

This picture shows typical communication receivers in use in the late 1950’s
The technology at this point is still 100 percent valve.
Manually operated, they employed a tuned front end, VFO or Crystal controlled local oscillator and had a relatively low first IF – around 3 MHz.
Automatic frequency control was achieved using a frequency discriminator which drove a small tuning motor to lock on to the pilot carrier of a ISB transmission. AFC also employed on telegraphy receivers.
Dual front ends were included for diversity reception with automatic selection of the best signal path.
The GFR was nice to operate – good AFC (Story about Salisbury)
The HR 11 was a telegraphy version with dual diversity.