The Corsair AGC is created at audio and I think after the notch and
bandpass filters. Those plus the many poles of cascaded crystal filter
add up to a great amount of delay. So by the time the AGC voltage has
come up (on the slope of an 700 Hz sinewave, not a 9 MHz sinewave if
done at IF) there's been a lot of signal passed to the cascaded filters,
IF and audio, that the AGC can't control. Simply because the big signal
has passed the gain controlled stages. The thump can be reduced by
speeding the AGC attack, probably at the cost of poorer gain control.
Nearly always, backing off on the RF gain control to reduce that strong
signal's level calms the thump. Running slow AGC kills off the thump
except on the first CW character element.
Probably the Omni D has fewer poles of cascaded filters, so the AGC has
a better chance of working fast.
73, Jerry, K0CQ
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Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.
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