Topband: Receivers, Noise Blankers and Key Clicks

[Tom Rauch]

Very interesting Jim. That's another good case the ARRL publishing
close-spaced testing.

> Depending on what signals are present within the 15KHz wide
> roofing filter, what you hear can be anything from keyclicks
> to 'thumps and bumps' from lowpass filtered keyclicks, to
> a 'growling' sound on ssb...to the am detected envelope of
> your signal of interest, injected after the product detector
> audio.  Essentially, you're interfering with youself.

The symptoms sound like what the FT1000's (and other Yaesu rigs) do except
in them it is caused by IM products in a FET amplifier left hanging off the
IF system.

If close-spaced dynamic tests were published in QST reviews, many of these
problems would be corrected. Manufacturers will only test the parameters
that get headlines in reviews, so the real key is getting the ARRL to
publish close-spaced test data and occupied bandwidth data for transmitters.

The tests would have to be at 500Hz spacing on CW, not 2kHz. One new radio
about to be released has a ~2kHz roofing filter making it have really
inflated 2kHz test figures, but we really need 500Hz or less spaced
performance data for CW.

73 Tom