The APF feature of the K3.

Posted by Geoffrey Mackenzie-Kennedy on Feb 03, 2011; 8:03pm
URL: http://elecraft.85.s1.nabble.com/The-APF-feature-of-the-K3-tp5990251.html

Hi Vic,

Do you know if any plot of the frequency response K3's APF exists, or any
similar data about its bandwidth at different levels of attenuation, and is
its response "peaky"?

I might have told you that as part of the ongoing development of my MkII
H-Mode receiver, I have for some time been considering various additions to
its audio circuitry - one of which is some form of APF.  The use of DSP is
not an option for this receiver, because any ADC that I can afford would
most likely ruin the 110db+  in-passband dynamic range of this receiver. Nor
is any form of Q-Multiplier

It has struck me though that an Audio Bandpass filter, whose bandwidth at
the 1db points is say a few Hz without a "peaky" response, might possibly be
a useful device to use as an APF rather than a filter whose response is
"peaky" -  when digging out signals in the noise floor. This is speculation
because I have not yet had the time to build and evaluate the performance of
an AF bandpass filter for this application.

73,

Geoff
GM4ESD

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