|
|
01/02/07 |
       
|
U.S. Military Portable RadiosBy Alan Tasker, WA1NYR2/10/2000
Table of ContentsIntro IntroductionThis 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, with a concentration on the later, more convenient-to-use units (i.e. SCR-536/BC-611 and later, SCR-300/BC-1000 and later, i.e. units with integral battery packs). For completeness, there is a summary of earlier concepts in portable radio design on page 4. 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 clandestine radios (see reference 19), and only passing reference is made to code sending units/beacons. Satellite communication units (SATCOM is datacom only, i.e. e-mail, maps, etc.) are discussed only for those units that are dual mode, i.e. have provision for both radio communication and Satcom. Satcom only units (i.e. AN/PSC-xx) are not included here. Also included below is some information on non-mainstream products. The reader should note that this is a list of "what was" with some information on the "why and wherefore". Not generally included here is information relating to the success or failure of the individual radios in their intended application. 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 at [email protected]. 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. [And this website] General GoalsIn 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).
|
In more recent years, additional goals have been imposed.
 | Internal Comsec (ICOM), i.e. voice scrambling |
| 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 civilian elements such a police and fire when they exist.
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 |
| Non-Tactical |
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. A FAC (Forward Air Controller) radio, generally a backpack, UHF, AM, for communications with aircraft.
4. A Special Forces radio, HF, SSB, backpack/manpack, for longer distance communications than would be provided by the VHF Backpack.
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 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.
In recent 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 been the Lead in the Squad radio, although the Navy/Marines have contributed heavily. |
| 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, although the Army has the PRC-127 project. |
The style developed in the beginning (battery on the bottom, rigid antenna on the top center or side, 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, but were intended for backpack use even though they were not built like the backpacks with which we are familiar today
The first units developed that more or less conform to our present day expectations for handheld devices were the SCR-511 and the SCR-536. The SCR-511/BC-745 was designed to be used while riding a horse. However, the cavalry was abolished at the beginning of WW II, so it would seem it was a bit awkward to use on foot. It was, however, a marvelous example of good applied engineering, i.e. how to design a radio that was operable with just one hand while riding. However, the honor must go to the SCR-536/BC-611 (along with the SCR-585/BC-721 glider version) 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 still more or less a success. The Navy’s MAB and DAV were also fairly small units that operated in the same AM frequency band, 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 five additional designs, the 68A, 68B, 126, 128, and 136 (although this might prove to be a 128 high band only unit).
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 a PRC-68A with a frequency display and external frequency settability. They are microprocessor controlled and allow more latitude in channel placement than even the PRC-68A because they have an external antenna tuning control.
Chart 2 - VHF Backpack (use browser back key to return)
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, with a large quantity produced as well. Tone squelch (150 Hz) was introduced during this period (i.e. PRC-25 and later).
PRC-77 Clones
Although the PRC-77 design is not perfect, it did mark a milestone. It is an uncomplicated (therefor easy to use) wide frequency coverage all solid state unit that achieved a good reliability record in the field. As a result, there have been a number of manufactures who have built clones of this radio (i.e. uses the same accessories), some offering improvements such as 25 kHz channel spacing, selectable output power, and/or updated circuitry to improve reliability. Some of these companies are listed below. NOTE: Some of these PRC-XXX numbers are not official. Companies sometimes assign their own out of sequence numbers for advertising purposes, especially in trying to promote themselves as having a PRC-77+.
| NAPCO International of Hopkins, MN, which offers, |
| A 25 kHz kit for retrofit into existing PRC-77 units. |
| "HR" modules, i.e. a module set made with fewer parts, thus enhancing reliability. Modules are interchangeable with the old ones. |
| PRC-770, a PRC-77 built with the 25 kHz channel spacing. |
| DATRON WORLD COMMUNICATIONS (Datron and Trans World combined), Vista, CA |
| PRC-1077, a PRC-77 with 25 kHz channel spacing and selectable power output of 0.1, 2, or 5 Watts. |
| PRC-1088 This radio evidently started life as the Collins developed MP-83, which later became the PRC-124 (my guess, a losing entry in the SINCGARS competition). It offers 25 kHz channel spacing, adjustable power output, and internal frequency hopping circuitry. |
| TADIRAN, Israel |
| PRC-2077 offers 25 kHz channel spacing along with highly updated circuitry. |
After the AN/PRC-77
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."
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.
Older Concepts
In a similar vein, there is an older concept where communication devices that have a "Primary Application" also have a "Secondary Application." Examples of primary and secondary applications are as follows.
| Mobile use |
| Portable use |
| Transportable use |
Sometimes there was only one use. In any event, all radios shown in the following list could, when attached to the correct backpack (rucksack) frame, and when connected to the correct battery box with the correct cables, turn into a useful portable. There may be others.
| SCR-510/BC-629, two channel 20-27.9 MHz FM. |
| SCR-610/BC-659, two channel, 27-38.9 MHz FM, replaced by |
| SCR-619/BC-1335, two channel 27-38.9 MHz FM. |
| RT-70/PRC-16, 47-58.4 MHz FM, tunable |
| RT-53/TRC-7, 100-156 MHz AM, 2 channel (there may not have been a frame for this one) |
Additionally, there is a closely allied type of radio that is almost portable, and is defined as transportable (by one or two men), and must be set up to operate. These are sometimes called packsets or manpacks (Note: "Transportable" was defined slightly differently in WWII.) Some of these have additional applications as discussed above. Examples of these are as follows.
| TBX, 2-5.8 MHz AM/CW, Tunable (Tx optional crystal controlled) |
| SCR-178/179/BC-186/187/188, 2-5 MHz AM/CW, tunable |
| SCR-288/BC-474, 2.5-6.3 MHz AM/CW, tunable |
| SCR-284/BC-654, tunable, 3.8-5.8 MHz AM/CW, replaced by |
| SCR-694/BC-1306, tunable, crystal option, 3.8-6.5 MHz AM/CW, replaced by |
| RT-77/GRC-9, tunable, crystal option, 2-12 MHz AM/CW, replaced by the RT-671/PRC-47 (see chart 4, a packset even though it has a PRC designation) |
| GRC-109 (T-784, R-1004, PP-2684 or 2685), 3-22 MHz CW Tx, AM/CW Rx, 1 channel, more of a clandestine set but mentioned for completeness as it has a military designation |
| TRC-2, 2-3.4 MHz AM/CW (RT-12), tunable, crystal option, plus included a BC-1306 |
| RT-46/TRC-12, 2-12 MHz CW, Tx 1 ch, Rx tunable |
| RT-654/TRC-77, 3-8 MHz CW Tx, AM/CW Rx, 6 channels |
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 in one of its intended applications operated as a portable (using the batteries developed for the SCR-300/BC-1000).
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. (It should be noted that foreign countries did not necessarily ever change over to the UHF band, making communications with their aircraft difficult when they were fighting with you.) 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, but in only 100 kHz steps) 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 75, Toronto for the 66) 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 with whomever you are working.
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."
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. It looks like Lithium batteries will inherit this role.
Many of these radios have seen service in roles other than SAR. Their small size lends itself to specialized communication duty, as evidenced in many of our conflicts, especially Vietnam.
It should be mentioned here for the purposes of completeness that the first life raft rescue radio was a code-sending transmitter nicknamed the "Gibson Girl". Nomenclatures included the BC-778 (SCR-578) and the AN/CRT-3. At 500 kHz it needed a long antenna, so it was furnished with both a kite and a balloon to loft the long wire. A chemical kit made hydrogen to inflate the balloon.
The Navy’s AN/CRC-7 was the first two-way voice radio. Intended for life raft and other uses, 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 both that and 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 that as well and also developed 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 radio resulted in the URC-10 (just one of many derivatives of the ACR designed RT-10 (243 MHz), such as RT-20A for training, (251.9 MHz), PRC-93 for the Marines (? MHz), and the RT-60 (243/282.8 MHz)), which saw use by all branches, and the PRC-49 Navy developed unit, which most likely was the first all solid state rescue radio to make it into service. The Navy continued on and developed the ultimate in small size…the 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.
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 for the OV-1 aircraft and for helicopters. It allowed downed airmen to communicate directly with ground troops as well as with aircraft. Both of these were manufactured by Magnavox, and were ultimately replaced by the Navy developed PRC-90, and improved PRC-90-1 and then -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 (AN/ARS-6) to develop range and bearing information (DME), certainly a great help in aiding rescue efforts.
Current Para-Rescue (in the water, voice or chin activated) radios include the PRC-103 AF unit, a spin off of the PRC-90, and the PRC-125 for the Navy. The current Naval lifeboat radio is the PRC-96. All units mentioned in this paragraph (and maybe even the PRC-106) were first designed by GTE/Sylvania, although most were produced by others, especially after GTE’s decision to exit this business segment.
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 COSPAS-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.
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 bands…30-50 MHz, or 132-174 MHz, or 406-470 MHz. Additional numbers known to fall in this category are the PRC-23, 24, 29, 39, 46, 55, 56, 58, 59, 61, 97, 101, and 129. Unfortunately, except for the PRC-127, information on this class of portables is sometimes scarce. Some facts have recently come to light, however, and the chart will be updated in due time.
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)(10 channels programmable with independent Tx and Rx frequencies if required, 2.5 kHz steps, NB or WB as required) 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.
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.
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, a PRC-77 type with 25 kHz channel spacing and FH. |
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. |
| 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)
The proceeding is an updated version of an article that originally appeared in 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 as long as the proper credit to the original author(s) and publisher (or the group) is included. For more information concerning this group or membership, contact Dennis Starks at….
[email protected].
Comments by Dennis Starks-Note: The above write-up has been changed to accommodate Dennis’ comments
The article was published in the Military Collector Group Post. The editor gave a rebuttal to this article. It may be viewed below:
W4XE 1/2007
This site was last updated 01/02/07
