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Re: Crosstalk on Mode B



Scott Townley wrote:

> I still have some crosstalk problems on Mode B.
> My setup is pretty marginal so no doubt that contributes:
>         10' tripod
>         12' yagis (linear, both vertical) on wooden crossboom about 6' separation
> I run the coaxes down the yagi booms to the crossboom, then across to the
> mast and then down the mast (as an aside, why does it seem more common to
> droop the coax off the back end of the yagi?).

First suggestion is to cross polorize them (make one horizontal).  That will reduce
the signal picked up by quite a few dB.  The theory behind dropping the coax off the
back of the antenna is that the coax in the antenna pattern will distort the pattern
(primarily with CP antennas).  The theory is correct, but how much of an effect there
is has been debated for years.  Personally I don't have the coaxes drop off the back
because mechanically it would cause all kinds of grief with my installation.  Here is
a photo:
http://home.earthlink.net/~k6ccc/Photo/Pics/SatAnt1.html

<snip>

> Is this a simple "2m Bandpass Filter" RF overload kinda issue, or is there
> more here than meets the eye?

That's likely it.

73
-----------------------
Jim Walls - K6CCC
k6ccc@amsat.org
http://home.earthlink.net/~k6ccc/
626-302-8515    FAX  626-302-7501
AMSAT member 32537 / WSWSS member 395


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