thanks for all the good info on a subject I'm just starting to learn


"Al Klein" wrote in message
...
On Mon, 23 Oct 2006 01:20:04 -0500, "TongSlinger"
wrote:

I have another question if I put the antenna half way up the tower will I
have decreased signal coming into the antenna through the triangular
tower.
would this not let the antenna be truly Omni? my tower is about 75 feet
tall
and I do not have access to the top of the tower?

Depending on the distance between the tower and the antenna, and the
frequency, you'll have a directional antenna pointing somewhere -
either away from the tower, side-to-side relative to a line between
the antenna and tower or somewhere between the two. You'd have to
mount the antenna at least 3 or 4 wavelengths at the lowest frequency
you're interested in (which would be around 25 feet at 150 MHZ,
further for aircraft or VHF-lo) - 6 to 10 wavelengths is better - to
get back a somewhat circular pattern.

Since you'll be using the antenna at widely different frequencies
there's no one solution unless the transmitters you want to monitor
just happen to all be exactly where the antenna pattern points for
that frequency. If you're that lucky, buy all the lottery tickets you
can find - they'll all be winners.