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 > > > > > > > > -- > View this message in context: > http://elecraft.365791.n2.nabble.com/Uninterruptible-Power-Supply-for-K3S-tp7619939p7619959.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to jstengrev...@comcast.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com