[RFI] Radar Engineers RFI Analyzers

Frank N. Haas KB4T utility.rfi.pro at gmail.com
Mon Dec 24 13:17:02 EST 2012

What setup gives you the most versatility and ease of use?

I work for a large electric utility that has equipped me with every
useful tool I need to track down sources quickly and (relatively)
easily. In order of "used most frequently" I would list:

Radar Engineers M330 handheld 320 - 360 MHz receiver on the back end
of a 5 el yagi (VHF RFI pinpointing)
National RF HF Vector Gun with the Radar Engineers Model 240 (HF RFI
locating, not always pinpointing)
Radar Engineers Model 250 (pinpointing sources on poles - only
effective 40% of the time but I always try)
Grundig Model G4000 handheld AM/FM/SW receiver
ICOM IC7000 & Hi-Q 4/80 3 - 54 MHz "screwdriver" antenna on back
bumper of work van (Gets me to within +/- 1 pole or house of source)

I use a 100 MHz RIGOL (brand) oscilloscope connected to the work van's
AM radio speaker audio output to get close to, but not necessarily
right on top of, a .5 to 1.7 MHz source. It's impossible to accurately
measure by ear the changes in audio volume coming from the truck's AM
radio. The scope makes it easy to measure the levels. This process
usually gets me to the block if not within a few poles or houses of
the source.

The most challenging sources for me are the lowest frequency (.5 to 2
MHz) HF sources that are 1 to 3 miles away. At the affected party's
location, the RFI may be strong on the well-equipped base station but
on my portable equipment the signal tends to be pretty weak. Great
care and patience is usually required to track down these sources from
a distance. The National RF HF Vector Gun and the RE Model 240 work
very well for these sources. As I get closer to the source I listen
higher in frequency. In fact, I always listen to the highest frequency
at which the RFI can be heard. The higher the frequency, the easier it
usually is to locate the source. Many of these sources can be heard at
VHF when you get very close and the M330 is usually effective at
pinpointing if this is the case.

The IC7000 and Hi-Q 4/80 often get me in the neighborhood. It's
relatively easy to hang the 240 around my neck and search with the
National RF HF Vector Gun to find the general area of the source. All
of the other handheld tools get me to the source. I follow this
pattern 90% of the time.

Essentially, I like tools that are simple and effective. Since I get
paid to find RFI, time is money. Sometimes searches can be very time
consuming because of distance and reflections. Luckily I'm able to
work methodically, trusting my equipment solely and completely to take
me to the source. Read that last sentence again. I trust my equipment
solely and completely to take me to the source. I don't speculate. I
don't guess. I don't care what the RFI sounds like. I just DF it.

All the chatter on here about what something sounds like just makes me
laugh and shake my head. I see such discussions as a complete waste of
time. Yet they are so frequent that I've given up responding to them.
When someone spends any amount of energy trying to compare sounds, I
know they are not properly equipped or don't really understand how to
locate a source. Once you find a source, you will know what it is. So
many sources sound alike that comparing sounds is simply an exercise
in futility.

For years I have said here and in other venues that direction finding
skills and the tools to use them are the most important aspects of RFI
location. While I have great respect for the concepts presented in the
Loftness text, I view some of the equipment lash-up suggestions as out
of date. However, I understand that everyone doesn't have access to
the same professional tools I do. Creativity and ingenuity are often
necessary. Time invested in equipping oneself to chase RFI in a
specific frequency band is much more productive than comparing sounds
in the hope finding the source with your eyes.

Superior DF tools and skills allow one to locate sources as quickly as
possible. The tools are not cheap and cheap tools are rarely
effective. I have long suggested that local ham radio clubs combine
resources and funds to equip themselves well and master the use of the
best tools. The RFI problem is only getting worse. Hams are the most
susceptible to RFI. Power line sources are no longer the most
frequent. The tsunami of garbage consumer electronics will present RFI
challenges for generations. Ham clubs are the best choice for
assembling and mastering the tools that have become increasingly
necessary for hams to survive in today's ocean of RF pollution.

Good luck!

Frank N. Haas KB4T
Utility RFI Investigator

More information about the RFI mailing list