[RFI] Question on HF loop for tracking line noise
eedwards at tconl.com
Sun Feb 19 20:20:58 EST 2006
That's why, as I mentioned previously, one of the guidelines in the RFI
books and followed by good RI investigators is to track the noise at the
highest freq at which the noise can be rcvd moving higher whenever the noise
gets stronger. Tracking noise that's too strong can become very frustrating
at times depending on the system architecture.
Also keep in mind that some of the noises you may find might not be
impacting your station location (if fixed) due to the Standing Waves I
mentioned. That usually the case when a ham has tracked "a noise" in his
neighborhood, calls the power company, they come out and repair the source,
and there's no change to the original noise source.
Whoops! Wrong source. Do this too many times, and the power company will
think you're a goof ball and will be slower to respond. This is where the
power company should use Loftness' source I.D.ing techniques on a storage
scope to track the actual problem source affecting the ham. However, not
many of them do. So it's up to the ham to sort it all out if possible.
I recommend always finding as many strong nearby sources as possible before
calling the power company. Do whatever you can to sort out which ones you
can hear and which ones you can't to prioritze them. Then call the power
company with the listing. If they cannot determine which one is the
problem, tell them to fix them all starting at the top.
73, de ed -K0iL
From: Tom Cox
One problem I see with tracking line noise using any HF DF-ing scheme is the
ease with which the HF component of line noise couples and re-radiates from
power lines hundreds, or even thousands of yards from the source -- with
lobes and nulls all along the way that make you think you're hot on the
trail when you're not even close. A sharp HF antenna might find several
apparent lobes for a single noise source, leaving you no closer to the real
source than walking under a mile or three of line carrying an AM BCB radio.
The point of refining the search using an AM-capable receiver at VHF or UHF,
as I understand it (and as it is described in Marv Loftness's book, POWER
LINE INTERFERENCE HANDBOOK), is the increasing resolution as you move to
higher frequencies. If you lose the source when you move from 40 M to 2M,
maybe it's because you aren't as close to the source as you thought you
were. It may be helpful to move from 40M to 10M, for example, refining the
location, and then into the low VHF range, as you get closer, and up into
higher frequencies, etc.
If you keep getting ambiguous locations at a higher frequency, maybe you
have multiple sources. Loftness and others have said that is very likely,
anyway, since the conditions that produce arc on one pole probably apply to
all poles in a system that are of the same vintage.
Pick one source, narrow it down, and then go to the next one. Be ready for
peeling back the layers of an onion, finding and quieting one source, which
allows you to hear the next one, etc., ad nauseum. And, be willing to accept
something short of perfection, unless you want to spend all your time
hunting line noise, and no time operating.
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