[RFI] I will have you arrested...
tomcox at iquest.net
Wed Feb 10 11:45:49 PST 2010
I replied on this subject to some technical correspondence in QST, back
in March, 2007. BTW: I got a few angry replies to this, which still
baffle me, but it probably just proves what Wayne Green used to say --
that Extra Class and some other, long-time hams tend to be sociopaths.
(NSD said that; not me!)
[QST excerpt begins:]
BAD POWER LINE NOISE HUNTING IDEA
I’ll bet you’ve been “whacked” with a lot of harrumphing over the note
from Al Lee, WA4EWV.
If not now, you probably will be. The advice to “whack the bottom of the
[suspect power] pole with the hammer” while listening to the AM radio
for the offending noise, will reliably give electrical utility employees
the vapors, and not without reason. The pole is usually the property of
the utility company that put it there, and whacking other people’s
property with a sledge hammer is bad manners, not to say illegal.
Besides, there are good reasons not to whack a pole suspected of
carrying noisy power line hardware. What if the offending hardware is
loose, rusted or lightning-damaged to the point where a whack will break
it? I don’t want to be under a pole with a sledgehammer when a 7,200-V
line or a 300-lb transformer breaks loose from its moorings and comes
crashing down at me.
I have poles in my neighborhood that are relics of the days of the Rural
Electrification Act of the Roosevelt Administration (Franklin’s, not
Teddy’s). Whacking one of those dried-out, quasi-petrified old geezers
could be the last straw for it. The electric company is responsible for
keeping its infrastructure in better shape than that, but guess who gets
the blame for a fallen pole or broken hardware, if it’s a result of a
misdirected effort at reducing power line noise? It’ll be the whacker,
not the whackee. Bet on it. And blame for utility company property
damage is the least of my worries, if the hot line falls on a person, a
house or a car, then or later, with predictable results.
Marv Loftness’s AC Power Interference Handbook is a superb source for
good advice on hunting down and dealing with power line noise — safely
and efficiently.3 Every radio club, if not every ham, should have a
copy. Read it before you go hunting, and save yourself some time,
effort, and needless risk.
Al’s advice on the doorbell transformer, on the other hand, is right on.
These critters are frequent offenders, and identifying one that’s gotten
noisy is doing the homeowner a favor, as well as the ham, since the
device can get hot enough to start a fire. Put down that sledgehammer,
and pick up Marv Loftness’s book. You’ll be glad you did.
I was a telephone line crewman for a while back in the ‘70s, and got to
be uncomfortably close to some really old-looking power line hardware,
and poles so shrunken they had daylight shining through the cracks. The
best way to narrow down the noise to one or two poles, says Loftness, is
to track it with a portable receiver that will listen at VHF, or better
yet, UHF, in AM mode. I have used a RadioShack handheld scanner that
will go to 800 MHz, and still do AM mode on demand from the keypad. It
even has an attenuator that is claimed to be 20 dB. I haven’t checked
the attenuation, but using it, and even disconnecting the duck antenna
when I get really close, I can pretty much nail the culprit.
The problem with using an AM broadcast receiver is that you are too
close to the strongest part of the line noise spectrum. That part of the
signal can couple into adjacent lines, and show lobes and nulls for a
mile or more from the actual noise source. The VHF or UHF portion of the
signal attenuates rapidly, roughly in proportion to the increase in
frequency. By starting out in the low-VHF range and increasing the
frequency as you get close, when the scanner begins to overload you
spend less time chasing “ghosts” and narrow the search more quickly.
This approach lends itself to using a portable, three-element beam on
UHF to do a quick scan of the horizon, but the gain of the antenna may
have you hearing more than one source (not uncommon in any area,
unfortunately), which can confuse things. The relative inefficiency of
the scanner’s duck antenna pays off, in that respect.
In summary: Get a scanner or dual-band hand-held radio that will receive
AM, read Loftness’s book, and leave the hammer and broadcast portable at
And, one last tip: Keep your eyes open. A first responder was killed
here [Muncie, IN] a couple of years ago because he walked into a
medium-voltage line that had fallen in a storm, and hung in some low
tree branches. The line was supposedly reported, but it remained there
until he touched it. It was a tragic waste, but it serves to remind
noise-hunters that their prey can be dangerous.
[QST excerpt ends]
73, Tom, KT9OM
rfi-request at contesting.com wrote:
> Message: 1
> Date: Tue, 9 Feb 2010 17:31:14 -0500
> From: "Frank Haas KB4T" <kb4t at arrl.net>
> Subject: [RFI] I will have you arrested
> To: <rfi at contesting.com>
> Message-ID: <005b01caa9d7$97f48e10$c7ddaa30$@net>
> Content-Type: text/plain; charset="US-ASCII"
> 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.
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