M16A2 Vietnam upper

Special Forces Radio PRC74 Vietnam

The PRC74 radio was used by the US Army Special Forces for long range communications in Viet Nam. It was built by Hughes in about 1965.  It is a ‘lightweight’, two-way communications set that is capable of receiving and transmitting voice (USB) and telegraph signals (CW).    The original frequency range of the radio set for both receive and transmit modes of operation is between 2.0 - 17.999 MHz. It has a stability of +/- 1.5ppm from -30 to +55C.

To find an operating PRC74 these days is pretty rare.

For more details look up "radionerds an/prc-74:.

    This specific radio has a few peculiarities:

    It has no subassembly labels, not even adhesive residue from where the labels would have been.  Perhaps to prevent a captured radio from being identified or repaired. 

   It is a PRC74B but has a PRC74C chassis ID tag. The radio case is desert tan and the battery case is green. It is mounted on an ALICE Backpack frame. The ALICE frame has a 'Kick Stand' and the Battery Case has 'Swing out' support feet.

    It also has a few Modifications:   

     The 2 to 3 MHz range has been switched to 1.8 to 2 MHz so it can operate on the 160 Meters USB or CW. 

     The 17 to 18 MHz range has been switched to 18 to 19 MHz so it can operate on the 17 Meter Band.

         (The original crystals are included to switch it back to the original bands if desired).

    This radio has over 50 crystals in it.  It uses them to mix all the channel frequencies in 1 kHz steps from 2 to 18 MHz.

It has a crystal rubbering feature so it can operate on any in-between frequency, like 14,342.5 kHz.

It is stable enough to run digital modes. I have used it on PSK-31.

      The battery case has an external charging socket and an External/Internal power switch.

If the internal battery gets low you can switch to an external 12V battery.

      The original internal power connector has been replaced with an Anderson Power Pole type and the battery is a 12 Volt LiIon (2P3S, 26650 cells) Battery. There is no battery management controller, (That means you have to turn the radio off or the battery will be damaged). It comes with a commercial (Batteryspace)  LiIon smart battery charger.

    The original final transistors have been replaced with the improved 2N2876's. There are 2 spare RF Power transistors in the kit,

needless to say these transistors are impossible to find.

The entire rig weighs about 30 pounds with the  Li-Ion battery pack.

It comes with one handset, a H-189 or a H-250 handset, Your choice.

The power output is 15 to 20 Watts which you can verify on the Test Set.

   There is also an external audio generator (‘Tuner Upper’)  which allows antenna tuning to be done in a ‘Safe Mode’ at 5W. It also injects a  400Hz offset tone for CW, which puts the responding signal audio at 400 Hz, instead of 2,000 Hz. This accessory has a CW keyer attached. No CW paddle or earphones are included.

 This is not one of those "As is" sales,  This radio was not just found in a barn, It works! I have packed it around and communicated with stations all around the world.

You have to have an FCC license to transmit on this radio.

   The purchase  includes the original AS-1886A segmented center loaded whip antenna with a "Quick On" adapter.

The  1965 price for this radio was $5560, (The cost of a new Chevy was  $2500).

    It comes with the very rare AN/PRM-31B Test Set in new condition. The test set has a Power Meter, Dummy load, a RF Voltmeter, a DC voltmeter and a signal generator to repair the radio in the field. It also has instructions how to trouble shoot and repair the PRC74. It has a set of test cables.

A hard copy of the Technical Manual  TM 11-5820-590-35-1 is included.

   This is a real radio, It has no whiz-bang software or memories that get upset or cause a failure.

Everything is inside is repairable.

  You can read more about the radio by Googling  ‘PRC74’.

PRC90

The PRC-90 radio is a dual-channel, self-powered, personal, emergency-rescue radio that is primarily used for two-way voice or modulated continuous-wave (MCW) communications between a downed crewman and a rescue aircraft. It has a provision for transmitting tone and swept-frequency, homing-beacon signals to guide rescue efforts. It operates on two fixed frequencies and is compatible with all UHF AM radios and UHF direction-finder groups.

The distances for line-of-sight transmission depend on a variety of conditions — weather, terrain, or battery power. At 10,000 feet, voice mode is 60 nautical miles, MCW and beacon is 80 nautical miles, and auto direction finder is 50 nautical miles. On the ground, effectiveness is one-half to one mile or more, depending on terrain.

The newest generation of this radio is the AN/PRC-90-2. It combines the features of the AN/PRC-90-1 into a more useful design that closely resembles the original radio. The typical communication range is similar to the AN/PRC-90-1, but a high-power mode increases the voice range to 125 nautical miles at 10,000 feet. The -2 radio also is rated to operate in water 50 feet deep for five minutes or 2 feet deep for 24 hours.

The AN/PRC-90-2C and AN/PRC-90-T are training radios and operate on a radio frequency that will not interfere with normal search-and-rescue operations.