"New Question" wrote in message
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"dicko" wrote in message
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If you go to www.antennaweb.org, it will give you compass bearings for
all the stations you can receive. Then it's a simple matter of getting
up on the roof with a compass and accurately pointing the antenna per
the compass.
Where can I purchase an inexpensive compass for doing this?
The compasses I've seen on the internet appear to indicate the following:
South: 0 degrees
West: 90 degrees
North: 180 degrees
East: 270 degrees
This is opposite to what it should be. A heading of North is 360 degrees,
South is 180 degrees, East is 090 degrees and West is 270 degrees.
Is it possible to just look at my approximate location on a map and
estimate
the correct direction to point the antenna in, based upon the direction of
the particular stations the I use the most?
Keep in mind, the directions given on the
www.antennaweb.org website are
based on *magnetic* north, not true north. It assumes that you will be
using a magnetic compass to point your antenna.
If you use a map to determine relative direction to the station, it will be
based on *true* north, not magnetic north. Depending on where you live,
there can be as much as 20 degrees difference between true and magnetic
north. If you figure the direction to the station on the map, and then use
the compass on the roof to figure relative direction based on what you came
up with on the map, you could be as much as 20 degrees off (depending on
where in the USA you live). This is because the geographic poles and the
magnetic poles are not collocated. Plus, stray magnetic fields in the earth
introduce some error as well. It's called magnetic variation. It's easy to
compensate for if you know what the variation is in your particular
geographic area. For example, if the magnetic variation is roughly 15
degrees east, and you calculate the relative direction to the station on the
map as due West (270 degrees), you would need to subtract 15 degrees from
your compass reading and point the antenna to 255 degrees magnetic.