I would much appreciate some help in solving a noise problem which I
have. Please excuse the length of the following, but I think that I
need to explain the whole situation.
I live some 15km outside Sudbury Ontario in a rural area on the south
side of a lake which is about 15km long by 1km wide. My house is one
of about 15 permanent homes and 20 or so summer cottages along a 4km
stretch of lakefront all of which are fed by a single phase overhead
4kv line. There is an underwater hv feed from the north side of the
lake which is also pretty rural. Most, but not all, properties have
their own pole mounted transformer, and most of the cables to
individual houses are triples, with a few 2 wire and neutral, and one
or two (including mine) fed underground. About 1km to the east of me
the power feed changes and all properties are fed from a totally
separate line and direction.
The same poles carry telephone services, but there is no cable TV in
For the past few months I have been plagued by what I thought was
power line noise. This is intermittent on 160m (my main operating
band), but fairly constant on 14 and 21 MHz. By comparison, when I
first moved here a few years ago I wondered if my receiver was broken
because 160m in the middle of the day was totally noise free.
I have two verticals for 160. Both are about 50m from the power line,
but on opposite sides. I have a tribander about 25m, a 14-28Mhz trap
vertical about 80m, and a 7MHz vertical about 30m from the line. I
also have a number of beverages and EWEs. The former pass under the
The characteristics of the noise on 160 is that there is a frequency
range of between 10kHz and several hundred kHz which has impulse type
power line noise. However, at the edges of the this frequency range
there is some sort of switching signal which is a few kHz wide.
Outside this range the noise level is zero. The noise ranges from S8
to S9+ depending on the antenna I use but is loud on all of them. The
bandwidth and centre frequency of the noise varies both by drifting
and by sudden frequency jumps. Sometimes the noise is wideband so that
it extends down into the broadcast band and up to several MHz. On
increasingly rare occasions it is inaudible. When it first started
I am of the opinion that it was much worse during the day but now it
seems to make little difference.
On the hf bands the noise is much worse on the tribander than on the
trap vertical, and peaks when the beam is aimed at the
transformer/pole on my property. It does not appear to be
deterministic at all, but sounds like a typical ragged power line
noise. It seems to be there most of the time, and is typically S7 on
the beam. Of course, the pole is at a bearing of 45 degrees!
The noise is definitely (?) not coming from my house as it is still
there with the main breaker out and listening on a battery receiver.
My first attempt at tracking was with a small broadcast receiver. I
found I could only hear the noise at all if I was right next to a
pole. I walked along a lot of the poles and hit them with a
sledgehammer. Probably imprudent, but no change in the noise on any of
them. I did find one point where a two wire and neutral (low voltage)
section leading to a holiday cottage had the 240V wires twisted
together where one had come loose and where a tree had fallen on
another part of it. However, there was no audible noise there, no
obvious fire or heat, and I'm of the opinion that a short would
ultimately open the fuse on the input of the transformer.
My second was on 2m. Nothing heard at all anywhere.
I then made a large (1.5m sides) 160m loop, and started to listen with
the following conclusions:
1. The noise is definitely being radiated by the power line. It is
inaudible more than about 100m from the line.
2. The separate power line to the east (see above) is quite clean and
3. I am totally unable to get a proper bearing on the noise. I get
nulls, generally to the closest pole. The signal strength is fairly
constant along the line. Sense (cardioid) bearings all point at the
4. I would need to get several wavelengths from the line to take a
bearing which may point at the noise source. Unfortunately, I would
not be able to hear the noise at that distance no matter how large a
loop I was to construct! Also, it is physically difficult to get there
as it is virgin bush (or water).
5. I cannot imagine that the noise is being transferred along the
underwater cable, so it is presumably being either generated within
one of the 15 permanent homes or by the power or telephone line
equipment. It 'cannot' be the holiday cottages as these were certainly
unoccupied when the noise started.
6. The telephone line splits from the power line at one point and the
noise gets progressively weaker as one moves along the line. There is
a telephone switching (?) box where there is no noise, but there is a
strong unmodulated carrier on 1925kHz audible. However, this carrier
is not audible more than a few feet from the switching box.
I can think of no alternative but going cap in hand to all my
neighbours and asking them very nicely if they would mind tripping
their main breaker for a minute while I check for noise. I hate the
idea of doing this, especially as if it is one of them I then have to
ask them very nicely to trip individual circuits...
VE3ZI, ex G3RBP
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