>From an RFI perspective at the TV receiver, there is a dipole
antenna the two halves of which are:
the braid of the TV feedline, and
the AC power wiring (hot+neutral in parallel).
The TV set sits in the middle of this dipole, and
detects strong RF fields, sometimes causing fundamental overload.
Since you moved your transmission feedline closer to the TV
feedline, you increased the coupling to this dipole.
You want to short out this dipole so that no RFI voltage
exists between the TV set and it's ground. It would be easy,
except... most TV sets do not have a ground connection in
the power cord (they use a 2-wire cord).
So here are the steps to take:
1. Purchase a AC power strip that has F-type connectors
in it. Get one that connects the F-connector shell to AC-power
ground. The TV antenna cable connects to one F-connector on
the power strip. You will need to make a short jumper (a
couple feet) to go from the other AC power strip F-connector
to the TV receiver.
2. You also want the type of AC power strip that uses
capacitors to bypass the hot and neutral wires to ground. This
puts the RF potential of the hot, neutral, and ground wires all
at the same value. These capacitors usually have about 1.6kv to
2kv rating so that voltage transients on the power line don't
cause them to fail (which could present a hazard). Of course
if the TV receiver had a three wire cord, this would become a
non-problem.
This setup shorts the braid of the feedline to the AC power
ground, and makes sure the TV set frame is AC grounded to the same
point. In essence you have shorted out the spurious dipole around
the TV set.
Make sure you shop around - there's some outrageously
priced AC power strips. You should be able to find one that's not
so pricey if you know what you are looking for and shop carefully.
-- Tom, N5EG
> I relocated the tower at my QTH. This put the feedline closer
> to my TV but located the antenna higher. The tower base is
> against the back wall of our house and a few feet from a 52"
> Mitsubishi projection TV fed by DirecTV. This TV is now
> experiencing what I think is fundemental overload. The picture
> is badly distorted and audio is present even with the TV muted.
>
> With my previous install I was able to eliminate TVI to this
> TV and some computer speakers by changing a bad feedline, or
> adding some chokes to speaker lines. The TV in the shack
> (fed by the same DirecTV) has never had TVI and it is next
> to amps, tuners, and a end-fed wire, so I don't think the TVI
> is due to spurs. The shack is about 50' from the house.
>
> My guess is I am going to have to add some serious RFI
> protection to the TV. Where should I start?
> John K5XTX
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