[RFI] I will have you arrested
Frank Haas KB4T
kb4t at arrl.net
Tue Feb 9 14:31:14 PST 2010
I am an interference investigator for a large electric utility in
Florida. If I see someone hitting a power pole with a sledge hammer
(or anything else) I call the police and have that person arrested.
Tampering with utility equipment is foolhardy, unlawful and doesn't
solve the core problem.
If you know what you are doing and trust your equipment, you don't
need to tamper with utility equipment. If you don't know what you are
doing and don't have equipment to trust, enlist the aid of someone in
your area who does. Call the utility and request an interference
investigation. Work with the utility to help them locate the problem
especially if they don't seem skilled enough to do it themselves.
(Interacting with the utility is an entirely new thread!!)
I have said this before here: You don't have the right to tamper with
utility distribution equipment. As has been pointed out by many here,
you can be injured or killed. Sure it's rare to get caught and rare
that things fall off poles but it does happen. The police in my
territory are happy to respond and arrest people tampering with
If I determine that interference is coming from your home rather than
from power distribution facilities near your home, is it appropriate
for me to start beating on your house to try and change or stop the
interference? Of course not. For this same reason, you don't have the
right to tamper with utility equipment.
In many respects, locating interference sources is much like regular
direction finding. You need equipment that can pinpoint the source.
You must learn to trust your equipment. Buzzing interference can come
from many NON-UTILITY sources. The biggest mistake many people make is
ASSUMING a source is coming from utility equipment. These days it's no
longer a slam dunk that the buzz you hear is utility-based. I'll
comment on this later in this note. Rule #1: Assume NOTHING! Trust
your equipment to lead you DIRECTLY to the source.
It's somewhat difficult to carry an 80 or 40 meter beam around. Small
loop antennas work well for sources that can't be heard much above 7
MHz. I use one I picked up at the Dayton Hamvention a few years ago.
Check out: http://www.g4tph.com/. A loop antenna coupled to a handheld
receiver capable of AM reception throughout the HF spectrum with a
usable signal strength indicator makes for a nice portable low
frequency DFing kit. http://www.homingin.com/joemoell/80intro.html
offers links to other low frequency DFing options.
I rarely need to use my loop set however. I use an Icom IC-7000
installed in my company truck with a Hi-Q 4/80 tunable antenna to
listen easily from 1.7 to 144 MHz. Starting from the customer's
location, I listen on the affected frequency (often in the 80M ham
band) and drive around in an expanding circle or square. When the
signal begins to max out the signal strength indicator, I tune to the
next higher harmonic or even higher and continue to drive. With many
sources and nearly all power line sources, I can hear the signal on
VHF. If so, within a short time, I'm parked within one pole or one
house of the source. Handheld equipment points me directly to the
source. If the signal is never heard much above 7 or 8 MHz the loop
set is broken out at the point where the signal strength maxes and the
foot search begins.
The vast majority of real power line interference sources can be heard
well up to 300 MHz as you get closer to the source. At VHF, it's easy
to pinpoint the pole. Once you have located the pole, leave the rest
to the utility. There are a few power line sources that can't be heard
above about 8 MHz even when you are close. Loop antennas have pointed
me to these sources. A power line source that is farther away than a
1/2 mile, may not be heard at VHF at the starting point. Instead, the
low frequency components of the interference are heard. Small loops
can point you in the right direction. As you travel in the direction
of the source, the signal strength will increase. As the signal gets
stronger listen higher and higher in frequency until you can point at
the source with a small yagi.
Once you have located the pole, it's next to impossible to determine
from the ground what might be wrong without very expensive specialty
equipment. 50% of the time, even the expensive specialty equipment
won't pinpoint the actual problem. I'm not a lineman. I don't climb
poles and I don't have a bucket truck. I do use binoculars to closely
examine equipment on a suspect pole. Sometimes I can see the problem
but very often I can't. Only a utility crew working with a skilled
investigator can take the right steps to find the source and eliminate
As the ham radio community begins to comprehend the spreading epidemic
of HF spectrum pollution that overrun the US, the ability to DF
interference sources is going to become ever more important. The
tsunami of garbage electronics flooding the store shelves and
streaming into your neighborhood will be much more of a problem than
the occasional power line interference issues that crop up. Keep in
mind that your utility cannot resolve non-utility interference issues.
For an illuminating introduction to this epidemic, take a walk around
your neighborhood with a battery operated handheld shortwave receiver
tuned to your favorite HF band. Be ready for a shock. You will
understand in short order why the noise floor in your receiver is so
high now. Power line interference pales in comparison.
Smacking a pole with anything is against the law and doesn't solve the
basic problem. Work with the utility to resolve the problem. Learn
their process and use it to your advantage. The problem will be
resolved safely and more quickly.
Want to take a sledge hammer to something? Replace your neighbor's
Whackycrap 5000 Deluxe with the spectrum-blanketing switching power
supply. Then use the sledge hammer to crush it so it can be mailed in
an envelope to the uncaring importer/manufacturer who designed it,
imported it and allowed it to pollute the spectrum in your
Frank N. Haas KB4T
Professional Interference Investigator
More information about the RFI