[Elecraft] K3 receiver desensing on CW during contest

[Erik N Basilier]

There are two separate AGC functions:

1. Hardware AGC is activated when the combined signals that get through the 
roofing filter reach a certain level, about S9+25.
When it is activated, all those signals, including the wanted signal, are 
attenuated before the DSP.
AFAIK the hardware AGC cannot be turned off.

2. Software AGC implemented within the DSP. It can be turned on or off, and 
its parameters can be adjusted. I am not sure whether it is ever totally 
turned off, even when "turned off". It reacts to the strenght of all that 
has passed through the DSP bandwidth.

Signals outside the DSP passband but inside the roofing filter certainly 
enter the DSP, but the DSP bandpass filter should eliminate them before they 
can do anything to the software AGC. They can affect the hardware AGC, but 
only if they together (including the wanted signal) are so strong that the 
hardware AGC does anything at all.

Erik K7TV

----- Original Message ----- 
From: "Darwin, Keith" <Keith.Darwin at goodrich.com>
To: "Elecraft List" <elecraft at mailman.qth.net>
Sent: Monday, February 23, 2009 12:22 PM
Subject: Re: [Elecraft] K3 receiver desensing on CW during contest


> I'm at work and don't have time to check any of this ... But I was under
> the impression that it was not this way.  Signals outside of the DSP
> passband but inside the roofing filter passband would activate the DSP.
> So, with a 2 KHz roofing filter and a 200 Hz DSP, you'd have very few
> signals being heard by the OP but lots of signals affecting the AGC.
>
> - Keith N1AS -
> - K3 711 -
>
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Steve Ellington
> Sent: Monday, February 23, 2009 1:58 PM
> To: Jim Brown; Elecraft List
> Subject: Re: [Elecraft] K3 receiver desensing on CW during contest
>
> Is this correct?
> If a cw signal falls within the DSP passband it should and will pump the
> AGC. If a CW signal falls outside the DSP passband it should not pump
> the DSP's AGC. Steve Ellington
> N4LQ at carolina.rr.com
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