[mythtv-users] Hum on analog audio to TV

[Allen Edwards]

On Wed, Oct 22, 2008 at 3:35 PM, Allen Edwards <allen.p.edwards at gmail.com>wrote:

>
>> 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
>
>
> If  you don't want to make one I think this device will work:
https://www.tselectronic.com/gc/video/surge_block.html
It is the one on the right which I think is the more expensive one.

Here is a source in the UK:
http://www.chsinteractive.co.uk/electrical-components/aerials-accessories/cable-ground-breaker/coaxial-ground-breaker-feed-thru-surge-protector-coaxial-plug-to-coaxial-socket-black.htm

Allen
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