Noise can come from a number of different sources.
An example is the high voltage power line poles/towers
that criss cross the land. At certain points, there
are switch arms, usually located near power
substations. If the switch arms are not fully
seated, arcing occurs, creating noise.
Power transformers themselves do not cause power
line noise. The connections to them or the lightning
arrestor on the pole can be a source of power line
As wire pass next to and is held against the small
insulators on top of the pole, the wire holding
the power line against the insulator can be a source
Before you contact the power company about any power
line noise, it is best that you make sure your home
appliances, electrical wiring, or other electronic
devices are not the source of the noise. This will
require you to turn the main break switch OFF in
your home. Turn UPS systems, clocks, alarms, etc,
OFF. If the noise is still present you can be sure
the noise is not coming from you home. Make sure
ALL electric, electronic, and computers, including
laptops, UPS systems, etc, are turned OFF when
performing this check. If you call the power company
about power line noise, one of the first things the
trained technician will do is pull power at the pole
for your house to see if the noise disappears. Do this
BEFORE he arrives.
Always work with the power company, be friendly,
let them hear the noise on your ham station's
receiver, and show them what you have done to
locate the source of the noise.
The ARRL website has links to websites that can
help you with power line noise. http://www.arrl.org/tis/info/HTML/pwr-line-noise/ch5.html
Build yourself an Ultrasonic Power Line Noise Detector.
Arcing produces a low level audio sound that an
Ultrasonic detector can hear. The link below shows
how to make one. I built one and it does work!http://www.arrl.org/qst/2006/04/hanson.pdf
Power line noise may disappear on a rainy day,
when fog is present, or when ice covers power
lines. Moisture from rain, ice, or high humidity
completes the circuit, eliminating the arcing and
hence, the noise disappears. However, when the
moisture dries up, fog disappears, or ice melts,
the noise returns.
The power company's are required to keep their power
line noise to a minimum. Power lines fall under the
FCC's part 15 rules and regulations and must not
cause interference (power line noise). Power
companies can and have been fined heavily if they
refuse to fix or eliminate sources of power line
noise. Therefore, never think there's nothing you
can do eliminate the source of power line noise.
Having said that, don't think every case of power
line noise will be fixed in one visit by the
power company. Know that a power company may send
the wrong, unqualified, person to your house.
Describe the problem as a "noise" problem, not
an electrical failure in your home etc. This will
let them know they need to send a qualified person
who is trained in power line noise detection. I've
had this same thing happen to me, they sent the
wrong guy who was not trained. However, the power
company was quick to dispatch the properly trained