Hi all, There have been some reports (f.i by Rob Sherwood) of AGC's in modern DSP receivers being a bit "restless" (being over-responsive or "dancing on the noisefloor") The K3 AGC is most certainly on the right track but has had some work in the past.
Could the following be the case: Besides prevent clipping in RF/IF stages, in the end of the day our AGC is mainly there to serve our ears. Since the AGC detector stage is triggered by "white" bandnoise, is it not relatively(!) more sensitive to sounds near the high flank of our passband? In other words being triggered relatively more by static and pulse noises, which undermines it's control over the lower voice-content (the vocal-cord part of the spectrum). Up till now I've only seen approaches in the time and gain domain (delaying the attack,modifying the attack/decay timeslopes and onset threshhold) but not in the frequency domain, adjusting some frequencies to have more grip on the agc and some less. In audioland it's quite common to "side-chain" a dynamics processor (compressor/limiter) with a filtered version of the program material you wan't to treat. If you offer the AGC detector an input with a HPF inline it will become less sensitive to bass content. If you offer it an input with a LPF inline it will become less sensitive to high tones. In other words you get "frequency-dependent dynamics processing". If you would use some sort of sloping (pink? ;-) LPF in front of the AGC detector in a DSP receiver, could you prevent it from being overly sensitive to white noise content? It might do a better job on tracking voice and be less responsive to pulse and static type noises near the high slope of the passband. Would this (combined with Rob Sherwoods "delayed attack" transient approach) be an option to really tame the AGC in a near perfect DSP receiver? Excuse me if i'm kicking in open doors... 73' Paul PD0PSB -- View this message in context: http://n2.nabble.com/oh-no%2C-another-crazy-audio-idea-from-Holland-tp2727619p2727619.html Sent from the Elecraft mailing list archive at Nabble.com. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
