Wireless Set No. 52 Canadian - Project

[Chris Suslowicz]

Originally Posted by Bruce MacMillan

The Canadian Marconi CSR5 receiver also uses this device. It's purpose is to protect the receiver front end from damage by HV static. The one used in that receiver is described as:
antenna discharge gap Admiralty Pattern Type 8431 C.G.E.

It breaks down at 100V. It has no effect on the operation of the set. I suspect that as both sets were made by Marconi it could be the same part number.

I would guess that unlike a fuse it is a reusable part.

Having noticed it on the circuit diagram while rummaging for the connector details further up the thread, it appears on the circuit diagram as "Spark Gap" and is noted in FZ522:

RECEIVER

R.F. Amplifier V1A (ARP3)

30. The input to the tuned R.F. amplifier is
taken from the P.A. tank circuit in the
sender. When the sender tank circuit is
tuned to the receiver frequency its resonant
characteristics contribute to the image
frequency attennuation and slightly to the
sensitivity. A gas-filled discharge gap,
SG1, is connected across the input terminals.

Under "Miscellaneous" in the receiver parts list it's described as:

"SG1 100W. neon discharge gap".

(I assume the 100W is a typo for 100V.)

Chris.