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(meteorobs) Antenna headings
Several fellows have asked (direct, or on another reflector) about the
proper heading for a meteor shower if you have a directional antenna and
are using the FM broadcast band, low-VHF TV video carrier, etc.
General answer - This will not matter to most, who will be using
more-or-less non-directional antennas.
If you are using a directional antenna, the approximate rule is to simply
point at the station you're monitoring.
Technically, this isn't quite correct, but it's good enough for small
antennas. With a large antenna, the proper point is actually one of the
two "hot spots." But if your antenna is that large, you probably are
already familiar with this.
Note, however, that the *optimum* direction does vary constantly. This is
determined by the location of the radiant in the sky, and thus by the
geometry of the meteor trails in relation to the line between the
transmitter and receiver. This is of primary importance only for those
using meteor scatter for active communications. But for those using
signals in the lower VHF range (~30-150 MHz) to monitor a shower, and you
have only one station in a particular direction, you will note that the
maximum number of burns does not necessarily coincide with the peak of a
given shower. The highest rate may, instead, be at the time of maximum
"effectivity" for that direction.
It would be best if there were 4 or more stations on the same frequency,
400-1000 miles away, and at the 4 points on the compass. In some locations
this may be satisfied on certain frequencies on the FM band (or TV video
carriers). But too often there will also be a local station on the same
frequency which precludes use of the frequency you'd like to use.
Summary - in most cases, simply use a non-directional or low-gain
antenna. If you have a small directional antenna, point it in the
direction of the primary station you're monitoring.
IF you can rotate the antenna and wish to know more about the optimum
direction for a given time, MS-Soft, available free at
<http://www.sci.fi/~oh5iy/>, can figure this for you. This is a rather
complex DOS program, and uses the Maidenhead Square location system (but
you can use the mouse to click on an approximate location). Also available
at the same Web site are a group of HTML papers on the theory behind VHF
meteor scatter that are some of the best easily available on the subject,
which will explain all of the strange jargon used above.
If MS-Soft is too involved (but you should read the papers anyway, if you
are into using the radio), there is a simple DOS program about halfway down
the page at <http://www.qsl.net/w8wn/hscw/access.html>. It doesn't do
nearly as much as MS-Soft, but does figure the "effectivity."
Good monitoring! Hope our receivers are saturated!
Shelby Ennis, W8WN - EM77bq - KY
w8wn@arrl.net
w8wn@amsat.org
Web: http://www.qsl.net/w8wn/
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