Alan, et al.
As an RFI/power line noise (PLN) ARRL Technical Specialist, when Mike Martin
speaks, I listen. Mike has decades of real-world experience with these matters.
The following may help with some of your questions:
The Radar Engineers RE250/251 ultrasonic pinpointer must have line of sight to
the sparking hardware to detect it. It is not without limitations, and a good
RFI/PLN investigator knows the strengths and weaknesses of each of his or her
tools. For example, the pinpointer cannot detect internal sparking of lightning
arresters which cause RFI. Also, the pinpointer has a very hard time
pinpointing sources that are located under PVC wildlife protectors. Finally, in
my experience, the pinpointer is ineffective with sources under about 12 kV.
(e.g, 7.2 kV, 4.2 kV, and 2.4 kV lines)
The Radar Engineers’ Model 250/251 and the MFJ-5008 are so totally
different that they are incomparable. The Radar Engineers 250/251 uses radar
principles at 20 kHz to detect sparking hardware, thus the company name. The
250/251 has a very wide dynamic range, unbelievable sensitivity and filters to
discriminate between powerline noise, corona, and other pulse type noises. The
MFJ-5008 does work, but uses heterodyne principles at 40 kHz, and has less
sensitivity and filtering.
A powerline noise survey of a utility’s “grid” can be made
quite expeditiously using a Radar Engineers Model 243 and a car or truck
mounted antenna. In fact, there is a GPS-linked software program that plots PLN
RFI “hot spots” on a street or satellite map.
I have used the Fluke ii910 acoustic imager for about 4 years now to help find
power line noise RFI. The Fluke is indispensable for documenting the RFI source
hardware for utility crews. They understand a picture that shows both the RFI
and the defective hardware. A picture is worth a thousand words as they say.
However, like any tool, the Fluke has its own limitations, strengths, and
weaknesses.
I have not used IR cameras, and have no practical experience with them. I have
heard they are of very limited use for detecting sources on distribution lines
and “backyard” power lines. This is because the small sparks on the
Clevis pin of Bell insulators or tracking on a post insulator do not generate
much heat. I suspect they might be useful to locate hot spots caused by
dissimilar metal corrosion or other corrosion on clamps, etc. This is because
resistance to current flow causes heating (e.g., a power resistor).
The Radar Engineers M330/331 uses a 4-element 330 MHz beam antenna and tunable
receiver with a patented ignition noise filter to discriminate between
powerline noise and other pulse type noise sources. I use a combination of HF
loop, HF directional loop, (ARDF loop) VHF dipole, 3-ele VHF beam, and 5-ele
UHF beam to help locate noisy poles. Other RFI investigators have had great
success with Flag Antennas. (DX Engineering)
Hope this helps.
Chris Parker AF6PX
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