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Old May 29th 05, 08:23 AM
Ian Jackson
 
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In message , Tom Holden
writes
Thanks to all for the constructive and informative discussion.

I believe 'delayed AGC' means a slower or delayed attack at the RF stages;
in the DX-394, there is a R-C network adding maybe 15 ms to the attack on
the AGC line affecting both the 1st mixer and the drain-source current of
the RF preamp and a second network adding maybe 10 ms on top of this
affecting the AGC gate of the RF preamp. I've doubled that first time
constant and doubled what I would like in my attack and release networks in
order to get the fastest stable speeds which I guess would be on the order
of 20-40 ms attack and 50-80 ms release.


73, Tom



Tom,
I haven't been following this thread. However, in my understanding,
'Delayed AGC' doesn't refer to a time delay. It normally means that the
AGC in the RF stage doesn't cut in until a certain level of signal is
reached. AGC is applied as 'normal' to the IF stages but the RF stage is
held at maximum gain until the input signal is higher. The effect is to
obtain a better signal-to-noise ratio with low-level signals.
Ian.
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