Re: [DX] [FM-jupinaa] Satelliittikusoilu?

[ilkka suni <is.sit@xxxxxxxxxx>]

At 09:07 16.2.2014, you wrote:
> Satelliitit taitavat olla
> normaalisti niin pienikokoisia, että niistä ei saa
> suoraa heijastusta.


JUUANTEEKSI, TUOSSA muistin vajavaisesti. Mahdollisen oikaisun varalta
lainaan kirjoituksensa tähän.
 
I apologize for this, but as I gather this posting is allowed to quote.
The following is by Mr Jean-L. Rault::



Hi all

Please be assured that the reception of ground VHF transmissions
reflected by space stations is possible with amateur means.

More than 12 years ago, I tried with Philippe F6ETI to use the MIR
russian space station as a VHF space reflector.
And it worked :o)

Please look at

http://ph-martin.pagesperso-orange.fr/f6eti/mir/index.htm for some
details (sorry, it's in french).

Doing the same nowadays with FM broadcast transmitters should be an
affordable challenge.

On the negative side:
- FM broadcast uses more bandwidth than we used for our CW -telegraphy-
tests (thus decreasing the SNR  -signal to noise ratio-), 
- FM band is generally crowded by local, contiguous and loud transmitters
- FM band uses lower frequencies than the 144 MHz ham band (thus
decreasing the ERS -equivalent radar surface- of the space target)
- Commercial FM receivers seem to be often less sensitive than ham radio
receivers generally fitted with LNAs (low noise amplifiers)

On the positive one:
- ISS presents a much larger ERS (equivalent radar surface) than MIR
- FM broadcast transmitters are radiating a much much higher ERP
(equivalent radiated power)  than ham stations (Hundred of kW 
instead of tens)

IMHO, the key to success for FM space bodies radio reflections is to
precisely determine the time of occurence of such reflections. We -as
amateurs- have to use specular reflections.This specular reflections time
détermination depends mainly on the geometry (location of transmitters,
observation location and space reflector trajectory and
orientation).

Hope it helps :o)

Jean-Louis F6AGR
Former AMSAT-France president

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