"zeno" wrote in message ...
Just in that last week I happened to notice two broadcasting antennas in
the
vacinity of where I live. In both cases it appears to be two towers about
100'+
tall which are about 100-200' apart. They are in a field with nothing else
around except a small building. I see no wire strung between the towers.
They
are guyed and the guys are broken up with insulators. Are both towers
driven or
is one a (parsisitic) relflector? Is this generally what AM broadcast
antennas
look like?

The usual practice is to drive both towers. Parasitic reflectors don't give
sharp nulls, and broadcast stations are usually "protecting" another
licensee on the same frequency, so the array will be designed to put a notch
in the signal toward the other "priviledged" station, while still assuring
the maximum possible coverage in the local area. That means driving both
towers.

The guys are broken with insulators in order to prevent the guy wires from
becoming parasitic elements, which could weaken the null(s).

This is generally what AM antennas look like if the station in question
wasn't licensed a long time back: some "clear channel" stations have
non-directional antennas, but that's rare, and some "sundowner" (i.e.,
daytime-only) stations are non-directional because they have low power and
aren't on at night.

HTH.

Bill