On Fri, 11 Sep 2009 19:13:15 +0300, Kostas Stamatis wrote:
>Any trick to try?
Study the tutorial below to understand the fundamental concepts,
then look carefully at your antenna system and the hookup to the
video screen to see how RF might be coupled into the unit, and how
it might be fixed.
http://audiosystemsgroup.com/RFI-Ham.pdf
Are your antennas close to the shack? They may be radiating
directly into the shack. If they are not close, perhaps RF is
coupled on the feedline. If coupled on the feedline, a serious
common mode choke at the feedpoint of each antenna may help. You
may also need a choke close to the shack.
Do you use a long wire or vertical that ends at the shack? That
would put LOTS of RF in the shack, and there's no good way to
prevent it with that kind of antenna. The only way to fix it is at
the monitor.
At the monitor, I would try chokes on both the power cable and the
video cable from the computer. These chokes cannot be simple
clamp-ons, they MUST be multi-turn chokes tuned to the frequency
range where you are having problems. See the tutorial for winding
instructions.
#43 ferrite materials (or equivalent by EU companies) will work
fine at 5MHz and above, but you will need Fair-Rite #31 for 80M
and 160M. There are lots of equivalents to Fair-Rite #43, but #31
is a new material developed by Fair-Rite and I don't know of any
equivalents.
73,
Jim Brown K9YC
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