[Elecraft] More AGC

[Ron D'Eau Claire]

> In my experience, the audio of most receivers , the K-2 included, is
> improved by turning off the AGC when receiving moderate to strong CW
> signals. The fixed signal to noise ratio that AGC imparts under these
> conditions is unpleasant to me. Also, on moderate to strong signals when
the
> AGC is turned off, I can reduce the RF gainto get rid of  most of the
noise
> and increase the AF gain to bring up the signal for nearly noise free
> reception. This only works well when the audio stages are low noise of
> course.
> James R. Duffey KK6MC/5

 I have a home brew single-conversion superhet receiver that I designed
along the guidelines suggested by Wes Hayward in "Solid State Design for the
Radio Amateur".  The audio amplifier is a very low noise class "A" circuit
for just the reasons you describe. I can turn up the audio gain and hear
silence until I advance the r-f gain. With careful attention to low noise
circuits, the receiver has much of the "clarity" and "transparency" of
hearing that devotees of  high-performance "direct conversion" receivers
rave about.

 I built it in the 1970's, and to this day it has a non-functional S-meter
on the panel. I added the S-meter because I wanted to spend some time
experimenting with high-performance AGC circuits and thought that a meter
might come in handy for using the receiver as a precise signal level
measuring device. The S-meter is non-functional because I never found an AGC
circuit
that I was satisfied with. I sure did build a lot of them, though <G>.

The receiver does have a very good hard audio limiter that kicks in before
my ears (or the phones) blow out should I hit a very strong signal (or get a
big noise pulse) with the gains up. The limiter creates a lot of distortion
when it clips signals, of course, making them sound fuzzy. But the limiter
is only a protective circuit that operates until I turn down the gain
control.

I wonder if what is happening today is that so many ops have used AGC on
their receivers from the first time they listened to the short-wave bands
that they have gotten used to the idea of all that noise rising up between
signals as "normal". If so, then of course not using AGC  and hearing weaker
noise and signals between the stronger ones would sound as unnatural to them
as hearing all that racket between signals does to the rest of us.

To me it's not a case of "right" or "wrong" any more than straight keys vs.
keyers are "right" or "wrong", but rather which technology we have grown
accustomed to using.

I'm glad the Elecraft guys included an "AGC OFF" function. Thanks!

Ron AC7AC
K2 # 1289