[ARC5] SCR-274-N Version "-E" Components

[Kenneth G. Gordon]

On 16 Aug 2016 at 18:32, Mike Everette via ARC5 wrote:

> The early BC-312/342 receivers included slightly 
> different circuitry, a couple of the models having a unique Jones Noise Balancer 
> in the antenna input which was deleted in later production; either not that 
> effective in practice or too tricky to use.

Too difficult to use, from what I have read. 

Also, it was most useful when the BC-312/342 was used in a mobile installation, i.e., in a 
jeep. The "noise antenna" was a probe installed inside the engine compartment.

That noise-cancelling system would have had minimal effectiveness when used in a fixed 
station environment. It had no effective way to balance the gains of the two "antennas".

Modern noise-cancelling systems such as the MFJ-1276 and others like it work on the same 
principles, though.

There was a long and most excellent article on noise-cancelling systems by Mike Murphy 
WU2D in an Electric Radio Magazine some time ago in which the BC-312/342 system was 
discussed.

Ken W7EKB