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Topband: "Magic" lamp QRM

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Subject: Topband: "Magic" lamp QRM
From: (Donald Chester)
Date: Sat, 05 Oct 2002 21:44:43 +0000
I recently noticed a very rough, broad signal that wipes out 30-kHz portions 
of the spectrum from the middle of the broadcast
band through 10 m. It is especially bad on 160 and 80m. I did a little 
sniffing with a portable radio and found the source to be a
table lamp my daughter just bought. The thing doesn't have a conventional 
switch, but a metal base, and you turn in on and off
by touching the base with your hand. The thing must have some sort of 
oscillator somewhere in the 450 kHz range, and works by
detuning the oscillator when you touch it. What kind of rubbish is someone 
going to think of next to garbage up the radio

I have never seen one of these things before. Is this a novelty or 
speciality item, or is this the way all table lamps are made these
days? (This is probably the first time in 20 years since anyone living here 
bought a new table lamp.) Surely, this must fall under Part 15, so I wonder 
why the FCC even allows those things to be sold on the market. The QRM is 
far worse than the hash from my computer monitor, and I had thought that was 
already bad enough. I'm surprised the AM broadcast industry isn't raising 
bloody hell about stuff like this. I can't imagine polluting the rf spectrum 
with rubbish just because someone might be too lazy to flip a switch to turn 
on a table lamp.

I'm wondering if anyone else has had problems with interference from those 
things, and what might be the simplest solution. I tried an in-line rf 
filter, but it made no improvement whatever. Unless there is something 
simple to by-pass, the only solution I can think of is to go into the thing, 
rip out the electronics, and mount a conventional switch on the base. I'd 
like to hear form anyone who has successfully fixed one of these things some 
way other than clip-leading the power cord across the HV terminals of the 
final amplifier plate transformer and throwing the big switch.


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