[Boatanchors] TV-RFI?

[Brian Clarke]

Hi Philip,

I reckon that EMR and EMC are some of our central concerns. We BAers tend to keep, 
use and maintain sets that are heavily into EMR generation.

The first question is, 

Is the noise radiated or conducted from the TV set?

If the noise is radiated, putting a filter in the TV set's antenna lead will do not a thing for 
your ham radio. You need to identify what could transmit an interfering signal - possibly 
the line oscillator, or perhaps a switched mode power supply. To fix radiated noise, you 
need to sniff around the TV set to find the source, create a Faraday shield around the 
source and ground it to the TV set's ground. You may end up having to spray conductive 
paint all over the inside surfaces of the cabinet, and use shielded power cable - then 
you'll have the problem of ensuring that the wiring board doesn't short out to the cabinet.

If the noise is conducted, the conduction may be in both the antenna lead and the 
power lead. To fix, you may need several ferrite beads over both leads, as close to the 
TV set as possible.

If the noise is both radiated and conducted, have you thought of buying a better make 
of TV? Actually, Philips sets aren't that bad - but the fact that you still have 300 Ohm 
twin lead antenna feed line suggests that this set was designed long before the word 
'interference' was ever heard. Perhaps you could create a Faraday shield completely 
enclosing the TV watching room? Shouldn't cost more than a small luxury car.

In Australia, a great deal of effort is being put into closing the door on EMR devices. 
Our local manufacturing industry has gone belly up in the face of Asian competition. 
We have been receiving the crap that other European countries would not accept. I 
note that the USA has been rather late coming to the EMC party - perhaps you have 
one of those VLS [Very Low Standard] Asian manufactured, but rebadged sets.

Another move in Australia is to outlaw all devices that remain on Standby - from an 
energy consumption perspective = very politically correct; bugger the maintenance 
perspective of finding and fixing soldered joints that have been thermally cycled many 
thousands of times. I suspect that your TV set is left on Standby, which is why you 
get rubbish from it even when it's off. Sorry, let me rephrase - you get different rubbish 
when it's in Standby mode.

73 de Brian, VK2GCE.