[RFI] RFI with sound bites
Gary at ka1j.com
Mon Dec 3 00:48:25 EST 2012
Thanks for the replies.
No, not windy at all when I recorded that. Might have been a bit of a
breeze but nothing to noticeably move branches.
I heard something last night during the contest that was more like
the woodpecker than anything I have heard since then. It was very
broadbanded and went onto 80 meters as well. Almost like a machine
gun & with the CW filters it sounded like a drill hammer in a tunnel.
I was wondering if there was a military test going on & asked on the
topband list if anyone heard it around 2AM EST last night but no
replies so it must have been local. I'll post that recording too but
don't have the time to do it now, must sleep.
No beam here, only have the HI-Z triangular Rx array & various wire
antennae strung up in trees with a common radial base & remote
switching unit to select the one I want.
Air band receiver? Which frequency are you thinking of. There is a
multi band small portable receiver here with short wave & maybe 7
I can hear the interference now on 160 but it's spurts, not
repetitions long episodes of the same amplitude. It lasts maybe a
second at S7 and then nothing with S0 till the next spurt 5-6 seconds
later. It is heard with a smaller intensity signal as I go up in
frequency. I can barely tell it's there on 30M and it's a quiet band
with little background noise. 20M has a loud background noise with
hints of the QRM. 24M through 6M are dead quiet. 10M is almost the
same quiet as 24M-6M but I can hear subdued bursts.
I'm of course happy to walk around at night following the power lines
but as Lee mentioned, Amtrak is next door and they have 10' hurricane
fence on both sides to prevent people from being hit by the high
speed cars. It is electrified rail but has been for many years
without this QRM. The power company I can perhaps expect to get a
crew to fix an issue. I'm not so sure about Amtrak.
What frequency should I look for in the portable radio?
> Was it windy? It sounds like arcing on a power line. I had something
> similar here, it was loose hardware on a old power pole, it made a
> buzz buzz random noise when it was windy. When I had it narrowed down
> to the pole all I had to do was push on the power pole a little and
> the noise was there. Power co. fixed it. I would try to get a
> heading on it using 10 meters and a beam if you have one. Walking the
> power line with a air band receiver would get it narrowed down. If
> it's real strong at your QTH on 10 meters then it might be close.
> Good luck.
> Dale, k9vuj
> On 01, Dec 2012, at 23:14, Gary Smith <Gary at ka1j.com> wrote:
> > I'm having a horrific level of QRM which seems to bother 160M and
> > 30M the most. My inclination is it's a street light that is causing
> > the noise as I often notice it at gray line times. I was working the
> > ARRL 160M contest and it started up around 11PM local time. It was
> > sufficient to ruin any chance of QSOs during the contest so I taped
> > it first with a 200Hz filter on CW and you can hear what it sounds
> > like to me. no file is more than 400k in size.
> > Its often a repetitious rhythm of buzz that happens 2-3 times per
> > second with occasional dead times of several seconds and then back
> > to it again. Sometimes it is persistent for several minutes and then
> > back to the buzz-rhythm.
> > Here is a view of the QTH. My house is the last one, at the end of
> > the road & next to the rail line. I am sandwiched between two state
> > parks. Other than Amtrak being beside the house and the people on
> > the road south of me, there is no other house or signal generation
> > within a mile. Mt antennae are wires in trees next to the salt
> > marsh.
> > http://tinyurl.com/cy7zv7h
> > Here's #1 with the 200HZ filter during the contest at the bottom of
> > the band and then tuned below the ham band for no CW in the
> > background for comparison.
> > http://doctorgary.net/1-QRM-2.8KHz-CW-filter-160M.mp3
> > Then I recorded the same conditions on LSB with a 4K filter. I did
> > the same and dialed below the contest for comparison.
> > http://doctorgary.net/2-QRM-4KHz-LSB-160M.mp3
> > So as often happens, it stops for no known reason. I went outside
> > with the AM and got half way down the drive and it stopped. I saw no
> > street light flickering. I came back and made a similar tape with
> > 4KHz LSB and you can hear the difference in what I can hear. I also
> > drifted below the band for comparison
> > http://doctorgary.net/3-QRM-gone-4KHz-LSB-160M.mp3
> > Sat at around 7 AM it started and I had to stop calling CQ and quit
> > because I couldn't make out anyone who wasn't extremely loud.
> > Any idea what this sounds like it might be so I can deal with it?
> > & thanks!
> > Gary
> > KA1J
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