[ARC5] AVC in SCR-274N receivers

[Kenneth G. Gordon]

On 7 May 2014 at 13:57, Jack Antonio wrote:

> I may have this wrong, or it's not the whole story, but
> I think it is something like this.
> 
> The "AVC" in the SCR-274N receivers wasn't intended
> to be an AVC, that is, it is not supposed to keep audio
> output constant over a wide range of input signals.
> 
> The intent was to keep the receiver from blocking on
> very strong signals.  Or at least to not have the
> audio output decrease as the signal gets very strong.
> 
> The reasoning for this is that in flying the
> old LF radio ranges, (and this is where I am
> on shaky ground), noting
> increasing and decreasing audio levels
> was an important part of the procedure. IIRC
> it had to do with not obscuring the cone of
> silence when directly overhead the range station.

Now that makes perfect sense to me: I have noticed that in order to really see 
what was going on with signal levels in any receiver with a working AGC, one 
really needed a meter on the AGC line: an "S" meter, so-called. 

All subtle changes in audio output were very hard to recognize otherwise.

Ken W7EKB