Thanks to all for your very helpful comments & suggestions.
John
WA1EAZ
> On Jul 11, 2016, at 5:18 PM, Mike K8CN <mike.car...@unh.edu> wrote:
>
> John,
>
> Power line arc noise can happen anywhere, even in a semi-rural area like
> your neighborhood (I used to live in Acton MA). There are many web
> resources for learning how to identify and track down power line arc
> sources. Here are some things I've learned by hard experience.
>
> A good, though not infallible, indication of a power line arc source for
> your noise is to check the bands during or shortly after a rain storm. Most
> arc sources are quenched temporarily by rain if they're exposed to the
> elements. When I first began tracking down noise sources at my QTH several
> years ago, I found that keeping a log of baseline noise levels (using the
> S-meter indication with the K3 in AM mode, widest filter you have) on all
> bands versus time of day and weather conditions was helpful in establishing
> any correlation with precipitation or neighbors' activities. I would also
> add comments about the qualitative audio signature of the noise ("buzz",
> "raspy", "intermittent buzz" - you get the idea).
>
> Simple preliminary source location techniques (once you've eliminated
> anything in your own home or yard) include using the AM radio in your car on
> a careful drive around your neighborhood to find candidate sources. This is
> not particularly selective - you'll hear other interferers in addition to
> true arc sources, and you'll want to tune to an unoccupied AM channel - I
> use channels high in the AM broadcast band.
>
> My preferred method once I've identified some candidate arc source sites is
> to use an inexpensive handheld VHF/UHF scanner with a rubber-duck antenna
> and a switchable attenuator. You don't need a fancy lab-grade attenuator -
> I find that a home-made 6 dB or 20 dB fixed resistor attenuator (50 ohm,
> shielded box) is sufficient. I tune the scanner to an open channel in the
> aircraft band (around 135 MHz; it automatically switches to AM detection in
> that band, which is necessary to do direction-finding based on signal
> strength - FM detection won't work), and walk around the suspect site. Turn
> off the squelch completely and set the audio gain at a fixed, comfortable
> listening level (I use open-ear headphones for safety as I walk on roads).
>
> I hold the rubber-duck antenna in the horizontal orientation and sweep it in
> an arc to either side of my body. The rubber-duck has a pattern null off
> the ends, and the reduction in audible noise is very evident if you're close
> to the arc source. You can resolve the 180 degree direction ambiguity of
> the null by using your body as an additional shielding attenuator - the
> difference in audio levels is your clue as to which null direction is the
> true one. You will find that you'll need to insert one of the fixed
> attenuators between the rubber-duck and the scanner antenna port if you're
> very close to the arc source - otherwise it will be difficult to perceive a
> null. I've used this technique successfully to locate multiple arc sources
> in my own neighborhood over the past few years. The one drawback is that one
> cannot hear the arc noise at VHF if one is more than a couple hundred yards
> from the arc source unless you use a small handheld Yagi antenna. It's easy
> to make a 3 element Yagi for VHF - there are several simple, inexpensive
> designs out there to be found.
>
> As Jim, K9YC will likely point out, you may also be hearing switch-mode
> power converters that have a much different noise signature than arc noise.
> If you can borrow a P3 panadapter from a nearby friend, it is an excellent
> tool for distinguishing types of noise. There are many other RF noise
> emitters - look at the archives of the Elecraft forum for some examples -
> the list of offending devices is too long to include here.
>
> One can, of course, purchase commercial DF'ing units that offer more
> features. However, you may already have the basic DF'ing tools in hand, or
> you may borrow them from a local ham until you find that you have a
> recurring need for this set of tools.
>
> It's likely that your local electric utility has a person trained in finding
> arc noise sources, but they love it when you can identify the specific pole
> on which you have found the likely source!
>
> 73,
> Mike, K8CN
> Durham NH
>
>
>
>
>
>
>
> --
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