[Elecraft] Hearing the effect of narrower roofing filter

[K7TV]

When the hardware AGC responds under these conditions, I am guessing that the
effect might be an increase in the general background noise heard. This is
really what I was after. 






After looking at the clock last night and finishing off my post too quickly,
I got poster's remorse about the last sentence. Of course, if the hardware
agc works perfectly, I would expect the general effect to be a decrease in
noise. Behind my sentence were two muddled thoughts: 1. If the agc hang or
decay is very short, the random peaks in composite signal might cause very
rapid sequences of normal/desensed noise, and this staccato effect might be
perceived as an addition in noise although not increasing noise amplitude,
and 2. This being a new radio design, it would not be inconceivable if some
aspect of the agc design were flawed, resulting in actual increases in noise
amplitude when the hardware agc kicks in repeatedly at a high rate.

I received one response, off-list, that was aimed at this part of my post.
The gentleman provided a great deal of insight into what might go wrong with
the agc action and the second mixer. Those details went far beyond my
thoughts. Unfortunately he did not actually have a K3, so there was no test
data.

I guess I had better be patient and wait until my K3 arrives! It should be
easy to study the hardware agc action by using an external preamp to bring
up the average signal level on a crowded band. I might hang one scope
channel on the 8 MHz signal after the filter, and another channel on the
hardware agc voltage, while listening to the radio. Of course, since noone
on the list is obsessing about this aspect of K3 behavior, it will probably
turn out to be unimportant to the overall performance of the radio.




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