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(meteorobs) Radio Meteors
The following data applies to the radio detection of Leonid meteors. Note
that data for visual observation should only be used as a rough guideline
since radio detection and visual detection will peak at different times.
This occurs because visual observation is a 2-point system, i.e. only the
meteor (source of light energy) and the observer are involved. Radio
detection is a 3-point system, i.e. the source of energy is a radio
transmitter, the meteor (ionized trail) is merely a 'reflector,' and then
there is the observer. The geometry involved in radio detection is
therefore more complex than that in visual detection. Consequently, meteor
position is more critical in radio detection than it is in visual
detection.
The data below indicates which direction to point a beam antenna (yagi, tv
antenna, etc.). If you use a dipole, it should be strung perpendicular to
the directions given below. For example, if the best signals come from the
North, then a beam antenna should be pointed North, but a dipole should be
strung East-West.
Data shows the best times and directions for longitudes of 60, 75, 90, 105
and 120 deg. In North America, latitude will change the times only
slightly. Since you should accept the times for what they are (mathematical
calulations which are not necessarily extremely precise), the variation due
to latitude becomes insignificant. Having said that the calculations are
not extremely precise, you should listen several hours before and after the
times listed to ensure that you don't miss the peak.
To accomplish this (and avoid losing too much sleep or work time) you might
try feeding the audio output from your receiver into the audio input of a
VCR. This will give you 6 hours of tape. You can playback the tape through
your tv set later. If you set the VCR timer for 3 hours before the times
indicated below (in which case the tape will run until 3 hours after the
times indicated), this should increase your chances of success.
Also note that I have given times for North, South, Northeast and Northwest
propagation. Since 'reflection' from meteors should be symmetrical, this
would indicate that reception from the Southwest and Southeast should be
possible. In fact, this should be true, however, Northeast and Northwest
are better bets for Leonids. That doesn't mean you should not give
Southwest and Southeast a try. As you will figure out when you see the
data, the times for North and South propagation are the same; therefore you
can use the data for Northeast propagation if you want to listen for
signals from the Southwest and data for Northwest propagation if you want
to listen for signals from the Southeast.
I calculated times for 45 deg North and also 30 deg North. At 30 deg North,
most propagation is North-South, there is less of a chance for hearing
signals from other directions than there is at 45 deg North. Again, that
should not stop you trying other directions if you live in the south.
One last point--the times below are peak times. Signals will be heard
before and after these times.
The data was derived from a program written by Michael Owen, W9IP. All
times are UTC.
Receiving site location: 60 deg W
Direction and times to listen--
North: 0700 and 1345 UTC
Northeast: 0730
South: 0700 and 1400
Northwest: 1300
Receiving site location: 75 deg W
Direction and times to listen--
N: 0800 and 1500
NE: 0830
S: 0800 and 1445
NW: 1400
Receiving site location: 90 deg W
Direction and times to listen--
N: 0900 and 1600
NE: 0930
S: 0900 and 1545
NW: 1500
Receiving site location: 105 deg W
Direction and times to listen--
N: 1000 and 1700
NE: 1030
S: 1000 and 1645
NW: 1600
Receiving site location: 120 deg W
Direction and times to listen--
N: 1100 and 1800
NE: 1130
S: 1100 and 1800
NW: 1700
For further background information--Sky & Telescope, December 1997, p. 108;
Observer's Handbook (Royal Astronomical Society of Canada), 1998 edition,
p. 183 or 1999 edition, p.205; or
http://www.durhamradiodot ca/odxa/meteors.html
Philip Gebhardt, VE3ACK
pgebhardt@compuserve.com
Greenbank, Ontario, Canada
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