For those concerned with determining the magnetic declination (or variation)
for your QTH, be advised that the figure shown on your local USGS topo quad
map may be over 25 years out of date. The magnetic declination does change,
albeit slowly, with time. Even the FAA sectional aeronautical charts at
times display figures up to 6 years out of date.
Try this online calculator, courtesy of NOAA, U.S. Dept. of Commerce*:
http://www.ngdc.noaa.gov/cgi-bin/seg/gmag/fldsnth1.pl
It is educational, even if you do not need the precision offered, which
indeed you don't for HF work. This seems to be based upon the same
mathematical model that is used for generating the values on the government
maps.
*I am not affiliated with the U.S. Gov't. nor do I stand to profit from any
association with it (ha).
73,
Charley, K7NW
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