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(meteorobs) Radio vs visuals
Notes are often seen in the literature about the number of visual vs. radio
meteors, what size particle is required for each, how the ionization
spreads, etc etc.
This came to mind as I was monitoring a schedule today on 144 MHz between
W5UN (EL29, near Dallas, TX) and W1REZ (FN55, Maine) from here in EM77,
central KY, right in line with them. That is a distance of over 1700 miles
- seemingly too far for either IOS (ionospheric scatter) or MS (meteor
scatter). But on Tuesday W1REZ heard W5UN several sequences, apparently
via IOS. On Wednesday, W1REZ received several pings. (Yes, they can
easily work via EME [earth-moon-earth, or moonbounce], but that wasn't the
intention).
Here in KY, as expected for the distance (790 mi/1271 km), it was difficult
to listen for ionospheric scatter because of the constant weak pings from
W5UN. All were short underdense pings - no overdense bursts. The number
varied from about 8 to over 20 per minute. (On W1REZ, 1020 miles/1641 km,
about 2 per minute). The ERP from W5UN's "Mighty Big Array" (see QST,
September 2000) is approximately 1.5 MW, which greatly helps with the
scattered signal from underdense trains.
However, a rate of 10 to 20 per minute is really not unusual (normal
morning sporadics). Several weeks ago I ran several schedules with N5BLZ
and N0KQY, hoping for some IOS. While both are large stations, neither are
in the same class as W5UN. But the distances were about the same (772 and
852 miles, optimum for me). And both averaged 10 to 20 (underdense) pings
per minute during several schedules. For these schedules, the pings, which
we normally utilize using high-speed CW meteor scatter, were again just in
the way, as we were attempting a contact by ionospheric scatter. As I am
in a small valley, I don't do well at long distances - those same days I
had a schedule with N1BUG in Maine, similarly equipped, and again averaged
about 2-4 pings per minute. (I seemingly have a "cutoff" distance at about
1250 miles because of the low hills here, and only once have completed a
contact by MS over 1400 miles).
During these several schedules, only 2 or 3 short overdense bursts were
heard. But the underdense pings were nearly continuous at times. (As an
aside - the number of pings on schedules like these usually does not
increase during a major shower. In fact, it usually decreases. But the
number of overdense bursts may increase greatly. While I have not run long
series of schedules with these particular stations, several years of
near-daily meteor-scatter schedules with 3 other large stations have born
this out).
What does all this have to do with visual observations? I really don't
have the foggiest idea. Except that forward-scatter radio observations and
visual observations are *so* different that comparisons too often are
meaningless.
For a little more, see the November 2000 QST or my Web site.
Keep them pings and bursts a-comin', folks!
Shelby, W8WN
Shelby Ennis, W8WN - EM77bq - KY
w8wn@arrldot net
w8wn@amsat.org
Web - http://www.qsldot net/w8wn/
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