Re: (meteorobs) Radio Observation of Meteors
John Elder wrote:
> So, you add gain as you go up in frequency.
> Freq Ant Gain Echo Strength Sky Noise
> 28 0 dB 1.0 1
> 50 10 dB 0.5 1/10
> 144 15 dB 0.2 1/250
> It sound like you're getting the best SNR at 144 with your set-up!
Thanks for working out the figures John, it agrees with my experience.
I had much more luck on 144 MHz and the narrower beamwidth antenna than
I had on the lower frequencies.
> The reason I wanted to try WWV at 20 MHz is you get a 10 kW signal coming
> your way . . .
Unfortunately, coming my way, I think I'm well out of meteor scatter
range of Boulder, Colorado. Even the Canadian time station CHU (I think
its in the Ottawa area) on 14.670 MHz may be on the fringe of meteor
scatter range for me.
> > 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?
> Unfortunately, beacons are limited to 100 W. I'm not certain if that's peak
> or average power, though! if it's average, I'd love to run 10 kW peak at a
> 1% duty cycle . . .
I think it could be done with 100W or less. From St. Pierre et
Miquelon, just off the south coast of Newfoundland, on 144 MHz, I've
monitored a 20W beacon in NE New York state. If I wanted to listen for
meteors in a conic area overhead the round trip distance would be
between 300 and 400 km. With the receiving antenna directed vertically
I would hope to have reduced background terrestial noise.
To expand the idea, we use the same principles that are used in
aircraft radio altimeters, either wideband swept FM modulation or pulse
modulation, we may be able to actually measure the closest range of the
meteor. Compared to an aircraft radio altimeter we would have much
better receiver/transmitter isolation, higher transmitter power, larger
antennae (more gain), and operate on a longer wavelength (more reflected
signal) when compared to a radio altimter (4.2 to 4.4 GHz).
The system could be as simple as a single transmitter and receiver with
computer logging to sort out reflections from non-meteoric reflections
(overflying aircraft, etc.). Or I could envision a 5 station array, a
single beacon in the centre of an X and receivers N, E, S, and W of the
beacon. Meteors passing overhead the array that were detected by more
than one receiver, and if the time of the reflection was logged with
some precision, along with altitude, we may be able to roughly determine
velocity - its speed and direction.
OK, I'm inviting criticism, comments please!
Ron (in Gander)
College of the North Atlantic
Gander, NF, Canada
> Visit: http://www.jelder.com
> One does not become enlightened by imagining figures of light,
> but by making the darkness conscious.
> -- C. G. Jung
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