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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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