[mythtv-users] Hum on analog audio to TV

[Allen Edwards]

>
>
> 2) Disconnect coax from TV.
> - This fixed the buzzing with the downside of losing live tv through the
> tv set.
>


Don't use an audio isolator as it is much more difficult to isolate audio
than RF.  Make an RF isolation device.  Just take two .01 micro farad
capacitors and connect both the center conductor and the shield through a
capacitor to the TV set.  There are a ton of ways you can make this.  I made
mine by taking apart an 75-300 ohm adapter and using a piece of coax as the
output instead of the 300 ohm lead.  Then I wrapped the entire thing in
aluminum foil well up the coax but not touching the braid.  This gave a
little extra capacitance and shielding to the thing without connecting the
shields together.  This will cost almost nothing to do but will take a
little time and you need to know how to solder and have the tools.  That is
the drawback.

It used to be you could take two 75 to 300 ohm transformers and connect them
back to back to make a 75-300-75 ohm thing that would isolate the ground.
 But, there are various ways to wire these and some don't isolate the ground
so they don't help.  If you have a couple of these and a ohm meter this
might do the trick, depending on what you  have.

I had this exact same problem and this solved it cold.


Allen
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