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Re: (meteorobs) Radio Observation of Meteors

From: Ron Thompson <rlthompson@thezonedot net>


>meteor scatter does not
>work well on the HF bands.  For the most part it is a VHF phenomenon, up
>into the UHF range.  As I understand it, the meteor scatter automated
>counting networks are using 24 hr broadcasts from 'low VHF' TV stations,
>and FM broadcast stations for the most part.  Along with a computer and
>software to count the relections.  I believe, and stand to be corrected,
>that the ionization trail of the meteor reflects the shorter wavelength
>VHF signals much better than HF.


Actually, HF signals reflect just fine off meteor trails. But, HF signals
reflect even better off the ionosphere. Makes the meteor echos much harder
to count. I believe that the optimum meteor radar frequency is around 30
MHz. 20 MHz WWV is a bit lower than that, but in the absence of skywave, it
should make an excellent beacon for meteor work.

I'm not a physicist, but my boss tells me that the strength of a meteor
trail echo is proportional to the electron-density-gradient divided by
radar-wavelength. My brief experience with meteors at different frequencies
is as follows:

~3 MHz, 100's of kW, Alaska and Puerto Rico. Echos that typically last for a
"long" time (I'd have to go back and sort through our data to tell you what
long means. Probably several seconds). [Ionospheric heating facilities
operating as pulsed HF radars]

49.92 MHz, 25 kW, Puerto Rico. Most echos are brief, less than a second.
Some are much longer [Meteor radar]

138.8 MHz, 35 kW, Virginia. Meteors were noise & we filtered them out.
Noticed them on a scope as brief deflections.

224 MHz, Tromso Norway, 100's of kW. Very brief--lasted only a few
milleseconds.

430 MHz, Puerto Rico, 400 kW. Our pulse period was 10-60 ms, but we never
saw a meteor in two consecutive pulses.

900 MHz, 100's of kW, Tromso, Norway. Brief, single pulse echos.

(If somebody out there has a hankering to analyze meteor data tapes, let me
know . . . we have gigabytes of data where meteors were of no interest to
us, but we recorded them anyhow!)

> A websearch should turn up the websites for the Society for Amateur
>Radio Astronomers, and others, who have members who do automated meteor
>counts via radio.

Thanks, I'll take a look at these.


Regards,

John Elder
KO6X
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