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" <[email protected]> To: "Elecraft List" <[email protected]> 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: [email protected] > [mailto:[email protected]] 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 > [email protected] > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
