CQWW CW from P49Y in 2009. Because I wanted help thinning out the pileup,
detect weak signals while still having protection against very strong ones.
> On Dec 9, 2010, at 12/9 9:17 AM,
[hidden email] 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
>
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