[net.ham-radio] Reverse TVI comments

rjr@mgweed.UUCP (Bob Roehrig) (08/22/85)

I have had the same problem with reverse TVI. In my case, the problem set
is my own RCA XL-100. While it has a power transformer, the chassis is not
isolated from ground. The primary has an autotransformer connection (about
200V I think) that is used for powering the deflection circuits so one side
of the line cord connects to the chassis. Besides this, the case is non metallic
and offers no shielding at all. 

A good deal of the radiated horizontal deflection signal is via the AC line
and a good grounded line filter will help. You did not state if the TV sets
were using twin lead or coaxial antenna systems or connected to a cable
system. Mine is fed with 300 ohm line and a TVI preventing type hi-pass
filter in the lead-in helps reduce the radiation from the set also. I would
think that 20 meter traps in the sets antenna system might help too.

Bob K9EUI