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Message-ID: <3.0.5.32.19990608151030.007a0100@zen.co.uk>
Date: Tue, 08 Jun 1999 15:10:30 +0100
To: rsgb_lf_group@blacksheep.org
From: "Alan Gale" <alan.gale@zen.co.uk>
Subject: Re: LF: Noise update
In-reply-to: <001901beb0b8$a947f950$ab97d28f@kate.geog.le.ac.uk>
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At 08:37 99/06/07 +0100, you wrote:

>I went out again with the Walkman, listening to a peak around 1340kHz, but
>still couldn't get a consistent fix on it. Walking around adjacent blocks,
>the strength and nulls vary in a confusing way, but it is certainly audible
>over a very wide area. What was especially interesting was that as I walked
>past the numerous telephone poles around here, the noise level increased
>significantly as I passed SOME of them. All the poles where the noise
>increased had a wire running down the pole into the ground, but NOT all the
>poles that had a drop-wire produced an increase in noise! Whether these are
>acting as radiators or merely 'receive antennas' I wouldn't like to say. The
>local digital exchange is actually on the corner of my block, but the noise
>didn't noticibly peak as I walked past it and the bearing I get from home is
>in the perpendicular direction!! I think this is going to be a tricky one to
>DF......

Hi John,

	I had a similar problem some years back, but instead of contacting
the RIS I got in touch with the local power company who sent along an
investigator from the Norweb Experimental Department. He connected a scope
to the mains via a special plug which 'blanked' the 50 Hz signal and 
revealed a regular spike on the mains voltage. He then produced a small
medium wave portable and a small 'satellite' type dish which was actually
an ultrasonic receiver, and proceeded to wander around the area in the 
direction of the local transformer. Results on the portable showed that
the noise peaked up strongly whenever we passed any of the streetlights,
and by using the ultrasonic receiver he was able to discover that the
culprit was actually a defective photoelectric cell on the top of one
of the lights. Some of the earlier models were prone to moisture ingress
and could produce thyristor type noise which was fed back along the 
mains supply to the transformer and all along the supply lines into 
the houses (and this was present even when the lights were off too!). 
The local council were contacted and the old lights replaced with newer 
ones and, touch wood, the problem has never recurred since. 

	It may be worth trying your local electricity company and seeing 
if they can help, since it's their responsibility to keep the mains clear, 
even if it's not a 'protected' band that's being affected. The difficult
part is often getting in contact with the right department in the first
place, though if you know anyone who works in the local company they may
be able to put you in contact with someone. Of course things may have 
changed since privatisation and de-regulation, but if you suspect that
it's mains borne it's well worth giving a try. I found the investigator
very friendly and helpful, and he even came round for a visit to the 
shack afterwards! :-)

	In the case of the ultrasonic receiver, I adapted my Bat Detector
and tried this out on a few high voltage power lines and they're great
for pinpointing arcing insulators etc. With a MW portable I could only
get a general bearing, but the ultrasonic receiver was able to pin the
arcing down to withing a few feet!

	Good luck, don't give up trying, I know it's very frustrating
but these problems can often be overcome.

	73 for now, Alan.

	
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 	From:		Alan Gale G4TMV 	
 	Location:	North-West England. IO83VP Lancs 53:39.3N 2:10.6W.		
	Equipment:	Kenwood TS830M + Converters + FL3. W & G SPM-3
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			a visit to my 'Beacons & Utes' website.
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