[RFI] Noise DR
EDWARDS, EDDIE J
EDWARDS, EDDIE J" <email@example.com
Fri, 19 Nov 1999 17:00:48 -0600
> -----Original Message-----
> From: kmarch [SMTP:firstname.lastname@example.org]
> I've reached the point with neighbors noise where I have to build a noise
> direction finding antenna. The intent is to walk around the local area
> carrying a DR set up to find out from which residence the noise that is
> QRMing me originates. Before I knock on a door I wnat to be certain I
> have the right place so I don't waste a silver bullet. This is primarily
> low band stuff 160 and 80 M. It sounds like one of these new SCR
> controlled lamps that spits out junk several mhZ wide and varing in freq
> peak and intensity. Doesn't show up much on higher frequencies. Can
> someone recommend a DR device that will give me enough ability to track
> down noise? Is a ferrite rod set-up sensitive enough or is a loop better
> for detecting small noises? Pre-amps required? Ideas? Bob
[Ed-K0iL] First off, What is DR? Typo? Do you mean DF for
You seem to be heading down the right path. Although I don't think
it's a touch controlled lamp based on your description and my experience
with several of these type of lamps. At least the ones "MADE IN TAIWAN"
that are not UL listed.
TC lamps will have repeating buzzing signals approx. 40-60 Khz wide
and repeating every 150-175 Khz. Very quantized. Freqs in between signals
are totally quiet (at least from the lamps). It also has "peaks" on the
edges of the 40-60khz pulses. You ought to see these things on a spectrum
analyzer! This won't do it justice, but here goes:
Use Courier to view:
/ \ / \
/ \____________/ \
If it doesn't look like this, it probably is a TC lamp.
The band(s) affected depend on the household wiring and where the
lamp is plugged into the house. The ones I've found nearby always seem to
get 20 meters the worst and 15 kinda bad. So I tracked them on freqs just
above 20 meters.
If it is a TC lamp here's some hints from an experienced TC lamp
tracker. Found three noisy ones and one Not noisy! The Not noisy one found
me. Awhile back, a neighbor asked if I was on my ham radio the other night
at 1 AM. I said I was. They said their lamp was going on and off until
they unplugged it. Simple ferrite stopped that.
All I've ever used to track touch lamps is a portable short-wave
rcvr. The smallest Sony unit works real well. Get a unit that can analog
tune not a digital one that jumps 5 khz.
First find the strongest noise from the ham shack. Tune the
portable to that freq and go for a walk! As you get close (noise gets
louder/stronger) fold in the antenna and use your hands and body to
attenuate the reception. Go past the strongest noise area and come back.
Do this several times. Probably best to do this in daylight so nobody gets
too nervous watching you walk back and forth and at 90degress (cross the
street) also if possible.
Once you've figured out which house or pair of houses, consider your
next step carefully. This is were it takes every ounce of PR and
neighborliness you can muster. If no one is home, I've found leaving a note
does work if the note is friendly and asking for their help to figure out
your problem. Everyone wants to be a good neighbor and help if possible.
If they are home apply the same friendly "can you help me?" approach
face-to-face. Don't make threats that you cannot back up, like the FCC will
get ya; They won't! I tried the "it must be malfunctioning and could be a
fire hazard", but I could tell right away it had no effect.
The best approach is "let's see if we can fix this lamp so it
doesn't do this anymore". In one case I asked if I could take the lamp in
to an electrician and have it repaired. I then took the lamp and bought and
installed (myself) a new controller that was a little quieter and added
filtering differential and common mode per the ARRL RFI Handbook and QST
hints & kinks articles. Reduced the noise to an acceptable level. It takes
a lot of cooperation from the owner; just remember, they don't have to do
anything for you unless they want to.
de ed -K0iL
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