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Fwd: [Radio-Astronomy] Question about radio detection of Leonids



I recieved the following from the radio-astronomy mailing list and thought it
might answer some of the questions I've seen regarding radio and the Leonids.
Hope you'll find it useful.
Raymond Remmel
AC5QV




Hi Ron, Vince and list,

Thanks for your quick and extensive info on meteor monitoring. I have
a Realistic Pro-2035 in the shack, it has 50 - 60 MHz capability and I
think I'll connect it to a nice dipole this weekend :) I haven't used
it much on 6 meters yet.

In the meantime, a friend of mine sent me a message concerning ELF
monitoring, posted on a meteor watchers' mailing list some time ago.

Here are some interesting excerpts :
=======================================

Yes they [meteors - Frits] produce radio waves. They produce
electromagnetic waves in the VLF and ELF (very and extremely low
frequency) range around 10 to 60 Hz (that's Hz not KHz). This low
frequency radio energy has been known to induce vibrations in metal
objects (like your glasses frames) producing sound waves (very rare).
It takes a very large meteor to produce a recordable event but the
effect is very common and well recorded during space shuttle
reentries. Every space shuttle reentry produces an easy to record
event. Sky and Telescope and Scientific American have both run artcles
with instructions on how to receive the signals. The easiest way is to
simply take a very long wire 10ft or more, and connect it directly to
the microphone jack of a tape recorder. No radio receiver is required.
Some people use large ferrite bar antennas with long wire wraps but
that can overload a microphone input. Then later play the tape into
your computer via the sound board and keep it as a WAV file, then
analyze the wav file with a sound editing program like Cooledit (there
are lots of freeware sound programs out there). Cooledit will do a FFT
(fast fournier transform, hope I spelled that right) and you have the
frequency of the transmission... easy. You could set up a wire and
tape recorder during a meteor shower and if you see a REALLY big one
mark the time and input it into your computer later.
Dale

Another posting:

The best article I have seen is in the December 1985 issue of Sky and
Telescope magazine pgs 623-625. It has a good discussion of the mechanism
of radio energy formation by the meteor plasma trail and info on building a
receiving device as I described. It refers mostly to VLF 1-10Khz but ELF
down to 1-60Hz has also been detected.
Another source is Scientific American May 1996 and Nature vol 254 Apr 3 1975.
While the recording of the radio noise is rather simple the mechanism of
audible sound production is still debated.
Dale

At 12:14 PM 8/13/98 -0400, you wrote:

Thanks for jumping in on that one, Dale. And glad to final hear of definite
confirmation of the electrophonic effect! I've observed it twice myself, and
have heard many observers mention it. But there are a few folks,
including some quite prominent on our list, who have NOT observed it
themselves and therefore dismissed it as a "psychological effect".

BTW, I was amazed to hear that the detection of VLF from meteors was
so simple! What other data about the meteor can amateurs derive from
this setup, besides just the frequency of emission?

Clear skies,
Lew


Dale Ireland  47.7N 122.7W
Astronomy Page http://www.drdale.com
Comets, Eclipses, Photography, Fabrications
===============================================

On 1998-11-13 Dunbar.Ron@oscsystems.com said:
   >Frits,
   >The easiest (and probably best) way to 'see' meteor activity is by
   >monitoring a VHF TV Channel's video carrier ... this has been done
   >by many, many amateurs for many, many years!  In the U.S., TV
   >channel 2 (video carrier = 55.250 MHz, +/- 10Khz) and Channel 3
   >(video carrier = 61.250 MHz, +/- 10KHz) are the most popular.  The
   >FCC assigns the 'offset' of 0, +10 or -10KHz to minimize
   >herringbone interference between stations that might interfere with
   >each other during enhanced propagation conditions.
   >I use an old 6 Meter converter which has been modified to tune to
   >55.250 MHz feeding into a receiver capable of CW or SSB operation.
   >You will want to select the channel that you do *not* have locally,
   >since a local will overload your converter and receiver and make it
   >useless for listening to 'DX'.  Not only will you hear many pings
   >(some as much as 20 - 30 seconds long, others only 300mS in
   >duration), but you'll easily be able to tell when other propagation
   >enhancement is occurring, such as Aurora (you will hear the
   >relatively pure carrier change to a loud raucous whisper, then a
   >roar as the aurora gets going), Sporadic E and Tropo ... after a
   >few weeks of monitoring, you will develop a 'feel' for what the
   >'normal' background level of the offset you choose to monitor ...
   >remember, because there actually are stations on all 3 offsets,
   >with your single converter, you actually get a coice of 3 carriers
   >to listen to.  In addition, there are (of course) many more
   >stations actually residing on those 3 offsets, but you will not
   >normally hear them ... that is, UNTIL a huge long-burning meteor
   >reflects the signals of more than one station as it passes through
   >the proper positions between you and the stations.  Many times, on
   >a long meteor burn, I have heard as many as 4 or 5 different
   >stations being reflected one after the other, and *sometimes*, more
   >than one will be head at exactly the same time.  You can tell this
   >because of the fact that the stations are NOT  *exactly* on their
   >assigned frequency, sometimes deviating as much as 2 KHz ...
   >usually 1 KHz or less, but you will hear the difference in the beat
   >notes. Anyway, all you will need is a simple dipole antenna cut
   >reasonably close to the frequency of the video carrier for the
   >channel you wish to monitor ... you will enjoy what you hear, and
   >you'll know *immediately* if enhanced conditions are present as
   >soon as you walk into the shack! 73,     Ron    W0PN/3      FM19jf

   >Hello all,
   >Does somebody know if the upcoming Leonid shower can be detected by
   >radio? In other words, does the entry of meteorites into the earth's
   >atmosphere produce detectable signals? If so, which frequency
   >spectrum has to be monitored?
   >BTW I'm not referring to meteor-scatter. I'm wondering if an
   >entering meteor itself produces a signal.
   >Thanks for your reply!
   >Best regards,
   >Frits Westra -- fwestra@hetnet.nl
   >Netherlands
   >Net-Tamer V 1.11.2 - Registered
   >---
   >Submissions radio-astronomy@qth.net


Best regards,
Frits Westra -- fwestra@hetnet.nl
Netherlands

Net-Tamer V 1.11.2 - Registered


---
Submissions radio-astronomy@qth.net





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