PRC-41 UHF

Portable communication

VINTAGE AVIONICS

RT-695/ PRC-41

Portable UHF Transceiver based on the ARC51

1964

Photo: On the front of the R/T unit are two plugs for two handsets. In the RT695A version one of them connects to the KY-38 secure voice unit.

Either the silver-zinc battery (BB-451/U) , or the ac power supply (PP 3700) is attached to the bottom of the RT695 /PRC-41 transceiver.

The PRC-41 is a portable transceiver for ground-to-air service, built with modified modules from the ARC-51. It is intended for forward air control.

The radio has 1750 channels in the military 225-400 MHz band, spaced 100kHz. Output power is approx. 2W ( 3W max). The unit is supplied by 26Vdc, at 2A in receive, or 2.8A in transmit plus a short (7ms/ 2A ) pulse when changing the T/R switch from Rx to Tx or back.

The PRC-41 was followed up in 1969 by the PRC-66

Components:

Transceiver RT 695 / PRC-41 28 x 10.5 x 35 cm , 10.5 kg

Power Supply PP-3700 28 x 10.5 x 19 cm , 7.5 kg

Battery BB-451/U 28 x 10.5 x 19 cm , 7.5 kg

Mount MT 2976 ( vehicle mount, connects to car battery)

Antenna AS 1404 ( omni directional)

AS 1405 ( directional log-periodic)

Circuit diagrams and some data are here.

Transceiver Like the ARC51, The RT695 is a triple superhet with fully crystal controlled channels. Differences to the ARC51 are: Manual control, no crystal oven, simplified squelch circuits and only 2W RF output.

Versions: The RT695A has a slightly modified audio circuit to allow secure voice communication using the external crypto unit KY-38

Battery The battery has 16 silver/ zinc oxide cells, filled with potassium hydroxide (KOH). The nominal voltage and capacity is 24V, 25Ah, although it was recommended not to discharge beyond 20Ah.

With a cycle of 1 minute transmit and 9 minutes receive, the battery will last 12 hours at an ambient temperature between –20 and +35 deg. C.

The battery can be recharged up to 20 times with 16 x 2.03 = 32.5V, initially current limited to 2.5A. After 20 recharge cycles, the battery is discarded, and the silver is recycled if possible.

AC Power Supply The PP-3700 is a transformer-ballast type power supply with 26.5V output at maximal 4.5A, in exactly the same case as the battery.

The PP-3700 is not physical nor electrical suitable to recharge the battery.

FM Comm

VHF Communication