RAF-part 10D/1307

What is this, I found it in a B21B receiver (Admiralty) but it is a AirMinistry part ???????

A calibrator with a 100 kHz crystal.

X-tal is dated December 1944.


It belongs to receiver Type 78 ( RAF-part 10D/1307)

This is the Type 78 receiver.

Top-view of the calibrator.

Looking at the right side of the receiver.

The radio is part of the ARI-5206. ARI means Aircraft Radio Installation and the 5206 system, first released around 1943, was installed on different aircraft types.

The complete equipment group listed for the ARI 5206 at the Kurrajong Radio Museum is as follows:
HF receiver Type 78      (2.4 - 13.0 MHz)
HF transmitter Type 53  (2.4 - 13.0 MHz)
MF receiver  Type 76
MF transmitter Type 51
Modulator unit Type 76
Aerial tuning unit Type 126
Type 260 control unit for any Air Gunners
Type 276 control unit for any Observers
If all the equipment above was used together, it was known as "Four Square". If only  the 78 receiver and 53 transmitter were fitted, it was called "Two in Line". It is now believed that the Two-in-Line system was the one installed in the Firefly.

Two in line

Thanks to Jan de Vries.