard receivers? Alan atasker@ix.netcom.com *********************************************** (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)