> Think about that again. If you are listening to upper side
> band with a 3 KHz
> filter and you tune down 3 KHz in frequency with the dial
> you have moved the
> band pass the same amount lower in frequency as you would
> if you switched
> side bands with the side band switch. The only difference
> is that the
> carrier will be on the other side of the filter.
1.) The passband of the filter is 3000Hz.
2.) The offset is 300Hz from the carrier.
3.) The sideband switch now moves the start of the receiver
filter 600Hz lower than the start of the transmitter filter.
We miss the low frequency tone mixes that are often
problematic, and we also miss the high frequency tone mixes
that are close spaced because we never checked above the TX
signal.
4.) If I moved the receiver down 3000Hz and kept the same
sideband, that would not happen. The upper edge of the
receiver filter would hit the lower edge of the TX filter.
I don't see the big deal about moving the dial. Someone
could check by moving up the SSB filter BW and down. .
I'm not saying the test is useless, just that anyone
proposing or using a test should know what the test is
measuring and what it isn't measuring. It's always a good
idea to think about a new test procedure and understanding
how it all works and explaining limitations and what it
actually measures before going public.This is a pretty poor
method for over the air measurements because of noise
bandwidth problems.
73 Tom
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