Originally Posted by wolffhans
I tried your sugestion to no avail. When I turn off the Zenith box with the analog TV on a loud (switch noise?) coinsides with the screen going blank. Sounds like the sound of an amplified arc. My house does not have a third (ground) conductor in the outlets. Can I tap one of the 110 Volt conductor to try grounding the coax cables?
Sure appreciate you replying so quickly.
Since you mention a coax, I presume you may be using an OUTDOOR antenna.
If so, the bottom of the antenna mast must have its own grounding wire and
at the entry point of the coax to the house, there must be a coax spark gap
arrestor, which must have a ground wire in accordance with local NEC requirements.
[PS: Attic and indoor antennas do not need to be grounded.]
Sooooo, the coax should ALREADY be grounded as part of the mandatory
NEC requirements, which will drain off static electricity build-up and provide
some protection against nearby lightning strikes....
And protect YOU against an insurance agent denying a claim if there's a "problem"....
Antenna installation guidance is given here (see Chapter Six):http://www.winegarddirect.com/pdf/manual_PR_models.pdfhttp://www.solidsignal.com/manuals/AntInstallGuide.pdf
The "antenna discharge unit" is a spark gap arrestor, aka "ground block":http://www.radioshack.com/product/in...entPage=search
Let me tell a little story first. While working on something electrical in my
daughter's mid-70s vintage track house I noticed there was several volts of AC
between "Neutral" (white) and safety ground (green)....by throwing switches
I traced it back to her old dishwasher (probably some EMI filters on the motor).
Okay, no big problem.....until much later I swapped in a motion sensor
porch light after doing the usual AC voltage safety check. I guess the
dishwasher pump finally came on, cuz I felt power (about 20 VAC) on the wires!!!
[Recently, her old dishwasher was replaced....hopefully no more problem.]
Moral of the story: The "Neutral" wire carries the RETURN current and hence
will be lifted ABOVE ground by V=IR. If you short "Neutral" to a ground other
than the originating transformer, you cause a ground loop in the power system,
whereby significant return current could be trying to flow "up" the coax:http://www.psihq.com/iread/strpgrnd.htm
Hence, various ISOLATION techniques are preferred to combat ground loops.
There are 120 VAC to 120 VAC Isolation transformers that can be used
on the TV and/or converter.
There are audio isolators for the L/R interface:http://www.radioshack.com/product/in...entPage=search
And there are coax isolators that work wonders for problematic cable systems:http://www.buy.com/prod/pico-macom-t...202749807.html
More info on coax isolators and power isolators can be found here:http://www.avsforum.com/avs-vb/showt...&#post10374027
It is important to determine whether the coax is contributing to the problem.
Can you use an alternative, temporary antenna and coax to receive DTV???
If you still see problems, it's not the coax.
If you have an AC volt meter, you can measure voltages between each
component and also to true ground with and without interconnecting cables
to help isolate the source of your problem....