Ed,
Thanks for lending your expertise to this problem. Others have
mentioned PC monitor or switching power supply noise. In my case
the noise is present 24 hrs a day. You say that the touch lamp
is typically 30-70 khz wide. In my case it is no more that 5 khz
wide. I don't have a scope handy so I can't say what the envelope
looks like.
One question, though. How were you able to track down the touch
lamps over a block away?
Thanks again,
Kris N5KM
Ed - K0iL wrote:
>
> Kris,
> My comments are below:
>
> On Saturday, 23 December, 2000 8:47 PM, Kris Mraz N5KM
> [SMTP:kilo.mike@gte.net] wrote:
> > I'm being plagued by a noise on the 80m band.
> > The noise is a raspy buzz that starts at the low end of 80m and
> > repeats every 67 khz up past 4000 khz. I've recently put up a
> > 4-square antenna and I can peak the noise in one direction. Could
> > this be
> > 1. a touch lamp?
>
> This is my bet based on your description. I've tracked down almost half a
> dozen in last 10 years. It's probably one of the inexpensive "Made in
> Taiwan" models that are NOT UL listed and do not meet Part 15 specs at all.
> These generally have a bandwidth of anywhere from 30 to 70 Khz width, and
> a repeatitive frequency around 70 Khz +/-5 Khz. They have free running
> oscillators in them that couple to the house's AC wiring and find
> resonances in the wiring that amplify the noise on certain bands while on
> other bands it's clear or weak. If you plug them into different circuits
> in the house, they'll change what band they resonate on, or sometimes the
> noise goes away comepletely if there is no resonance found.
>
> One very distinctive feature of touch lamp noise on a scope (you can see it
> on an S-meter as well) is a higher than average peak at each end of the
> noise bandwidth sort of like this (format for porportional font like
> courier):
> __ __
> / \____________/ \
> / \
> / \
> __/ \___
>
> The noise is quite distinctive on a spectrum scope like on the Icom 756.
> You can see the individual pulses moving across the bandwidth.
>
> > 2. an SCR dimmer?
>
> Could be. Maybe. These are similar to touch lamps.
>
> > 3. a wireless modem?
>
> I don't have any experience tracking any of these down...yet!
>
> > Note, I'm currently hearing multiple wireless modem buzzes/
> > carriers between 3514 an 3550 Khz. Have any of the above listed
> > possibilities been known to have harmonics every 67 khz?
>
> Yes, touch controlled lamps as I mentioned already.
>
> > I know
> > the wireless modems have quite a range. How far can the other two
> > devices radiate?
>
> I've tracked down touch lamps over a block away. Found two in a house
> across the street from the house behind me. Found another in a house on
> the block corner opposite my location.
>
> When they are close enough to you like next door, you can control them with
> your radio transmissions. Years ago, a new neighbor moved in directly in
> back of my house. I was sitting in front of the HF rig listening when they
> plugged in their touch lamp. 10-20db over S9 of noise pulse every 72 Khz
> across the band popped up immediately. I QSYed to CW and tuned to the
> bottom of a pulse. When I keyed the rig, the pulse shifted upward a few
> KC. Retuned to the bottom & keyed and it shifted it again. Same thing the
> third time. On the fourth key up, it shifted back down to abt the original
> starting freq. I had total control on the 3-way lamp! >;^}
>
> So I went abt having some fun with it. I sent messages encoded by the
> number of shifts. Not sure if they ever copied the messages, but they sure
> unplugged the lamp everytime I played with it very long. They either
> thought it was broken or that their new house was haunted!
>
> Latter that summer I saw they had a garage sale. Stopped in and found they
> had a touch lamp for sale. I probably should've bought it to ensure no one
> nearby did, but apparently no one did since it hasn't shown up on the bands
> for years now.
>
> 73,
> de ed -K0iL
>
> Here's some RFI archives on the subject:
> http://lists.contesting.com/_rfi/199904/0004.html
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