Transmitter ST23 and Receiver SR23

The transmitter type ST23 and receiver type SR23 are a matching pair of VHF equipment types designed and manufactured in the UK by STC (Standard Telephones and Cables Ltd). They were used in a number of aircraft during the late 1950’s and early 1960’s including the Comet, Vanguard, Viscount, Convair 210 & Argosy.

They are typical of a new generation of airborne (and navigation) VHF communications equipment designed in the 1950’s. Instead of a complete transmitter and complete receiver having to be located in the aircraft cockpit, it became possible to “remotely control” the main equipment with just a Control Unit in the cockpit and allowing the main equipment to be located elsewhere in the aircraft.

These are among the first generation of equipment to use modern miniaturisation techniques including transistors and PCBs (printed circuit boards).

Transmitter data
The frequency band covered is 118 – 135.95MHz giving a total of 360 channels at 50kHz spacing.

The RF (radio frequency) output is 20W.

Receiver data
The frequency band covered is 118 – 135.95MHz giving a total of 360 channels at 50kHz spacing.

All spurious responses are at least 90db down (a major advance on previous designs and still typical of 21st century equipment).

General
A Control Unit is available to cover either the whole band of 360 channels or only the communications band.

Power supply requirements are 115V 400Hz single phase AC or 28V DC.