The AN/PRC-77 Portable Transceiver, also known as AN/PRC 77 Radio Set, is a man-pack, portable VHF FM combat-net radio transceiver manufactured by Associated Industries[1] and used to provide short-range, two-way radiotelephone voice communication.[2] In the Joint Electronics Type Designation System (JETDS), AN/PRC translates to "Army/Navy, Portable, Radio, Communication."
The AN/PRC-77 entered service in 1968 during the Vietnam War as an upgrade to the earlier AN/PRC-25. It differs from its predecessor mainly in that the PRC-77's final power amplifier stage is made with a transistor, eliminating the only vacuum tube in the PRC-25, as well as the DC-DC voltage converter used to create the high plate voltage for the tube from the 15 V battery. In addition, the PRC-25 could not support voice encryption devices, but PRC-77 transmitter audio bandwidth was widened to give it the ability to use the TSEC/KY-38 NESTOR voice encryption system used in Vietnam, and the later KY-57 VINSON family. Problems were encountered in Vietnam with the combination as described in the NESTOR article. The transmitter's spurious emissions were cleaned up to create less interference to nearby receivers. The receiver's performance was also hardened in the PRC-77 to enable it to better reject interference suffered from nearby transmitters, a common operating set up that reduced the effectiveness of the PRC-25.[3] The receiver audio bandwidth was also increased to operate with the encryption equipment.[4]
There were no changes to the external controls or looks, so the two radios looked and the operating controls were the same. The equipment tag glued to the edge of the front panel was the main (external) way to tell the difference. The original batteries had a 3 V tap (series diode-reduced to 2.4 V) for the PRC-25's tube filament. This remained unchanged so the batteries could operate either radio it was placed in, but the PRC-77 did not use the 3 V tap at all. With the more efficient all-transistorized circuitry, and without the DC-DC step-up voltage converter for the tube, the common battery lasted longer in the PRC-77 under the same conditions. "OF THE TWENTY-FIVE (25) ELECTRONIC MODULES ORIGINALLY USED IN BOTH THE TRANSMITTER AND RECEIVER PORTIONS OF THE AN/PRC-25, ONLY EIGHT (8) OF THE MODULES USED IN THE AN/PRC-77 ARE INTERCHANGEABLE WITH THE AN/PRC-25.'"[5]
Today the AN/PRC-77 has largely been replaced by SINCGARS radios, but it is still capable of inter-operating with most VHF FM radios used by U.S. and allied ground forces.[6] It was commonly nicknamed the "prick-77" by U.S. military forces.[7]
The AN/PRC 77 consists of the RT-841 transceiver and minor components. It can provide secure voice (X-mode) transmission with the TSEC/KY-57 VINSON voice encryption device, but is not compatible with the SINCGARS frequency hopping mode.[6] During the Vietnam War, the PRC-77 used the earlier TSEC/KY-38 NESTOR voice encryption system.
Major components:
Minor components - CES (Complete Equipment Schedule):
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