Dave,

Thank you once again.

You're most welcome. The real thanks go, of course, to the folks who
write those various wonderful educational pages. I've learned a very
great deal over the past year or so.

I'm going to run a maximum of 100W with my Icom 725 and assume (hope) that
the power level is low enough to avoid problems.

Ummph. You may have problems there.

Anecdotal evidence suggests that in a lot of residential situations,
running more than about 25 watts HF is fairly likely to create a
situation known as "fundamental overload" in nearby consumer-grade TV
tuners and FM radios. The strong RF signal saturates the tuner
electronics, forcing them into nonlinear behavior. It doesn't help
even if your RF signal is perfectly "clean" and has no harmonic
content (an impossible ideal) - even a pure signal will result in
these TVs and other such devices misbehaving (herringbone displays,
etc.).

Adding a high-pass filter at each affected TV set's RF input, and
adding choke filters to the power cord and A/V cables, can help a lot.

The same is true for telephones. I know that when I key up a 20-meter
PSK31 signal at about 20 watts, my wife can hear it on her telephone
(I really need to add some ferrites) and my antenna's outdoors up at
about 25'.

With an in-the-attic antenna you may need to keep power down to 5-10
watts to avoid interference.

That's the bad news. The good news is that cutting power from 100
watts to 10 is only 10 dB, which isn't even one S-unit on a typical
amateur receiver. Under most circumstances it won't make a big
difference in how audible your signal is. There's one particularly
skilled operator in my area who regularly breaks CW pileups to South
Pacific islands, running only a couple of watts, from an HF mobile rig
in his car. [Maybe if I play around with this stuff for a few decades
I might pick up a fraction of that skill... I should be so lucky!]

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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