Braid Breaker
Although I cannot claim any originality for this little circuit ,it has never the less got me out of trouble a few times when the dreaded knock on the door comes.
I must admit that since cable T.V came to our area a few years ago, I have not suffered the T.V.I problems that I used to encounter, maybe I should keep my big mouth shut!
Anyway, the diagrams are self explanatory.
Just a little more to
this story. I had a problem with the circuit above, one day I started
getting TVI again, on checking the circuit I found the capacitors had
shorted out. This was a puzzle, so I started checking the coaxial and
what was actually coming down the cable. I set the transmitter in
operation and checked the cable with a field strength meter, the
needle nearly bent itself around the stop! Then I did a very silly
thing, I touched the connector on the end of the cable and received a
nasty little RF burn, no wonder the capacitors gave up the ghost.
Checking with a fluorescent tube confirmed there was a lot of RF
around the end of the TV downlead when it lit up brightly.
Incidentally, the TVI was still there when the plug was removed from
the video recorder.
After a little further
investigation I notice the TVI was only apparent on 40M, checking the
length of the TV downlead it measured 20M, a perfect half wave for 40M.
Six clamp on ferrite rings in the middle of the downlead cured the
problem. The point I'm making is putting braidbreakers in the
downlead will not always cure the problem if there is already a high
field strength at the end of the downlead, check other factors and
don't assume putting braidbreakers will get rid of a problem,
sometimes it doesn't.
I have been
experimenting with a couple of tiny loops of coaxial cable, these have
been very effective in eliminating television interference. They
consist of two small Faraday loops which are placed very close to each
other, they seem to give very little signal loss to theTV signal. The diameter of each
loop is about 20mm outside diameter, here is a picture of the Faraday loop
braid breaker.
