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

Hi Andy,

I have often wondered the same, whether amateurs could use out-of-service geostationary birds, but the reality is:

1) Most end-of-life geo-stat birds should get moved into a "disposal orbit" well above 22,240 miles. The geo-stat parking spots are precious and must be reused.

2) If for some reason a bird could not get into parking orbit, its probably dead (e.g. no power, comms, etc). Drifting will begin, and the spacecraft will probably move into a geo-sync orbit (figure eight around its initial geo-stat orbit) and slowly toward the equilibrium points. For this reason every effort is made to move the spacecraft into the super-sync disposal orbit.

3) Most of the uplink freq's are in the 5.9 GHz range (out of our allocation) and downlink in the 3.7 GHz range, again, (out of our allocation).

There was a plan for a C-band to C-band transponder on Eagle, but that has been dropped.

I heard that several years ago there was talk of putting an amateur transponder onboard a commercial geo-sync bird. But I suspect economics and the fact that all extra mass is reserved for stationkeeping fuel. Plus power is always critical, and over time, the solar panels generate less. Anyone know more about this?

73,

Dave NøTGD

On 1/28/07, Andythomas [email protected] wrote:

Hi gang,

I was reading an ESA press release about satellite radio experiments and didn't realise its emphasis on re-using redundant broadcast tv satellites until I read the bbc version of the story at:

http://news.bbc.co.uk/1/hi/technology/6301359.stm

which explains that when the broadcast geostationary saetllites lose fuel for position control the tv guys lose interest in them, even though the transponders work fine.

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??

I remember vaguely that there was a "pipe" on one of the birds from the UK to the USA which was used in amateur service about 15 years ago now (but I don' t remember very much else).

If we could take over one channel on the transponder then immediately we would start looking at uplink equations, multiplex etc. and what about a mobile aprs service?!

90% of the world will tell you why it can't be done. Who can show how it can be done?

73 de andy G0SFJ

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