[amsat-bb] Re: Redundant geostaionary birds?
rogerkola at aol.com
Sun Jan 28 17:32:33 PST 2007
"I don't know of any GEO sats that have uplinks within amateur bands.
The ones I know about all seem to be either CO-band or Ku-band, and
have uplinks in the 5.9 GHz (C-band) or 14 GHz (Ku-band) ranges."
This could be a "commercial" venture where AMSAT "buys" uplink frequencies,
licenses and "resells" access to it's members. It might set a precedent that
we are willing to "pay" for RF use however...
----- Original Message -----
From: "Bruce Bostwick" <lihan161051 at sbcglobal.net>
To: <amsat-bb at amsat.org>
Sent: Sunday, January 28, 2007 5:26 PM
Subject: [amsat-bb] Re: Redundant geostaionary birds?
> I don't know of any GEO sats that have uplinks within amateur bands.
> The ones I know about all seem to be either C-band or Ku-band, and
> have uplinks in the 5.9 GHz (C-band) or 14 GHz (Ku-band) ranges.
> While it's quite possible that the sats are accessible from anywhere
> on earth that's in their footprint, you'd need an appropriate license
> to transmit on the correct uplink frequencies to get into the
> transponders .. at least legally ..
> GEO sats are also moved to a junk orbit when they run out of
> stationkeeping propellant, so they're no longer geostationary and
> drift quite a bit from day to day. You wouldn't need much steering
> on a dish to track one, and wouldn't need more than one axis as far
> as I know, but you would definitely need to maintain good keps on the
> bird to be able to keep it in the middle of your main lobe. And you
> would need at least 50-100 watts of uplink to get a usable downlink
> signal (as i recall, a full-bandwidth analog TV signal took about 600
> watts to get to GE-2 last time I watched an uplink in progress, I
> know some folks who can tell you far more than I could about this..)
> and you'd need a feed that could completely reject the uplink to keep
> from desensing your downlink receiver. (You definitely want to do it
> full duplex!)
> Could be entertaining, if the legalities could be worked out, but I
> don't know if any of the dead sats can be accessed using ham freqs,
> or what the consequences would be of a ham downlink coming down on
> commercial frequencies. (Bear in mind that if the sat is too close
> to the location of an *active* sat, and transmitting, its downlink
> might interfere with the downlink of the one it's passing behind, or
> you might get into the uplink of the active bird, or both. Could be
> a real mess.) In short, probably impractical for North America and
> Europe/Africa. More remote parts of the world could have some fun
> with this though ..
> (Lots of additional useful info available at http://www.lyngsat.com/)
> On Jan 28, 2007, at 10:54 AM, Andythomas wrote:
> > Then I fell to wondering:
> > whether we in the amateur satellite service could not use both the
> > up and
> > down links on these redundant geostationary birds?
> > I don't know the exaxct frequencies but there may be one out there
> > that has
> > frequencies we share (or at least the uplink). After all we have
> > years of
> > experience of chasing staellites which are not exactly where they
> > should be
> > in the sky and so the "wandering geostationary" satellite shouldn't
> > be a
> > worry.
> > I think each transponder channel is 27 MHz wide??
> "No, I'm disagreeing with you. That doesn't mean I'm not listening to
> you or understanding what you're saying. I'm doing all three at the
> same time." -- Toby Ziegler
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
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