On Sun, 25 Dec 2005 12:32:01 -0500, WA3GIN in Alex. City, VA
>I found the touch light control box inside the china cabinet.
>Is there a fix?
I assume that something is connected by wires. The wire(s) will
act as a an antenna, both receiving your transmitted RF and
radiating noise from the controller. (We call it a power cord, but
Mother Nature calls it an antenna). Both control wiring and power
wiring will act as an antenna, and depending on how they are
connected to the electronics, both can put RF into the
Ferrite chokes surrounding those wires can reduce the antenna
current. Look for ferrite parts that are just large enough in
diameter to surround the wires, and about an inch long. It may
take more than one part to provide enough impedance to reduce the
current enough to solve your problem. Put the chokes as close as
practical to the electronics.
Ferrites are made with a broad range of chemical compositions,
each with its own frequency range where it works best. Most clamp-
on ferrite parts that we see at hamfests are suitable for
suppressing 2 meters. If you're buying parts, look for Fair-Rite #
43 material, or Stewart #28.
RF is also coupled to the input terminals, and onto the circuit
board (the traces act as antennas too). RF bypass caps can help
this. You want small value caps with VERY short leads, and very
close to the junctions that are detecting the RFI.
There are tutorial app notes on my website about RFI and using
ferrites for suppression.
Jim Brown K9YC
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