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Re: (meteorobs) Radio Observation of Meteors
At 12:04 AM 1999-08-21 -0700, you wrote:
>
> On the subject of radio observations, I was wondering if amateurs had
>tried radar detection of meteors themselves. Perhaps using a beacon
>with a directional antenna pointing upward, and a receiver with an
>upward facing antenna a few kilometres distant but out of the ground
>wave of the transmitter?
It's really not necessary to set up a bistatic (separate fixed locations
for transmitter and receiver) system. I won't get technical here on
MeteorObs but will say that it's quite easy for the ordinary amateur to
build an antenna switch using PIN diodes that will allow antenna switching
in plenty of time to receive echos from meteor scatter in a backscatter
system. The main problem will be having to design and build a receiver that
will recover quickly enough; but even that is not a major undertaking. In
fact, one Swedish ham, Leif Asbrink, SM5BSZ, has designed and built his own
system that he uses not only for meteor detection but also for detection
and evaluation of aurora conditions; see this URL, near the bottom of the
page:
http://ham.te.hik.se/homepage/sm5bsz/index.htm
I've built and tested my own PIN diode antenna switch which I've tested at
500 watts CW power, much more than sufficient, combined with a
moderate-sized yagi antenna, for detection of meteors, so can attest to the
practicality of this approach. I haven't had the time to complete a
receiver, however. But Asbrink also details a receiver system based on a
fast PC (Pentium II+ required) which can perform all kinds of data
processing including filtering of received signals, etc.
As for the type of modulation: software to generate phase-shifted audio
tones with which to drive a standard SSB VHF/UHF transmitter can be easily
generated using a PC equipped with a standard sound board. In point of
fact, computer-based high-speed morse code meteor scatter (HSMS) has been
growing amongst North American hams over the past three years, following
the popularity of that mode of communications in Europe for several
decades. We send and receive at speeds exceeding 3300 words per minute,
which allow us to have a signal transmitted that catch meteors providing
only a few milliseconds of reflection at 144, 222 or 432 MHz. The
very-high-speed morse code allows the exchange of copious amounts of
information even from sporadic meteors at any time of the day or night. The
one caveat is that to date, there are no beacon stations in North America
transmitting with high-speed CW (HSCW) although I believe there have been
plans for at least one such temporary manned beacon station located in the
Canadian maritime provinces during last year's Leonids shower. I haven't
heard of any such plans for 1999 Leonids as yet. The idea of the station
was to perform the first-ever cross-Atlantic meteor scatter contact between
North America and Europe using double-hop, or two simultaneous, Leonids
meteors which could extend the possible distance between the transmitter
and receiver stations to beyond 3000 km, spanning the Atlantic ocean.
I think the main key here is a lack of interest among the North American
amateurs in designing and building the necessary equipment. The costs of
the equipment would be nominal, comparable to ordinary V/UHF amateur
equipment already available. Due to the special fast-recovery requirements
of the receiver, however, a home-built receiver would probably prove as
easy to implement as modifying something bought off the shelf.
Clear skies,
SteveH
Amateur Radio Licensee K0XP
Central Massachusetts
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