On Dec 9, 2010, at 12/9 9:17 AM, k...@aol.com wrote: > But, since AGC works on every signal in the passband, if there are > two signals - one S9 and the other S3 appearing at the same time, > the S3 signal will disappear because the AGC is knocking down the > S9 signal to an S3 level and thereby also reducing the S3 signal to > the noise.
My impression from reading what has transpired is that some people are more concerned that when the S9 signal is *not* there, that the S3 appears to be too loud? We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. Perhaps people will be happier if the AGC response is not as linear (in the log-log scale) as the one in the K3 once you have past the AGC threshold. I.e., perhaps people would care less if an S7 signal sound as loud as an S9 signal, but they do want the S3 signal to sound less loud as the S7 signal. A non-linear transfer function like that is certainly "easy" to implement (as long as I don't have to be the one to implement it :-), but will this make more people happy? Who knows? Basically, this is what I am simple-mindedly visualizing: currently, there are only two parameters to control a piecewise linear curve. Imagine that there are three parameters, the current two, plus a "upper threshold," after which the slope becomes "15" (i.e. flat at S0 to THR, then constant "SLOPE" until "upper threshold" and then flat from there until the front end starts to smoke),. You then smooth out the piecewise linear curve using a pair of homotopy between those three partitions. You will end up with (1) a smooth curve instead of the piecewise linear one currently, and (2) a way to say "I care more about distinguishing an S3 from an S9 signal than I do an S7 and S9 signal." Notice that if a simple homotopy is applied to smooth the AGC transfer function, and even if "upper threshold" is set to S7, you will still hear a difference between S7 and S9 -- just much less than between S3 and S9. Also, if the AGC curve is no longer piecewise linear you will still hear the S3 signal even if the lower threshold is set to an S3. I still think the only way to satisfy "everybody" is if everyone would homebrew their own rig, or sell an "open" commercial rig where you are allowed to make any mods -- hardware, firmware, or software. See first option :-) :-). 73 Chen, W7AY ______________________________________________________________ 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
