Notched noise tests are good for some things, and not for others. It is a
good test for multiple channels carrying similar amplitude signals of
constant level. It is not a good test for SSB transmitters or SSB/CW
receivers.
One serious flaw with a notched noise test is the lack of slow dynamic
variations in amplitude. This will mask what might actually be some very
serious problems. For amateur-type receiving use, a close spaced two-tone
test giving TOI and IM DR of lower IM products and gain compression is
generally all we need.
The real problem is the manufacturers (and ARRL) tend to focus on tests at
unreasonably wide spacing, where one tone falls outside the roofing filter
bandpass. Another is that transmitters are not tested for actual bandwidth
under real operating (modulation) conditions.
> broadband noise was applied. The noise was modified by
> notching out the bandwidth for one channel; i.e., essentially no noise in
the
> notched channel.
> -- measurements were made in the channel corresponding to the notch.
73 Tom
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