"Sal M. Onella" wrote in message
news:w3DYg.5744$gM1.5721@fed1read12...

"CW" wrote in message
ups.com...
Fellows,

I've been wondering for some time now why amateur operators don't build
their Yagi antenna's
so they can be raised and lowered about 10ft in addition to being
rotated.
It seems to me that raising and lowering the height of a Yagi affects
the take-off angle by at least several degrees, meaning that the signal
delivery (target area) would be moved by at least many hundreds of
miles.

I don't know if this helps, but advice for TV DX says that you get
progressively improved performance until the yagi's
height-above-average-terrain (HAAT) is equal to about ten wavelengths.
(Above that HAAT, the signal strength varies up and down with further
increases in the elevation )

I never tested the idea, but if correct and it also holds for HF, there
won't ever be anybody _lowering_ a HF yagi. We would want the most
height.
At the 2006 Field Day, one team had multi-band beam at 85 feet and
everybody
loved it.

no, it doesn't hold for hf. tv dx is basically a line of sight vhf/uhf type
of propagation where height is everything. the higher you can go the
better, i don't know where 10 wavelengths came from since that is actually
pretty low on the higher uhf channels! on hf you can't get high enough to
get away from the ground reflection effects so you might as well put them to
good use. And yes, when bands like 10/15/20m are wide open from new england
to europe the best antennas are often the lowest ones here... i.e. my yagi
at 30' on 10m will have much stronger signals than the ones at 60, 90, or
120'. and yet at other times, like now, on 10m my yagi at 180' is often the
only one to hear any dx.

so the answer is: yes, you can be too high, but no, you can't get too high.