>I have pretty much eliminated the local BC stations from my
receiver on 160 meters but can anyone please tell >how the
emissions from TV and computer monitors can be filtered out.
Bill,
The very same stuff that cures TVI and reduces chances of
lightning damage will also reduce RFI from the TV back to
your radio!
The bulk of radiation is *generally* from excitation modes
where the power line and some other connection are excited
in "push pull". In other words the antenna cable might be
one leg of a big antenna system, and the power line the
other leg of the antenna system.
This means high pass filters that pass LF signals straight
through, like MOST coaxial high pass TV filters, just let
the RF pour right past on the shield.
The most effective cures I've found for RF ingress and
egress in order of help are:
1.) Ground the power line safety ground to the antenna lead
ground (shield) at the outlet, and bring the cables together
from that point to the set. You can generally accomplish
this by buying a cheap "TV surge and lightning" suppressor
that has a three wire cord. Ohm the unit to be sure the
round power pin connects to the shields of the coaxial
jacks.
2.) Add a pair of .01uF UL/CSA/VDE rated power line bypass
capacitors inside the suppression device from each flat pin
power line connection to the grounded round pin. I have also
accomplished this by installing .01uF caps INSIDE a large
three wire plug, and plugging it into the strip. Be sure you
use common sense here to be sure no one can contact the
capacitors, and be sure to use capacitors rated for power
line bypass applications. They are flameproof and have
higher voltage rating than standard 1kV disc caps. Standard
caps should NEVER be used across power lines.
3.) If there are telco or other large wired connections to
the TV system (like a Satellite TV box might have) be sure
they are bypassed to the same common point.
4.) Be sure ALL devices at the entertainment hub are power
through the same outlet strip that powers the TV.
This works for computers as well. I could hear a neighbor's
computer from over two miles away until I bypasses the telco
line modem connection to the power line ground in one of
these strips. I did that by adding 1uH RF chokes in series
with the telco line jacks where they originally had small
fuses, and by adding a pair of .01 uF caps from each side of
the telco line to ground inside one of those lightning
protectors.
Hope this helps,
Tom
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|