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Re: lower frequency downlinks



Remember that these were all LEOs, where you can tolerate a smaller (in
terms of wavelengths) lower efficiency antenna. I beleive that all of these
launches were either free or heavily subsidized so space was less of a
problem. A HEO magnifies the problem as you need gain to overcome the
additional path loss.

73,

John
KD6OZH

----- Original Message -----
From: "Al copland" <allan_gm1sxx@hotmail.com>
To: <amsat-bb@amsat.org>
Sent: Tuesday, January 31, 2006 19:51 UTC
Subject: Re: [amsat-bb] lower frequency downlinks


> Re the difficulty of accomodating antennae for lower frequency downlinks,
I
> believe it is a problem thats already been addressed quite successfully on
> small space-craft in the past.
>
> To the best of my knowledge (1), Oscars 5,6,7,9(AKA Uosat1) plus the
Russian
> RS series of birds carried antennae for the 10M band. On the Oscars,
> carpenter's tape antennae seems to have been the norm.
>
> Since there is not a great deal of data on the very popular but sadly
> defunct Russian RS birds, one has to suppose that they also used some sort
> of workable 10M antenna that fitted into a small space on the launcher.
> Although in some cases (I have no easy way to check this) such antennae
may
> have been compromised designs, the performance was generally pretty good
> with the RS birds in particular.
>
> Obviously a bird would have to have a low spin rate and not be tumbling
when
> such antennae are deployed, but deployable HF antennas are a proven
> technology, and not only on AMSATsatellites.
>
> 73 Al.
> GM1SXX
> (1) Information source.. The Satellite Experimenter's Handbook .
> ----
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