What about places where there is line of sight between the
transmitting antenna and the home antenna, but the home is a lot lower
or higher than than the T-antenna. Does the home antenna need to be
tipped up to point to a transmitting antenna that's higher? It sounds
like that follows from what was said ealier in this thread, but I've
never seeen it done or recommended.

You may get a slight increase in signal by uptilting the receive
antenna.

However, this is hard to predict, and usually not a terribly
significant factor, for two reasons:

(1) The amount of up-tilt you would need is not likely, in most cases,
to be more than a few degrees. It's probably less than the
"half-power vertical beam-width" of a typical TV antenna... likely
quite a lot less.

If, for example, the transmitting antenna is only 2 or 3 degrees
above the horizon, and the receiving antenna's vertical pattern
has a half-power beamwidth of 10 degrees or more (which would be
the case for all but the longest, highest-gain TV antennas), then
the amount of power you'd be giving up by not uptilting the
antenna is negligible.

(2) The signal path from the transmitter to your antenna is
complicated by reflections off of the ground, nearby buildings,
hills, and so forth. You might actually find a higher-quality
signal by pointing your antenna slightly away from the transmitter,
if by doing so you picked up a particularly strong reflection, or
_avoided_ picking up a side reflection which was causing multipath
distortion.

The cases in which an antenna needs to be pointed very exactly (both
horizontally and vertically), are those in which it has a very high
gain and thus a narrow beamwidth. How often will you be far enough
away from a transmitter that you need an antenna with this much gain,
*and* be so far below it that its position is a significant distance
above the horizon and would need to tilt it up by more than a few
degrees?

I don't think this combination of circumstances is at all common. If
it's close enough and high enough that it's far above the horizon,
then you're almost certainly able to use a low-gain antenna with a
very broad vertical pattern, and will get plenty of signal.

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