Joe Montierth wrote:
>Dean specified 100ft AAT, which takes into account the
>ground elevation, thats not very high off the ground.
>
>I own a 140 ft tower, with antennas that have
>relatively high gains. I can sit at the bottom of the
>tower (which should be the worst null) and still hear
>and get into the repeater. I can move .5 mile away
>with the same results. I can move 3 or 5 miles away
>with the same results.
>
>The null zones created by high gain antennas are
>usually so close to the antenna (when at 100 ft) that
>it makes no difference. By the time you get into the
>major lobe of the antenna, you will less than a mile
>or so away from the tower; as you get further away,
>you just get more and more into the beamwidth, not
>less. A high gain antenna may have a pattern that is 8
>degrees, that would be 4 degrees above the horizon,
>and 4 degrees below the horizon. With an antenna 100
>ft AAT, you would come into the major lobe just a
>little over a quarter mile from the antenna. I think
>most people would agree that if you're closer than .25
>miles to an antenna at 100 ft, you won't have a lot of
>problem hearing (or getting into) the attached
>repeater.
>
>I too, have worked in the RF field for a long time,
>and seen some strange stuff. One thing I consistantly
>see is that a high gain antenna will almost always
>outperform a lower gain antenna at the fringes, or
>near the horizon. It doesn't seem to matter if it is a
>100 ft tower, or a ten thousand foot mountain. Even on
>the 10,000 ft mountain it is hard to make the "nulls"
>of much consequence, since they are such an angle,
>reference the major lobe. This is from real-world
>experience also. Pehaps the laws of physics and
>trigonometry are different out east, I am only relying
>on "wild west" observations. :)
>Joe
>
>
Same stuff happens out here in the east. I have had the exact same
experience as suggested in the text above.
Kevin Custer
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