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[TowerTalk] Terrain question - takeoff angle

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Subject: [TowerTalk] Terrain question - takeoff angle
From: (Dale Jones K5MM)
Date: Sun, 19 Jul 1998 06:33:11 -0700 (PDT)

 One-and-one-half miles is about 7500 feet.  Use trigonometry and you will
 see that you have a triangle that is 7500 feet as the horizontal distance to
 the base of the hill, and the hill is then 1100 feet high.  Then:

 The tangent of Some Angle = 1100 / 7500 = 0.1467, Then the ArcTangeant
 of "0.1467" states that the angle is  8.35 Degrees.

 This states that your take-off angle from ground level at your house is about
 8.5 degrees.  If you are using high-gain 2 meter antennas for SSB scatter, that
 angle will be a BIG hindrance to you.  If you are using 3 element yagis for
 HF, not much of a problem.  

 In general that 8 degree angle to the top of the hill is NOT good news, but
 then it's not especially bad for HF either.  It would show up as being bad
 when you wanted to work Long Path in that direction, where you are looking
 for antenna take-off angles of 2 to 4 degrees.  

 You can use the same technique above to determine the take-off angle to 
 the larger mountains east and north-east of you.  Depends on how far
 away they are.

 73 & GL
 Dale  K5MM

At 07:45 AM 7/19/98 +0100, you wrote:
>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.

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