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Re: Snow on telly, help needed !



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> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Snow on telly, help needed !
> Date: Wednesday, December 30, 1998 2:51 PM
> 
> Original Poster: "R.E.Burnett" <R.E.Burnett-at-newcastle.ac.uk> 
> 
> I thought that this must be due to noise being conducted from the TC
> back through the LIVE and NEUTRAL wires into the house,  so I took the
> following precautions:-
> 
> 
> 3. Is my ground sufficient and wired correctly.

>From an RF grounding standpoint, the ground may be pretty high impedance at
100 kHz. The rods are pretty short. What sort of wire/conductor are you
running to the ground and how long is it? Maybe you are radiating from the
ground wire?

> 
> 3. Is some filtering on the HV side of the transformer likely to help ?

You need to figure out if it is radiated or conducted EMI. Given all your
filters, I would think it is a radiated problem rather than being conducted
straight back up the line cord. However,  the filter does no good if the
wires "outside" the filter (say, those in the walls) are picking up the
radiated fields and then carrying them to the neighbors.

I think it also likely that the noise is being transmitted as a common mode
signal so any filters between the line and neutral probably won't do
anything.

You might want to get a portable battery powered AM radio and use it as a
"sniffer". It'll take two people, one to run the TC, the other to do the
RFI sniffing. Check and see if the noise on the radio increases when it is
near the power lines in your house or your neighbors.

Does the noise occur on a battery powered TV? That is, is it getting in
through the TV antenna, or through the TV power cord. If any of your
neighbors have SkyTV, are they seeing the interference: SkyTV is satellite
in Ku band where I can almost guarantee your TC isn't radiating, so if they
see intereference, it is getting there through the power lines.

I don't envy you in the least, because that whole EMC thing is tedious and
non-trivial.