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[TowerTalk] Let's deviate

To: <>
Subject: [TowerTalk] Let's deviate
From: (Stu Greene)
Date: Sat, 22 Sep 2001 15:51:42 -0700
At 10:22 PM 9/22/01 +0000, John Farber wrote:

>Magnetic declination is not the same thing as magnetic deviation. I think
>you guys are talking about deviation from true North, whereas mag
>declination is the vertical angle the field lines make going into the Earth,
>and that varies by latitude.

Declination, not magnetic declination,  is the bearing of a celestial body 
from the observer. When coupled with elevation, a line of position can be 
obtained,  Cross two or better three,  lines of position and you have a 
geographic location or "fix". Talk to a navigator and you will understand.

  True heading, plus or minus variation, is called magnetic heading, ie the 
direction or bearing to the magnetic north pole. Add or subtract compass 
error (deviation) and you have compass heading.

Variation in most parts of the world can be obtained by calling a local 
airport, or, if you prefer, doing a search on the Web.  Deviation of a 
cheap Boy Scout compass is not worth calculating, but if you have a 
sophisticated large bucket compass deviation can be calculated by using an 
astrocompass which shows true heading.  After adding or subtracting 
variation you look at the compass and the difference is deviation  Most 
people who use large compasses (flyers, mariners) swing them every 15 
degrees of bearing beginning at North.  It takes quite a while..

   If you point an antenna at a bearing where the signal is loudest you 
have it made.  A guess at True North is good enough and while this subject 
recurs like the seven year itch,  your antenna is OK if you use the shadow 
method (bulky) or Polaris (easy)

Now,  how many owls can be positioned on a non-polished element for maximum 
gain and  front to back?

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