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Development of PRC-90; by Alan Tasker, WA1NYR

In the mid 1960's, the services fighting in Vietnam needed a two frequency rescue radio in a hurry. Many planes were being shot down, and they needed a second channel other than 243 MHz. GTE Sylvania in Needham, MA was producing the PRC-63 single channel rescue set, and won one of the contracts to design and make a set for the Navy. It carried the designation AN/PRC-90, and had a second frequency of 282.8 MHz.

Other radios were also developed in this time frame, such as the ACR produced RT-60, also on these two frequencies, and the Magnavox produced 4 channel radios AN/PRC-64 (Air Force) and AN/PRC-68 (Army).

GTE used modular construction, i.e. soldered components on ceramic plates, and potted to keep moisture out. Everything was hard wired, and basically, non repairable.

Sometime in the mid 80's,
the radio was still going strong. However, it was decided to improve things by a
redesign using Integrated Circuits that were developed in the last 20 years, as
an AM radio chip and audio chips to drive the speaker and the modulator. It was decided to make everything plug in so that repair would be easy.
PC board construction was used because it was much less expensive. A new case was planned that would improve audio
(electret microphone in place of the former dynamic mic element on the first case). Meanwhile, the new circuitry had an audio interface for either the old or new microphone.
Morse code use was removed, and in its place was a
button for a higher power beacon. Lastly, again for economy sake,
the loading coil for the half wave antenna was added inside the radio case.

There were then
three types of antennas used over the life of the program.

First was a short, quarter wave antenna that did not work very well, and was soon replaced by the design below.
Then came the half wave antenna with the bottom section being a sheathed spring, and the top being a telescoping design. There was a larger diameter base that contained the matching section. This design was used on most PRC-90 radios built.
Lastly came a half wave constructed design as above except without the bulgy base containing the matching section, because the PRC-90-1 and PRC-90-2 had the matching section inside the radio.

When an older style PRC-90 case was built with the new electronics, a decal reading "HI PWR BCN" was placed over the case engraved words "MCW" (MCW being blacked out). This style unit was nomenclatured an AN/PRC-90-1.

Eventually, all the old style cases were used up, and the new style became the norm. These units were nomenclatured AN/PRC-90-2. (MCW being no more on the frequency plate)