Military Rescue Radios in the Age of the Transistor, New Battery Technologies, and Antenna Choices.

Note: Rescue radios in particular are generally considered to be un-repairable since hermeticity after repair might be hard to prove, and a repairable unit would tend to be physically larger and heavier than one not designed to be disassembled and reassembled.

1)-In the era surrounding WW2, battery technology offered just two types, Flashlight cells and Mercury cells. The former lasted from one week to a month (if stored in a refrigerator), while mercury cells lasted quite a while longer (at the expense of cost, weight, and environmental issues).

2)-Although transistor technology came along, it was quite a while until suitable semiconductors became available that could be used at the RF power levels required (~0.5 to 2 Watts) at VHF frequencies (30-300 MHz).

3)-Some of the initial radios built employed plastic housings and/or used telescoping antennas (therefore rigid), neither of which were appropriate for the (rough) environment in which they were to be used.

4)-This brought the Navy to contract GTE/Sylvania in Needham, Massachusetts to develop a rugged metal cased single channel radio nomenclatured AN/PRC-63. GTE also developed a 12V mercury battery, BA-1568U for this radio. The antenna was what we call today a “rubber ducky.” GTE sized the antenna length to be 12”, i.e. a quarter wave at the 243 MHz operating frequency. Quarter wave antennas are generally considered to offer the lowest reactance to the antenna drive circuitry, leading to a simpler interface. This does not mean, however, that they offer the best “gain”, that is the strongest signal at the horizon, or perhaps slightly higher in elevation for searching aircraft. ACR and perhaps others did offer longer antenna versions on their rescue sets.

5a)- PRC-90, PRC-90-1, PRC-90-2

NASA needed a two channel radio, and given the success of the PRC-63, GTE received the development order for what became the AN/PRC-90. GTE used the same battery and antenna from the PRC-63, and successfully developed this set. (NOTE: There is some historical evidence (a picture) that may indicate that the NASA unit was in reality a step between the PRC-63 and the PRC-90.) GTE’s initial design used hybrid construction techniques, and a quarter wave antenna. Alternate sources also used the hybrid construction technique, but switched to a base loaded antenna of 22”. After some production, internal circuitry improvements were made using standard electronic components (design was done by ???), and while using up the stock cases, was nomenclatured AN/PRC-90-1. With a new case (with a better microphone), the nomenclature changed to AN/PRC-90-2. In addition, the antenna loading components for both the -1 and -2 were incorporated inside the case, saving money on the cost of the antenna. Antenna length measured 21”.

- Other radios based on the PRC-90

• PRC-106, 121.5/243 MHz version

• PRC-103, Air Force pararescue set

• PRC-125, Navy pararescue set

6)-Batteries, Batteries, Batteries

• Eventually, the mercury battery was outlawed because of environmental concerns. BA-5368U lithium version is NLA also. A sleeve battery holder (4 ea. CR123 Lithium batteries @ 3V ea, 12V total) was developed to extend the life of the AN/PRC-90 radio.

• Lithium batteries are not allowed on submarines. The Navy turned to GTE to develop a 6 Volt 2 frequency (121.5/243 MHz) radio version (power supplied by either B9569 Li/SO2 single 6 Volt battery (not for submarine use), or by 4 ea 1.5 Volt “D” alkaline cells housed in a special sleeve battery holder extension). (4 ea. Alkaline “D” cells in series makes the required 6 Volts). This was nomenclatured AN/PRC-96, and was produced by C-RAN Corp. and GTE-Sylvania. Please notice: 10 year shelf life on some modern Alkaline batteries. Antenna is special, and is 8” long.

7)-Next came the ever more complicated AN/PRC-112, used ones of which are on eBay for between $165 and~$1500 depending on version. Antenna is a 14” long tape.

a)- The PRC-112A through C (I think) offered 7

frequencies, as follows.

1)-243 MHz

2)-243 MHz Beacon

3)-A (choose your own), ***

4)-B (choose your own), ***

5)-282.8 MHz

6)-121.5 MHz

7)-121.5 Beacon

*** Frequency must be within one of the following ranges---

-118-125 MHz

-225-320 MHZ

-340-390 MHz

-406 SARSAT if model is so equipped

There is a foreign source selling the simpler versions for $165 Ea.

b)-The PRC-112D and higher have a slightly different appearance and offer additional features, like in some cases GPS (i.e. HOOK-112) and can command an asking price of $1500 ea. and up.

8)-Next came CSEL (Combat Survivor/Evader Locator), a Boeing program (AN/PRQ-7). The object is to locate downed airmen within 15 minutes or so. The Navy decided, because of the high cost of this program, that it would implement it only for rescue kits aimed for combat areas. Non-combat areas received a Tadiran portable nomenclatured AN/PRC-149.

9)-PRC-434A now on the surplus market has a 16” long tape antenna.

Alan Tasker WA1NYR