SCR522

 The SCR522 equipment comprises a transmitter type BC624 and receiver type BC625 carried in a metal case.

See the circuit diagram of the complete installation (in two parts as it's very big)

PART 1 PART 2

It's designed for aircraft use and operates on AM encompassing the aircraft band and covering from 100 to 156 MHz.

The equipment is crystal controlled and is mechanically tuned by an externally mounted relay module which adjusts a set of variable capacitors whose settings were preset prior to a particular mission.

The transmitter has four channels and the receiver two channels.

Recently I was given a transmitter unit which is pictured below.

 

 Front view showing mechanical selectors which control four tuned stages

From the pencilled markings the transmitter might have been in the hands of a radio ham

This type of transmitter was used on the 2 metre amateur band in the days when nearly all VHF transmissions were crystal controlled.

One chose either a 6MHz or 8MHz crystal which when multiplied developed a stable transmission between 144 and 146MHz.

The rear view shows the input circuit to the power amplifier valve, an 832 double tetrode which could generate around 10 watts of power.

 

The third view shows the output circuit

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