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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