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Author Topic: 10 Meter RFI in northeast Pa. Anyone else?  (Read 1437 times)
KB3BTO
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Posts: 41




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« on: January 02, 2010, 02:49:32 PM »

My QTH is in grid FN11 approximately 25 west of Wilkes-Barre in the town of Shickshinny. I have been experiencing irregular but severe RFI each of the past 2 years and now again this year. It results in a S-8 RFI on 10 Meters. Specifically, the RFI increases in intensity from 22MHz up to 29MHz. It usually peaks at 27/28 MHz and is present in the day time only.
 The RFI begins each year in late December and continues until spring. It tends to decrease in intensity until it disappears in late spring.
 I sometime get spark-gap type spikes and other times there is a radar-like sweep/pulse besides the very loud static.
 Interestingly, the RFI will cease in the spring when it rains. (spark gap?)
 I've done the usual checking but I'd like to hear from any hams near me that are experiencing the same thing.
 TNX Charlie Shaw KB3BTO cshaw@epix.net
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KB3BTO
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Posts: 41




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« Reply #1 on: January 02, 2010, 03:03:08 PM »

Here's more info: I using dipoles, I've already unplugged everything in the house, I've flipped circuit breakers, the RFI is on both rigs but is stronger on the dipole closer to the power line, I've been working with the local utility company, I've considered the possibility of Christmas decorations causing the RFI but then why would it last until late spring?
  Also, the RFI appears to begin around 0800 which would indicate to me that it's not power line specific but that some electrical device is being turned on and generating the RFI, but what?
  Perhaps the power lines are picking up this RFI and carrying the signal, but what's the origin?
  I'm just curious if this RFI is being experience by other local hams.
 
  Charlie Shaw KB3BTO
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WB5JEO
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« Reply #2 on: January 04, 2010, 08:47:21 AM »

When something like this begins suddenly, as I assume it did two years ago, I first think of defects in the electrical distribution system. The daytime aspect may involved electrical demand. Demand typically is rising sharply by 8 a.m. and has fallen back to the 8 a.m. level by about 5 p.m. Which makes me think of a defect that produces an arc under the heavier load. I'm not sure about he seasonal aspect. Your month-to-month precipitation averages are remarkably similar through the year, but other things can be involved, like processes that eject particulates during some seasons and the intensity of rainfall events in some seasons. I once had a recurring problem caused by lint from a cotton gin that accumulated and formed arc paths across insulators until a particularly heavy rain or a series of more gentle rains washed it away, and it didn't return until the next ginning season. It was a problem across a wider range of frequencies, but it originated within 100 feet of my antenna. Yours may be radiated by a floating segment of wire that happens to be resonant at about 28 mHz. That can be anything, including a broken ground lead on a pole. Sounds like it's time to mount a hunt.

Of course, there can be other odd combinations of factors. Daytime only might suggest a solar charger or associated inverter, with temperature or pollution effects providing the seasonal aspect. Come to think of it, had I been close to the cotton gin itself and it happened to have a noise source in the equipment, I would have heard it only during the ginning season, it would have been daytime only, and it might well have decreased over time, since there's a lot of throughput early on and less as time goes by. Any kind of seasonal activity like that in the area?
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KB3BTO
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Posts: 41




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« Reply #3 on: January 05, 2010, 05:38:23 AM »

Thanks for the idea about the relationship between an increase of power usage and the RFI beginning on or about 0800. I will include that factor in my "hunt."
  There is a high school approximately 1 mile from my shack and a diesel engine repair shop half that distance from here. All are being considered as a possible source.
  We had almost daily showers in the spring of last year and that would put a stop to the RFI, but it made it difficult for the utility company representative to set up a visit with his equipment to pinpoint the RFI source. The one time that it was dry, and he rounded up his gear and came out here, the RFI stopped as he was enroute. Go figure?
  I must state that the utility company rep is being very patient and helpful, so that 's a plus.
  Also, the RFI is much, much stronger on the dipole that's 20 feet from, and perpendicular to, the power line running to the house then it is on the other dipole that is about 50 feet from the power line. In fact, the farther dipole often is left unaffected.
  There was no RFI this morning at 0740 but it's beginning to build of as 0800. Here we go again.
  Thanks for your constructive input.

  Charlie Shaw KB3BTO
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KB3BTO
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« Reply #4 on: January 11, 2010, 06:47:26 AM »

This past Saturday, 1/9/10, I had HEAVY RFI on both of my dipoles. My 10 meter dipole was picking up a S-10 reading at 0950 EST on 28MHz using my TS-940 radio and my 20 meter dipole was picking up a S-7 reading at 28MHz using my TS-2000 radio.
  The dipoles are parallel to one anther but are 50 feet apart.
 Also, for the first time this year, I had strong RFI at 14MHz resulting in a S-3 reading on my TS-2000 using my 20 meter dipole but there was only slight RFI heard and no meter deflection using my 10 meter dipole on my TS-940 radio.
 I had a weak hypothesis that the RFI was being caused by a next door neighbor who is currently on vacation, but, after the RFI experience of 1/9/10, I would have to eliminate that from serious consideration.
 I also discovered that switching the rig from SSB to AM reception results in a greatly increased effect of the RFI signal on both the speaker and the SM-220 station monitor scope. Hopefully, this will make it easier (?) to find the source of the RFI when I meet with the utility company representative later this week.

 Charlie Shaw KB3BTO
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WB4BYQ
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Posts: 179




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« Reply #5 on: January 11, 2010, 12:30:15 PM »

I would like to see you use some fox hunting ideas to your rfi problem.  use you radio in the car with a cb whip mag mount ant, or something along that order and ride around the area and listen on 14, 21, 28 mhz where the noise is the greatest, turning on the att on the radio to reduce the signal and see if the problem is not coming from a neighbor thur the power line drop from the pole to the house. As you ride around look for the poles and drops, and notice if the level goes up and then down with the attenuator turned on. You will find more information about the noise when you travel the area.
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KB3BTO
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Posts: 41




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« Reply #6 on: January 11, 2010, 12:55:53 PM »

Thanks for your suggestion but the representative from the utility company is coming out tomorrow with a trunk full of sophisticated "sniffing" gear.
  He's starting by checking my rigs and antennas and then branching out from there. Hopefully, he will be able to identify the source and we'll take it from there.
  My only concern right now is that the RFI will be present when he gets here.
  73
  Charlie Shaw KB3BTO
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KB3BTO
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Posts: 41




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« Reply #7 on: January 13, 2010, 06:29:50 AM »

The utility rep arrived as promised and got to experience the RFI conditions first-hand.
 We hooked up his "RFI Locator" - a very nice piece of equipment - to my dipole and observed the twin peaks of RFI on the display screen. These peaks were similar, but more refined, than the display on my SM-220 scope.
 He spent all day either in my shack or roaming about the local area searching for the source but, sadly, was unable to pinpoint an exact location.
 Apparently, the "twin peaks" displays are similar to, but not exactly, what his reference book indicates would be a classic power line related problem.
 Perhaps it is a piece of power line equipment that is in the process of failing but has not suffered a catastrophic failure as of yet? Only time will tell.
 The hunt continues, and so does the RFI. (%#@?^&%$!!!)
 
  Charlie Shaw KB3BTO
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KB3BTO
Member

Posts: 41




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« Reply #8 on: January 31, 2010, 02:26:19 PM »

Here's an update: the RFI was gone for approximately 10 days and then came roaring back. From what I've been able to hear on my rig in comparison to sound bites on the internet, it's definitely power line RFI.
  Additionally, the wave form display on my station monitor looks something like this when I put the radio into AM reception mode: (...||...||...) There are twin, very tall spikes stacked closely together when the RFI is BAD. When the RFI is overpowering and a S-8 on my strength meter, the wave form looks like this: (..|||||...|||||...|||||...) There are 5-7 very tall voltage spikes stacked closely together.
  The utility company rep has been very patient but the intermittent nature of the RFI has made it most difficult for him to be in this area at opportune moments.
  Sadly, I find myself wishing that the RFI would be constant enough for him to come out at any time and go on the hunt.
  Whatever the exact cause of this RFI, it's focused right on, or about, 28MHz and comes and goes at all of the wrong times.

  Charlie Shaw
  KB3BTO
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