Jim, Jim, Tom, Mike, et. al.:
>Lets put some numbers to the requirements, just for grins..
I don't recall where this thread started, but I think it was someone
looking for magic filters for in-band FD applications.
However, if you start with all monoband antennas, and known quiet rigs,
that's a start. Then, place all antennas so their side nulls are facing
each other, when in the most likely direction.
You might get 20-30dB nulls from each antenna, and if you were lucky
enough to get them to line up, they might provide 40-60dB isolation,
right there. Depending on spacing distance. Let's assume 40, for
discussion.
Then, let's use dunestar bandpass filters on all rigs. That will
knock down another 25dB on out of band products. Let's assume 20, for
discussion.
We're now -60d, and in FD, if you do that from 100 watts, 100x10^-6 is
100 uW. If you assume best case conditions, you're probably down another
25dB from there, or half a microwatt more or less. Surely audible, but
in practice, probably not louder than real signals from the front of a 20m
yagi.
None of this will help you IN band. But I've been able to run ssb & cw at
the
same time, using 4 el 20's @ 70' spaced by about 400', with no difficulty
whatever.
The real issue becomes one of station management and objectives, as I
indicated
in my last post. Since you can't isolate all rigs perfectly, on all
possible
combinations of frequencies, some discipline is required if score is not to
suffer.
I recall planning meetings where guys wanted to run qrp, psk, rtty, and 160
meters.
When you look at the setup work and isolation issues vs. numbers of
potential contacts,
you're better off NOT doing those things, taking a good nap, and being
rested to
do battle on a run station. My point, I guess, is that there's no point in
fighting
physics when operational issues dominate the equation.
N2EA
jimjarvis@ieee.org
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