Re: Attenuator and RF Gain Settings

Posted by Jim Brown-10 on Feb 02, 2010; 11:15pm
URL: http://elecraft.85.s1.nabble.com/Attenuator-and-RF-Gain-Settings-tp4503505p4504396.html

On Tue, 02 Feb 2010 16:34:50 -0500, Don Wilhelm wrote:

>BUT one *can* make that happen with incorrect settings.

YES! Don has given us a LOT of great advice in his two recent
posts in this thread. Let me emphasize something that I'm sure he
understands, but didn't make quite it clear if you didn't read
between his lines.

NOISE IS PART OF THE SIGNAL THAT IS DRIVING THE AGC. IT IS ALSO
PART OF THE SIGNAL THAT IS GENERATING INTERMOD, BOTH AT RF AND AT
AUDIO. IT IS PART OF WHAT THE IF SELECTIVITY MUST REJECT, JUST
LIKE ANOTHER STATION!  

CAPS ADDED FOR EMPHASIS.

If the NOISE overloads the signal chain, the resulting distortion
obscures the signal. It is not enough to keep the signal chain
below overload on signal. We must also keep it out of overload by
noise pulses. That's not easy, because much of the noise at the
antenna terminal is impulsive in nature -- certainly static and
stuff like fences.

Bear this in mind when setting ATT, PRE, RF gain, and AGC
parameters.

73,

Jim K9YC


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