Dan, It's funny that I was thinking about this very issue this weekend while driving to Boston from NYC.
What about having the Squelch control track the background noise level and open the audio above a certain threshold (noise +5-10db?) Would a tracking squelch control provide the desired "quiet" receiver, or are we talking about two different ideas? Craig, KC2LFI ----- Original Message ----- From: "Tayloe Dan-P26412" <[EMAIL PROTECTED]> To: <flexradio@flex-radio.biz> Sent: Sunday, January 21, 2007 3:54 PM Subject: [Flexradio] Noise floor driven, threshold based AGC? > I was listening to a homebrew SDR receiver last night and it stuck me > how noisy it was compared to my analog, narrow band NC2030. As I > thought about this for a bit, I think the reason that the NC2030 is so > quiet (besides close attention of audio chain details), is that it has > no AGC. Thus, I can turn the volume down to where the background noise > is not that high, and tune around the band for signals, and signals tend > to jump out of the (relative) silence and thus tend to stand out against > the background a lot better. > > Given the fact that we have complete flexibility over the AGC in > software, I was wondering if we could do something similar, but better. > > Suppose the receiver does an average noise level calculation over the > sampled bandwidth (min function?) and then set an AGC threshold above > that point (10 db?). If the signal falls into the range of the noise > level up to the new AGC threshold, the signal comes through linearly > amplified. If the signal is higher than the threshold, AGC is applied > to keep it from blasting and or distorting away. > > This might give the best of both worlds where the noise floor is not > needlessly amplified, producing a "quiet" receiver, but where AGC kicks > in when needed to keep large signals under control. This could produce > audio that is much more "listenable" than the current AGC amplified > situation and more controllable than the "AGC OFF" alternative. > > - Dan, N7VE > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > FlexRadio Homepage: http://www.flex-radio.com/ > > FlexRadio Knowledge Base: http://kb.flex-radio.com/ > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com/ FlexRadio Knowledge Base: http://kb.flex-radio.com/
