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Re: (meteorobs) Radio Meteors (long)
Conrad asked:
> Thanks for the explanation, but I wanted to know if you could
>use the same
>concept to pick up pulsar or quasar signal's.
No: the concept involved is a very different one. Detecting meteors uses
a "radar" like technique; that is, using man-made radio transmissions to
"illuminate" the meteor zone in the upper atmosphere, and then listening
for radio returns, or echoes. By contrast, pulsars and the like are
distant, very weak, discrete radio sources on their own, but require a much
more sensitive and specialized set of equipment for detection than what I
have described. A good source for information on amateur equipment and
techniques in this area is the Society of Amateur Radio Astronomers (SARA).
>Also, what would you hear when your listening for meteor echoes.
In forward-scatter, the meteor trail will create a very sudden, but rather
briefpropagation path between the distant transmitter and yourself. In the
method I described, you should normally hear only background hiss or static
when no events are present. When a meteor event occurs, you will hear a
brief "burst" of whatever it is the distant tramsmitter is broadcasting
(voice, music, etc.) These bursts can last from less than a second up to a
few minutes, and will often sound distorted or garbled. The shorter events
should always be more numerous with the very long events quite rare.
WARNING: distinguishing true meteor events can often be very problematic
using this monitoring method. This point cannot be stressed enough.
Several other forms of radio wave propagation can also cause events,
including tropospheric scatter, Sporadic E, D-layer scatter, temperature
inversion ducting, and aircraft reflections. Shorter range sysstems are
especially prone to reflections from aircraft.
I personally much prefer a system which utilizes a BFO equiped receiver to
monitor echoes of the carrier wave signal itself, rather than the
modulation. Audibly, the meteor echoes are usually very distinct compared
to other propagation modes, and much more information can be gleaned from
them. There are also several tests which can be applied to verify that
true meteor signals are being received.
>....how do you analyze and collect
>the data?
>
Many amateurs simply enjoy listening themselves and logging their data on
paper. Strip chart recorders and taping techniques have also been commonly
used. There are now several amateur developed personal computer based
systems which automatically collect meteor event data; ranging from counts,
to to specific parameters, to recording full event signatures. It all
depends upon what the amateur or their organization wishes to do with the
data.
Analysis techniques cover a broad range of methods. Meteor count data is
frequently used in statistical studies of sporadic and shower flux
behavior. Other collected parameters open the door to several additional
areas, such as physical properties of the meteor trail, and
characteristics of the meteoroid which produced it, including velocity and
orbital information. There is much more to it than I have room to outline
here.
I have tried to be rather concise with these answers, so if you have
further questions which may not be interest to the entire list, feel free
to contact me via private e-mail.
Take care,
Jim
James Richardson
Graceville, Florida
richardson@digitalexp.com
Operations Manager / Radiometeor Project Coordinator
American Meteor Society (AMS)
http://www.serve.com/meteors/
References: