On Fri, 22 Oct 2004 09:07:53 -0700 (PDT), Martin Ewing wrote:
>That's not intended to be snide, elitist, or
>anti-elitist. But the hypothesis is that going from
>100W to 1 kW can cause a lot more than 10 dB increase
>in RFI.
Two things at play. First, virtually all detection is square law, so once
you above a threshold where detection takes place, a 6 dB increase
in power will cause a 12 dB increase in the strength of the detected
signal.
Second, some detection takes place only above some threshold
(fundamental overload, for example). As long as you are below that
threshold, no detection takes place.
For all of my ham career until about three months ago, I've been a
"100 watts to a dipole" guy. I run antennas that are within a few yards
of home audio gear, TV sets running from antennas, and even within a
few feet of those antennas. The electronics equipment in my home
ranges from pro quality audio gear to low grade consumer gear for
video, computers, microwave oven, telephones, etc. Some of this
gear (but not much of it) needed ferrite chokes to prevent problems at
100 watts on a few bands (especially 6 meters). Most of it did not.
I recently bought a Titan amp (1500 w rated) and am running it at
around 1 kW out. When I did that, I needed to add chokes to
loudspeaker wiring, telephone wiring, and in some cases line level
wiring of some home equipment. I also needed to filter the power line
to prevent GFCI outlets from tripping, and I had to filter a doorbell line
to prevent the Sonalert that was connected to it from rectifying the
transmitted signal. I also added professional quality bandpass filters
to the antenna distribution for FM and TV antennas, and I have added
ferrite chokes to coax at selected points. I still have a few problems
on a few antenna/band combinations, but for the most part, I can run
full power without giving the XYL problems! And remember, this is
with antennas that are within a few yards of the equipment!
Jim Brown K9YC
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