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Date: Sat, 13 Oct 2012 20:53:25 +0100
From: g3zjo <g3zjo@psk31.plus.com>
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Subject: Re: LF: EMI...
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Hi Alan

Thanks for your interest and commiserations.

On 13/10/2012 19:24, Alan Melia wrote:
> Hi Eddie my commisserations on you interference, but can I refer you 
> to the regulations and in particular the "conditions of your (TV) 
> licence" "You must not cause undue interference to any other radio 
> television reception with your TV eqipment"
> Note it does not say "broadcast".
Yes but I think that the interference report form does not cover Amateur 
Radio and it is an unprotected service although Ofcom does deal with 
cases of interference due to faults.
> It is interesting you have interference at 500kHz but not 472kHz. This 
> almost suggests an older CRT system with 15.625kHz line scan coils. 
> Plasma interference is usualy from one of the PSUs and is radiated by 
> the braid of the aerial. A TV braid breaker will often cure this.
No way is this older CRT stuff, I know of 3 Panasonic Plasma TV's 
locally and get interference from them all the worse one, (closest) is 
through the lounge wall. Whereas the PSU' may radiate via the mains lead 
or antenna feeder Panasonic are well aware of that and have gone to 
great lengths with huge chunks of ferrite. The main radiation from 
Plasma TV's is directly via the screen, the plasma discharge, and 
spreads from LF to UHF, scan rates probably give rise to concentrated 
bands of interference which can be noticed when tuning the bands or a 
short wave portable RX, I assume this provides the 472KHz dip. It is 
really bad at 136 KHz see this picture from my gallery of filth. 
http://i221.photobucket.com/albums/dd243/radiotalk/zjo_grab600.jpg
I did try braid breakers on the main offender, mains and antenna feeder, 
there was no change what so ever.
The interference in the SW BC Bands is also imposed on my telephone line 
and those in the street right up to the nearest BT cabinet. 
Unfortunately BC stations can still be heard on a SW 'tranny' providing 
you are not too close to the source TV, within 10ft through a brick 
wall, so I cant claim BC interference.
>
>
> If you are on good terms with your neighbour it might be worth drawing 
> their attention to the licence conditions, and suggest they contact 
> their supplier, as you may have to make a complaint. The supplier 
> might be more "sensitive" than the neighbour, you may then suggest a 
> "cure" to try. The RSGB did used to stock these filters which are 
> normally used for VHF but are very effective for SMPSU radiation.
I am on good terms with them, I told them in good humor when they put 
their house on the market that I would be so pleased to see the back 
them with their Panasonic, unfortunately the recession meant there were 
no buyers. Still the new buyers could have 2 or 3 Panasonic's aye.
I contacted Panasonic on their behalf, to be fair they offered to 
investigate, however, I know that the set is no worse than any other 
example of the same model. In that case any call out would be chargeable 
and futile, a fact which they agreed.
>
> It  does work and these problems can be cured.
Panasonic Plasma problems are know worldwide they are the worst 
offenders among all the plasma bad technology. The only cure which my 
neighbor will not accept is a lead box around all 6 sides including the 
screen. The final 'cure' will be failure in time although prior to that 
I understand the QRM will get worse as the set ages, thankfully it is 
old technology and there is very little likelihood of a replacement 
being Plasma
>
73 Eddie