[AMRadio] "Magic" lamp QRM

[Donald Chester]

I recently noticed a very rough, broad signal that wipes out 30-kc 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 kc 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
spectrum!

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 was probably the first time in over 20 years since anyone here 
brought home 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 
noise is far worse than the hash from my computer monitor, and I 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 because someone might be too lazy to flip a switch 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 swith with a knob 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 plate transformer and throwing the big switch.

Don K4KYV

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