"Bob Haberkost" wrote in message
...

But....I've seen (and fortunately NOT had to deal with) antenna systems
with very
high base impedances (one, if my memory serves me correctly, was 800 ohms!
Not much
current, but do the math...any appreciable power, like 3 or 4 kW, and
there's a real
danger of getting tangled in with some pretty high voltages). While it's
not a
scientific survey, I can tell you that those systems, watt-for-watt,
perform worse
than lower impedance systems, and that's not even counting the
difficulties in having
1kV base voltages!

At medium wave (AM Broadcast) many Class A stations (formerly "clear
channel") use antennas of about 190 or 200 degrees tall. The FCC requires a
minimum antenna effectiveness for that class which is higher than for the
other classes of stations. The base impedance of these sticks near a
half-wave tall is going to be pretty high - and all but one US Class A
station run 50 kW. One of the factors in deciding AM tower height is to
place the first null in the vertical pattern such that the nighttime skywave
interferes as little as possible with the ground wave toward the edges of
the groundwave coverage.

Of course Class A AM stations are a Big Deal and generally have very good
ground systems.