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[TowerTalk] Terrain question

To: <>
Subject: [TowerTalk] Terrain question
From: (
Date: Sun, 19 Jul 1998 17:16:52 +0100

On Sun, 19 Jul 1998 07:45:16 +0100 Mike <> writes:
>Here is a good one for the masses.     
>I have to the north of me about 1.5 miles a hill of about 1100 feet 
>how is
>this going to effect radiation angle?
>We wont mention the 5000 foot mountains to the northeast and east of 
>me as
>they are much farther away.


The answer depends on several different factors, especially
the height of your antenna. You can download a copy of the
program TA from the ARRL server and run the numbers through it.

The answer is not as simple as finding the angle from your
antenna to the top of the hill, because the far-field pattern
is made up of the direct ray and the ray reflected from the
ground. The ray reflected from the ground will be cut off at
a much higher elevation angle, about 16 degrees. To some extent,
the answer also depends on the shape of the hill.

I have a hill to the east of me that actually HELPS me at low
angles by cutting off the out-of-phase ground reflection.

By the way, almost ALL of the propagation to Europe on 10/15/20
from W6 is at angles of 10 degrees or less. Statistical tables on
these propagation angles are included with the TA program.

Dave Hachadorian, K6LL
San Diego, CA

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