[TowerTalk] True, True North

[Roger L. Elowitz]

Hi  Paul, WA6IBU, and the TowerTalk gang who were waiting for this.....

Paul's last post seems that he has a good handle on the subject.

I swore I'd keep out of this but the issue cries out for a little
clarification and attention... or perhaps it's only me crying out for
attention. (Probably the latter).

The north magnetic pole is located under water in Canada's Parry
Channel on
the 102 degree West line of longitude at about the level of the 80-degree
line of North latitude... according to my very old atlas. (It's probably
changed position since this book was published!)  If you were to draw a
line from the True North Pole on down through the Magnetic North Pole and
continue on down.... you would have a line called the Agonic magnetic
line.
Should you be located anywhere on this line your compass would point to
the
True North Pole.  

Unfortunately, everything isn't that simple.  As you follow that line down
towards the equator.... local deposits of ferrous minerals "pull" that
line
one way or another (east or west) slightly...  stating this point for the
benefit of the purists and WWII navigators (Stu, WA2MOE) who are reading
this.... so the Agonic line isn't all that straight.

Facing "North," if you are to the left of the Agonic line..... your
compass
would always point somewhat "east" of True North.... and if you were to
the
right of the Agonic line your compass would always point "west" of True
North. To correct for these errors and determine "True" directions with a
magnetic instrument, you must follow the rule all novice pilots and
navigators have forever committed to memory.... "Easterly variation is
Least and Westerly variation is Best."  With that nonsense said... you
must
then relate "Least" with "Subtract" and "Best" with "ADD." 

In other words.... if you are to the left of the Agonic line (facing
north)
.... such as you are in San Francisco... your compass is pointing to the
East of True North requiring you to subtract the difference in the
readings
(the local variation) to go from compass reading to True North. The advice
you were given by Pat Barthelow,  AA6EG is absolutely correct. Assuming
your local magnetic variation is 14-degrees.... (any Sectional aeronatical
chart of your area will confirm it),  putting the 14-degree marking under
your compass needle will result in the compass card's North indicator line
correctly pointing to True North. 

Also, at the risk of being repetitious... it is very true that most
amateur
beams are so broad that a fifteen degree error may not be noticeable.  I
say, if you're going to the trouble of turning that monster of an antenna
in that beautiful tower you spent a fortune on in time and labor...
getting
your beam pointed correctly is just the last thing you want to do
correctly... IMHO.  What the hell... you've done everything else "by the
book"...what's wrong with a little purist's fun in the search for
accuracy?
If it makes you happy... go for it!!!

Will the wind eventually twist the antenna from it's correct setting? 
Perhaps!  So you will have yet another excuse to climb the tower and check
things anyway.... in the interest in preventive maintainance and safety. 
Will any errors in the heading reading affect you contest scores.... we
all
seriously doubt it.

Hey... it's cool to be able to type a dx call into your logging
program....
have the guy's name and qth pop up on the screen along with his distance
and bearing to your station and then have your control box automatically
bring your beam to that heading.  Most of us can only dream of doing stuff
like that... not because it makes one iota of difference in getting the
contact or not.... but simply because... it's "cool to do" and Hey!!!....
that's the way us control freaks choose to play this game.  It's just
another button to push and another knob to tweak and that's what gives us
pleasure.

'Nuff said.  Now go out and have fun... all the while remembering those
imortal words of the prophet.... "he who dies tweaking the most toys...
WINS!"

73,

Roger, K2JAS

PS Thanks to Stu, WA2MOE for his input on my prolix output and to Dick
Bodine, WJ0M for remembering the "good times."









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