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[Towertalk] 10M Takeoff Angles (Was: XR dilemma)

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Subject: [Towertalk] 10M Takeoff Angles (Was: XR dilemma)
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Date: Mon, 24 Jun 2002 06:43:30 -0600
Hi Mark,

I think our main disagreement comes over the the maximum
angle that is supported on 10M.  I believe that to be around
20 degrees (at very high MUF's).

Some time ago, someone plotted his 10M SS contacts on
a map.  The vast majority were at skip distances of 900 miles
or more, which corresponds to takeoff angles of 20 degrees
and BELOW.

At 18 ft, a 3L 10M Yagi has the majority of it's radiation between
20 and 30 degrees.  3 dB points are 15 and 40 degrees.  Over
80% of the energy is above 20 degrees, i.e. going into outer space.

At 35 ft, the 3 dB points are 7 and 22 degrees with the vast
majority of the energy falling in the range of angles supported
by the ionosphere.  I see NO BENEFIT in going lower than
35 ft  on 10M.

Tom  N4KG

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