K3 Notch

[W0EWM]

The problem with having the manual notch filter outside the AGC
loop is that if you are trying to notch out a CW signal, although the tone is
eliminated, the notched signal causes the AGC to pump - thus hurting weak signal
copy. I think whenever you start using the"big tools" you have an idea that you
are not in the  "optimum receive situation." For me, the ideal would be "auto
notch" outside the  loop and "manual notch" inside the loop.
73, Merle - W0EWM
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On 4/26/2010 7:30 PM, N1JM wrote:
>
> It's a shame. Such a sophisticated high end radio and no notch within the agc
> loop.

Part of the problem is that a DSP radio needs to have the notch after
the AGC since part of the function of AGC is preventing the ADC from
being over driven.  If the notch is placed BEFORE the AGC detector
the notch will cause the interfering signal to INCREASE at the input
of the ADC.

Yes, it would be nice for the notch to allow the receiver to return
to normal gain when the interfering signal is removed but that would
merely cause the HAGC to come into play.

73,

    ... Joe, W4TV
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[ab2tc]

Why is this not a problem if the regular brick wall filter removes a carrier outside of its passband but inside the roofing filter's passband? I understand that if the carrier is strong enough, the HAGC will eventually kick in, but the DSP main filter is certainly capable of removing significant interference without ill effects and it's inside the AGC loop.

AB2TC - Knut

W0EWM wrote

The problem with having the manual notch filter outside the AGC
loop is that if you are trying to notch out a CW signal, although the tone is
eliminated, the notched signal causes the AGC to pump - thus hurting weak signal
copy. I think whenever you start using the"big tools" you have an idea that you
are not in the  "optimum receive situation." For me, the ideal would be "auto
notch" outside the  loop and "manual notch" inside the loop.
73, Merle - W0EWM
<snip>