"Glenn Richards" wrote in message
...
Rich Wilson wrote:

If you're going to upgrade your power cable you really ought to do it
all the way back to the substation, otherwise it's a bit pointless...

Well that was my initial thought... but apparently not.

In a conversation I had with a friend, we determined that power cables are
good at carrying low frequencies, and poor at carrying higher frequencies.
So RFI picked up at the substation won't make it to your house, but
interference sources in your house will cause RFI to reach your kit.


That actually isn't true. Until recently, when the amateur radio community,
via first the R.A. and then Ofcom, managed to get it stopped, there were
tests of a system call PLT ( power line transmission ). This system placed
RF carriers up to about 30MHz, onto the domestic mains supply. The purpose
was for data transmission of the broadband internet variety. However, no
matter how balanced the mains supply is, it still isn't good enough to
prevent common mode currents at these sorts of frequencies, and therin lies
one of the major problems with this technology. The whole mains supply
network, from the injection point at the substation, to your house, has a
tendency to radiate like a dammed great antenna, at times causing serious
interference to legitimate receiving equipment - and thats not a hifi, it's
a radio.

It was eventually determined that there were better, more efficient, and
less troublesome technologies available for broadband delivery, and dropped,
at least here, although I believe that there may still be some places in
Europe where the tests are still happening. Bear in mind also, that the
generating and distribution companies, use this, or a similar high frequency
technology, in-house to carry telemetry data around their grid distribution
network. So, just to recap, the mains power distribution system can
successfully carry HF, as well as LF, all the way to your house.

As far as interference escaping from your equipment goes, it certainly
shouldn't, under strict EU regulations. Any electrical / electronic
equipment sold in the EU, should carry CE certification, and one of the
requirements of this certification, is that the equipment does not either
send crap out onto the mains, above a certain very low level, nor directly
radiate it. Further, the equipment's normal performance must not be
compromised in any way, by the presence of high level RF or pulse
interference, either introduced into any outside-world ports, the mains
supply being one such, or by direct radiation.

So again, to recap. If the equipment is reasonably recent, and the
manufacturer is playing by the rules, it should not feed any crap onto the
mains supply. If your hifi manufacturer has played by the rules, his kit
should not respond to any such crap, that got onto the mains by any route.

All that said, there's no harm at all in helping your kit out by fitting a
surge arrester plug, which contains VDRs, and if you find a good one, it
should have RF suppression in the form of LCR in it, as well. Worth a tenner
for the surge protection at least, and the ' belt and braces ' for the
filtering that should already be in your kit, but I certainly wouldn't pay
any more. Even then, I would probably spend the rest of the week trying to
work out if my money would have been better spent on 4 pints ...

Arfa