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AN/PRC-25 and AN/PRC-77 Backpack Radio
Radio Set AN/PRC-25 was the state-of the-art FM tactical radio for the Vietnam War. The mostly solid-state design brought weight down to less than 20 pounds with battery vs. 26 pounds for the AN/PRC-10.
AN/PRC-25 Backpack Radio History
Prototypes of the AN/PRC-25 were initially tested in 1959 and it was ready for issue to Army units during 1962. In July 1965, responding to General Westmoreland's complaints about the AN/PRC-10, the new, transistorized FM radios of the AN/VRC-12 and AN/PRC-25 families were diverted from Europe and were shipped to Vietnam.
The first AN/PRC-25's in Southeast Asia (mid-1965) were intended for advisers. With their initial distribution came the first NET Team (new equipment training) from the Electronics Command to begin instruction on the operation and maintenance of the VRC-12 and the PRC-25. Those radios soon became the mainstay of tactical communications in Southeast Asia. In three and a half years, 20,000 VRC-12 and 33,000 PRC-25 radios were delivered to Southeast Asia. The PRC-25 was, according to General Creighton Abrams, "the single most important tactical item in Vietnam."
The PRC-25 was the radio that made military tactical communication reliable and the basis of tactical command. The PRC-25 and it's immediate successor (the PRC-77) were widely used across the globe for almost 30 years with about 130,000 sets produced in total. Over 40 countries adopted the radios and the design of the radio and spares was licensed to numerous manufactures in the US and among allied nations. It remains in widespread use today even after it has been superceded by more up to date equipment.
Individual manufacturers have upgraded the design in order to offer models similar to, but not identical with, the AN/PRC-77 as issued to US forces (for example adding more channels by using 25 kHz spacing instead of the 50 kHz spacing of the PRC-77). These often have model numbers that are not officially used, like PRC-177.
Either radio was signal compatible with the other and also with VRC-12 and with the AN/ARC-54 aircraft radio set and with the PRT-4 and PRR-9 squad radio. The PRC-25 was organic to battalion-size units and was issued through platoon level.
The PRC-25 design had many firsts, all intended to make it much easier to carry and use than previous models such as the AN/PRC-10. It was the first solid state FM backpack radio but also incorporated new ideas for radio circuits (such as "150 Hz squelch feature") that made it easier for the average soldier to use by reducing controls to a minimum.
Radio Set AN/PRC-25 had 920 channels spaced 50 kHz apart, operating in the 30-75.95 MHz spectrum. It transmitted about 1.5 watts of power. Operating distance was typically three to seven miles with the standard antenna. The radio could be carried with a web suspender rig or mounted on the LC-2 pack frame from the ALICE pack equipment.
AN/PRC-77 is the upgraded version of the AN/PRC-25
The AN/PRC-77 set was an improved version of the PRC-25. Specifications and accessories for the two radios are nearly identical. The only important differences in design were internal; they are virtually impossible to tell apart externally. The AN/PRC-77 includes a solid stare power amplifier that does away with the PRC-25 2DF4 power amplifier tube in the final transmitter section. Its completely solid state design made it more reliable and reduced its power requirements. Filters were added to reduce interference. The PRC-77 also includes the capability to work with X-mode speech encryption to respond to the need for greater communications security. The PRC-77 radios could be used for secure voice communications with the addition of NSA designed COMSEC boxes (KY-38 and later KY-57).
The AN/PRC-119A is the manpack version of the SINCGARS radio and is the replacement for the PRC-77 with US forces.
AN/PRC-25 and AN/PRC-77 in Other Configurations
There were three basic configurations of the PRC-25: starndard manpack, vehicular (called AN/VRC-53 in that configuration), and dual manpack or vehicular (AN/GRC-125 configuration). The PRC-77 also had these combinations available, but with different nomenclature as explained in the following.
AN/VRC-53 Radio System refers to RT-841/PRC-25 when installed in the AM-2060 Audio Amplifier/Power Supply and connected to the AS-1729/VRC Vehicular Whip Antenna. The MT-1029 Vehicle Mount is used to install the AM-2060 in a vehicle. The MT-1029 also supports use of the VIC-1 Vehicle Inter-Communication system.
AN/VRC-125 dual purpose system (vehicular or manpack) includes the vehicle set up as above, plus the ST-138 web suspenders back pack, battery set and the CW-503 accessories bag.
The AN/PRC-77 is the basic receiver-transmitter equipment used in the vehicular sets AN/VRC-64, AN/VRC-65 and AN/GRC-160.
The AN/VRC-64 is the vehicular version of the RT-841/PRC-77 portable Radio Set, consisting of: Receiver-Transmitter mounted on the Amplifier-Power Supply Group OA-3633/GRC. It also includes the AS-1729/VRC Vehicular Whip Antenna.
The AN/GRC-160 consists of an AN/PRC-77 Radio Set, including all the vehicular components covered above and as noted in the AN/VRC-64 as well as all standard Manpack accessory items. The AN/PRC-77 can be removed from the vehicle and used as a battery-operated Manpack Unit and later returned and mounted back onto the OA-3633/GRC resuming vehicular operation.
Accessories for the AN/PRC-25 and AN/PRC-77
The accessories in the following list are commonly used with the AN/PRC-25 and AN/PRC-77 backpack radios. In addition to the standard issue antennas, operating distance for the AN/PRC-25 or PRC-77 could be extended to as much as 20 miles by using the RC-292 ground-plane antenna with its thirty foot mast.
Technical Manual for the AN/PRC-77
The technical manuals for the AN/PRC-25 were TM 11-5820-398-12, Operator's & Organizational Maintenance Manual Including Repair Parts List, Radio Set AN/PRC-25 and TM 11-5820-398-35 Field & Depot Maintenance Manual.
As of January 1987 the technical manual for the AN/PRC-77 was TM 11-5820-667-12, Operator's & Organizational Maintenance Manual, Radio Set AN/PRC-77 (NSN 5820-00-930-3724). This edition includes changes to earlier editions of the TM.
Find More Information on the Internet
There are many fine websites that have additional information on this topic, too many to list here and too many to keep up with as they come and go. Use this Google web search form to get an up to date report of what's out there.
For good results, try entering this: radio prc-25 or prc-77. Then click the Search button.
The web site "PRC-25, Forgotten Legend" by Dennis Starks has a very comprehensive history of the PRC-25 and its sister PRC-77 radio sets.