Over the years I've been contributing to the RFI email list, I have
mentioned nearly every tool I use to locate interference sources. I do have
a distinct advantage over the average ham because my employer, a large
electric utility in Florida, does equip me with the very best tools
available and has generously allowed me to buy and use additional devices,
antennas and receivers to do my job as efficiently as possible. I will list
my most used tools with a description and approximate cost. Hams can
duplicate the functionality of the more expensive tools with less expensive
The vast majority of my work involves locating power line interference.
Most power line sources are easy to pinpoint. Occasionally I will zero in
on a pole and not be able to pinpoint precisely what on the pole is causing
the interference. When I can't precisely pinpoint what on the pole is the
source, I write up a repair work order, meet a crew at the pole and we go
through a logical step-by-step troubleshooting process until we eliminate
the source. Locating non-power line sources to a building is usually pretty
easy as well. Finding a source within a structure is a little more
challenging because I must be careful using DF equipment inside.
In order of used most often:
1. *Icom IC-7000* ($1500 when I bought it) .5 - 470 MHz, all mode
transceiver - I can usually drive to within +/- 1 pole or one structure
using this radio. Antennas installed on my Ford E-350 work van include:
Hi-Q 4/80 ($695 in 2004) 3 - 54 MHz "screwdriver" style antenna, base
loaded 2 Meter mobile antenna ($50), center-loaded 440 antenna ($40). Hi-Q
is connected to the HF antenna jack. The VHF and UHF antennas are connected
to V/UHF antenna jack via an antenna switch.
2. *Radar Engineers M330* ($2300) handheld 320 - 360 MHz AM receiver
mounted on the end of a 5 element 300 MHz Yagi. (See radarengineers.com)
This receiver is optimized for the pulse noise produced by power lines. It
is very sensitive. I can hear weed whackers, lawn mowers, motorcycles, any
engine with a spark plug. I use this device to pinpoint a pole or building.
I have used this device indoors to find a variety of sources within a
3. *Radar Engineers Model 250* ($2500) handheld parabolic ultrasonic
pinpointer. This tool is designed to precisely pinpoint a source on a pole
IF, and that is a big IF, the source is arcing in a way that the ultrasonic
sound of the arcing is "visible." This tool is useful about 50% of the
time. Not all sources produce an ultrasonically detectable indication. When
the 250 can actually hear the arc, it's great. When the 250 doesn't detect
anything, we have to troubleshoot.
The first three allow me to pinpoint 90% of the sources I chase. Remember,
I chase mostly power line sources. But the utility is blamed for all kinds
of interference ranging from peculiar high pitched sounds to odd beeping,
warbling, rushing, popping, burping, swishing and other sounds from 10 Hz
to 150 MHz. So I have to be able to locate "signals" across that spectrum.
The most challenging sources are those that can only be heard at
frequencies below 8 MHz. On rare occasions, a power line source falls into
this category but the vast majority of these are consumer electronic
devices. My job description includes *proving the utility innocent*.
4. *Radar Engineers Model 242* ($4700) 1.8 MHz to 1 GHz "portable"
battery operated receiver with log periodic antenna that covers 300 - 700
MHz. I very rarely use this receiver and almost never use the antenna. I
generally use this receiver with the National RF Model HFDF Vector Gun
($330) 1.6 - 54 MHz active Loop antenna kit. I use this combination when
DFing 1 to 8 MHz sources. Very often, as I get closer and closer to a
source that starts out being detectable only at low frequencies, the source
becomes detectable at successively higher frequencies. At some point as I
get closer, these sources may be heard at VHF and that's when I switch to
the Radar Enginners M330. But this doesn't ALWAYS happen. I've had a few
power line issues that were detectable no higher than 8 MHz all the way to
the pole and more than a few non-power line sources that were detectable no
higher than 8 MHz all the way up to the structure. The latest version of
this Radar Engineers receiver (Model 247, I believe) has a color display,
more features in a smaller, lighter package. However, it sells for $5500 !
! ! !
When I get closer and closer to a low frequency source, the signal tends to
get stronger. If it still can't be heard above 8 MHz, but I know I'm close
AND it's inside a structure, it's time to switch to the
5. *Tecsun PL-660SLV* ($150) battery operated, AM/FM/SW/VHF Airband
AM receiver with simple attenuator, good signal strength indicator and
external antenna jack. This receiver is easy to carry and use with the
National RF HFDF Loop kit for indoor (and outdoor) pinpointing of low
These 5 items comprise my most often used interference search tools. The
functionality of each can easily be duplicated by hams without having to
spend a great deal.
When driving around in search of a source, the IC-7000 is the primary tool
tuned to a frequency close to the frequency reported by the complaining
party but I also have the AM radio in the dash tuned to 1710 and an Icom
IC-2820 tuned to 121.535 AM Mode. Listening across the spectrum can be
helpful. Occasionally, the source is first heard on the AM radio in the
dash. As I get closer, the IC-7000 tuned to 15.100 MHz will begin to buzz.
As I get within "viewing" distance of the source, the IC-2820 will begin
buzzing. When I can hear the source on the 2820 (or IC-7000 tuned to
144.200 AM Mode) I know the Radar Engineers M330 will zero me in to the
pole or structure.This is typical with most power line sources but
It is important to point out that having the very finest, most expensive
tools available won't guarantee success. The operator must know how to use
them. A thorough understanding of how radio signals behave when conducted
or radiated is essential. Direction Finding is not hard to learn but
practice is essential. Locating VHF/UHF sources is usually pretty easy
though there can be complications caused by reflections. Lower frequency
sources are the most challenging but practice reduces the challenge.
Patience and careful analysis of the data presented by the tools allows
sources to be found most efficiently. Perhaps most important: Keep an open
mind. Assume NOTHING! You can't see RF sources. You must trust your
equipment to take you to the source. Practice develops trust and
objectivity. Sure, the job is easier with great tools but the objective can
also be found with simple inexpensive tools.
Frank N. Haas KB4T
Utility Interference Investigator
P. S. I recently purchased an inexpensive SDR receiver ($165) to evaluate
its performance as an interference hunting device. It's a great receiver
particularly in the noisy work van. Unfortunately, the software is so good
at dealing with noise it simply doesn't work well as an interference
receiver. I'm still evaluating to see if the software can be configured to
allow me to hear pulse noise better. I like the data presentation of SDR
software. I'm hoping I can find a hardware & software combination that will
let me see and hear the sources I chase. More as it develops.
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