[Antennas] Using GeoClock To Find True North

Mon, 18 Feb 2002 14:34:21 -0500

A similar discussion here awhile back led me to add the requisite
capabilities to DXView -- it lets you know when the Sun's longitude is
identical to yours so you can run out and check your antenna. And when you
discover that its not perfect, you can set an offset so that DXView
precisely aims your array. Yes, its understood that aiming an HF array isn't
that critical, but VHF and UHF arrays have narrower beam-widths, and besides
its nice to have it "right".

DXView is available via www.qsl.net/dxview ; like all DXLab applications,
its free.

   73,

       Dave, AA6YQ

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Merv Stump
Sent: Monday, February 18, 2002 12:39 PM
To: [email protected]
Subject: [Antennas] Using GeoClock To Find True North

The ARRL Antenna Book describes a method for finding true north based on the
fact that the sun is directly south at 12:00 noon local time.  This is of
course only true if your qth is exactly on the longitudinal meridian on
which your time zone is based (e.g. 75 degrees for EST); and on the dates of
the summer and winter solstice.  For any other location and on any other
dates, corrections have to be applied to determine the exact time at which
the sun is in the south.  The antenna book explains how to make these
corrections.  However, I just noticed that GeoClock gives you the azimuth
and elevation angles for the sun at all times.  When the azimuth angle is
180 degrees, the sun is in the south.  Today at 12:08:40 I ran to see if my
boom lined up with the shadow of my tower.  It's a little off, and now I'll
have to worry about it until spring.

Regards, Merv

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