> The tuner is the TenTec 247. The problem is everywhere on
the TV. The balun
> is a toroid wrapped in wire inside the tuner.
I've worked on or desigend a lot of tuners, but not that
one. I'd need to know more about the balun.
The TT tuners I could find use 4:1 baluns, and that
generally means they are voltage baluns or transformer type
baluns rather than transmission line baluns.
Voltage baluns are **very** susceptable to load impedance,
and fall out of balance very easily on real world systems.
They are the most load critical balun style we could use.
By far a much better balun is a choke or current balun of
1:1 ratio. It would have to be on a good ferrite core, not a
iron core (or worse yet air).
The correct balun on the output of that tuner can really be
just as good as a balanced tuner.
> > If the problem is channel specific, like say only on low
VHF
> > channels, you most likely have harmonic issues.
>
> Nope! It is on all channels.
Sounds like common mode RF. Harmonics are channel specific.
> > How is the twinlead routed? Is it kept away from other
> > things?
>
> Outside it hangs from the antenna, drops to about a foot
above the ground
> and comes into my window along with several pieces of
coax. It goes under
> my desk about 6-8 feet and wraps back to the top to the
tuner.
Ouch. How do you keep it isolated from the coax?
> I am considering the dual coax connection described in
another reply to keep
> the lead from having problems with surrounding metals.
Well, that might work. It won't be any less loss than moving
the balun outside the house and running a single line of
coax back inside from the balun to the tuner. Whatever coax
you use, use good low-loss cable.
73 Tom
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