The Radar Room

GEE Receiver and the four pluggable RF Units

There were several different part numbers allocated to GEE receivers, although in reality, all were quite similar. Ours happens to be model number R3645. Within all of these units are several IF amplifiers and a video amplifier to drive the CRT on the GEE indicator. Along with this circuitry that is built in permanently, is

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GEE receiver R3645

the completely separate RF unit, which plugs into the front of the main receiver. There were four different matching RF units, the RF24, 25, 26 and 27. These covered four different frequency bands. 22 - 29.7 Mhz for the RF24, 43 - 53.5Mhz for the RF25, 50 - 65MHz for the RF26 and 65 - 80MHz for the RF27. The RF unit in the above image shows RF24 unit which, like the RF25 unit, has five selectable spot frequencies. Both the RF26 and 27 had continuous tuning across the band. All four had a screened RF amp, mixer and a local oscillator.
R3645 with RF27 inserted

The image to the left shows our R3645 during its rebuild on the bench with a restored RF27 unit installed, showing the continuous tuning control. To the right it is interesting to see the state of a similar but rather tatty R1355 unit complete with a rusty front panelled RF26 unit for sale on an auction site. Clearly both are in need of some serious TLC.
R1355 and RF26 in poor condition

As there are no GEE signals transmitted today, the Radar Room is using its own R3645 and RF24 to receive original wartime recordings on an allocated Ofcom low power device frequency, for demonstration purposes.

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