I think based on the work by SM5BSZ i think a good standard
to aim for
in ham transmitters would be the FCC's Part 80 maritime IMD
mask
standard. It requires 3rd order products to be down 30 db
as referenced
to 1 of 2 tones. The standard addresses the specific
issue of wide
band splatter in that the standard requires higher order IMD
products
of the 11th order to be down 75 db. This is even more
stringent than
what SM5BSZ wishes for. I think from memory it was
something like 80 db
down at 20khz that he was calling a "clean" transmitter, i
cant recall
what reference he was using whether it was PEP or below one
of 2 tones.
Craig
VK3HE>>>>>>
The high-phy audio boys aren't going to like this, because
to meet that spec we would have to restrict the amplitude
level of the lowest and highest modulating frequency as well
as make sure exciters were cleaner.
Otherwise we would have to toss out the -80dB at 20kHz
concern, and if we do that we might as well let everyone be
a bandwidth pig whether from class C splatter or Ted Baxter
syndrome. Doesn't matter how it gets there if it is out
there.
What we need to do in amateur service is just set a
bandwidth limit. If you are below such a signal level at
3kHz on SSB, you can be doing anything you want in that
3kHz.
The ARRL's BW proposal was a good basic idea.
73 Tom
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