[meteorite-list] OT - FW: meteor detection in AM SW band

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:36 2004
Message-ID: <20030826231044.99666.qmail_at_web80506.mail.yahoo.com>

----------------- Forward Message --------------------

Date: Mon, 25 Aug 2003 12:38:46 +0200
From: "ht s" <hts33_at_lycos.com>
Subject: Re: (meteorobs) meteor detection in AM SW
band

ASART(more info:www.asartonline.org or Meteor Related
Links at meteorobs.org) is also trying to use FM bands
but as we couldn't find a free band, still working
on...
Any help is really needed, especially from East...

H. Tugca SENER

ANKARA-TURKIYE

PS: There were really good seminars at 23.08.03.
Many thanks meteorobs, especially Marco Langbroek,
George Zay, Kim Y. and Peter Jenniskens...

- --------- Original Message ---------

DATE: Fri, 22 Aug 2003 16:47:16
From: "drobnock2" <drobnock_at_penn.com>
To: meteorobs_at_atmob.org
Cc:

>Hi:
>I remember seeing an article that discussed scatter
in the 10 and 11 meter band using AM modulation. If I
remember my propagation theory and it's relation to
radio astronomy, the 10 meter band is at the threshold
for radio astronomy.
>
>George John Drobnock
>
>--- In meteorobs_at_yahoogroups.com, Marcelo Kaczmarech
<meteoro_at_t...>
>wrote:
>> Please, somebody know some thing about forward
meteor scatter
>> detection using AM radio band or short wave band?
>> I hear about this in the Web but
>> I don't found more details.I have sucessfully
detected meteors in
>> VHF band, but the signals are weak and at low
hourly rate.
>> Thanks!
>>
>> Marcelo
>>

------------------------------

Date: Mon, 25 Aug 2003 14:07:48 +0200 (CEST)
From: Miguel Angel EA4EOZ <ea4eoz_at_ure.es>
Subject: Re: (meteorobs) meteor detection in AM SW
band

I made some experiments on 10m band using ham beacons,
like DL0IGI and DK0TEN, and the results were very
poor, mainly because the extremally low signals (FFT
soft a must). It's much better around 50 MHz with the
KW TV stations :-)

Greetings!

------------------------------

Date: Mon, 25 Aug 2003 14:01:09 -0000
From: "drobnock2" <drobnock_at_penn.com>
Subject: Re: (meteorobs) meteor detection in AM SW
band

Hi:
 See -- C. R. Kitchen, "Astrophysical Techniques,"
Adam Hilger, Ltd.,
1984 revised 1991.

Kitchen makes the statement that in radio astronomy -
scatter radio is within this astronomy - the sky is
transparent for electromagnetic radio between 10mm and
10 meters (microwave to 25 mHz). He further states
that electromagnetic radiation greater than 50 meters
(transmitted from earth) fails to penetrate the
atmosphere and is reflected back into the atmosphere.

The 10 and 11 meter bands are on the threshold of
frequencies to be reflected from an ionization trail.


It is a chalange to see how many stations can be
received.

George John Drobnock

------------------------------

Date: Mon, 25 Aug 2003 15:51:30 -0400 (EDT)
From: Michael Linnolt <mlinnolt_at_alum.mit.edu>
Subject: Re: (meteorobs) meteor detection in AM SW
band

These statements regarding the transparency of our
atmosphere to RF are a substantial oversimplification,
and hence not really accurate.
The transparency of our atmosphere (actually the
ionospheric layer) to vertically incident waves is
given by the parameter fc (critical frequency).
Frequencies above fc penetrate through to space, while

those below are reflected back to earth. fc varies
tremendously with time of day, geographical location,
season, 27-day and 11-year solar cycle. It can be as
high as 50-60Mhz (6 meters) during daytime 11-year
solar maximum, and as low as 1 Mhz (300 meters) during
night at solar minimum. In addition, the transparency
is a function of angle of incidence, which along with
fc, determines the MUF (maximum usable frequency) for
HF radio transmissions. MUF more closely tracks the
frequencies of interest for any meteor scatter work,
since it deals with propagation at the typical low
incidence angles for terrestrial signals. MUF varies
from a high of around 70Mhz to a low around 2-3Mhz.
 
 The science of ionospheric radio wave propagation is
complex, with sophisticated models and software
available to track these parameters and frequencies,
in near real time. Anyone interested in using these
range of frequencies for meteor scatter should be
aware of these issues, and not rely solely on
oversimplified and generalized statements as presented
here by CR Kitchen.
 
Mike Linnolt

------------------------------

Date: Mon, 25 Aug 2003 20:22:23 -0000
From: "drobnock2" <drobnock_at_penn.com>
Subject: Re: (meteorobs) meteor detection in AM SW
band

Hi:
You are correct about the complexity of
electromagnetic propagation, and there are may many
texts and papers written about the propagation of
radio signatures and computer programs to determine
MUF.

But I believe in the "keep it simple." If an
individual is interested in experimenting, start with
the simplist of tools and basic of readings.

Who was it that said.... "to enjoy meteors, all you
need are your eyes ?"

George John Drobnock

------------------------------

Date: Mon, 25 Aug 2003 17:22:50 -0400 (EDT)
From: Michael Linnolt <mlinnolt_at_alum.mit.edu>
Subject: Re: (meteorobs) meteor detection in AM SW
band

Yes, I think it is good to encourage experimentation
and recruit new radio observers. The purpose of my
message was just to alert new observers to the
potential for getting "bad data", if not fully aware
of other factors that affect reception of radio
signals.

Ionospheric propagation must always be monitored
(preferably by real-time MUF plots) while collecting
radio meteor data, especially the lower the frequency
employed. Even FM band (100Mhz) is subject to random
Es (sporadic E) and F layer propagation must be
considered around the 11-year sunspot maximum if using
frequencies around 50-60 Mhz. Tropospheric ducting is
another phenomena in this frequency range, which could
play a role, and is quite difficult to predict.

I suspect that the existing radio meteor database is
"polluted" to some degree by other propagation modes.
With Es being the major culprit.
Therefore, the radio meteor counts do represent some
degree of overestimation of meteor activity.

Mike Linnolt

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Received on Tue 26 Aug 2003 07:10:44 PM PDT