Sirius Satellite-vs-Amatuer Radio Satellite

[spdfile1]

This may be a stupid question and I may already know the answer, but I want to get a definitive answer. My answer is triangulation. Here is the question: My Sirius Satellite radio in the car gets it's signal via a satellite, and it almost never goes out of range!!!! How come the Amsat Oscar satellite's and similiar satellite's only have a few minute window of being in range before they go back out again?!?!?!

 

[W2NJS]

The Sirius and similar communications satellites are in stationary orbits about 22,000 miles up. The amateur satellites, as well as many "spy" satellites, orbit much lower and travel around the earth in continuous orbits. If you were able to see a Sirius satellite you would see it at the same place overhead all the time. The orbiting satellites would fly over your position every so often then disappear until they reappeared over the horizon after another orbit.

 

[tuffaznalz]

geosynchronous (geostationary) orbit -vs- geocentric orbit

 

[spdfile1]

Ok that makes sense. So then I guess why couldn't the AMSAT OSCAR satellite's be stationary as well so they are always in range? I'm guessing maybe it is to expensive?!?!?!?

 

[kayn1n32008]

Ok that makes sense. So then I guess why couldn't the AMSAT OSCAR satellite's be stationary as well so they are always in range? I'm guessing maybe it is to expensive?!?!?!?

Well not sure if it would cost more, but if the oscar satellite was in a geostationary orbit then it would only see the same patch of earth all the time and would not be usable to hams outside of its foot-print.

 

[spdfile1]

Well not sure if it would cost more, but if the oscar satellite was in a geostationary orbit then it would only see the same patch of earth all the time and would not be usable to hams outside of its foot-print.

Ok gotcha. Wouldn't be very fair if the same people got exclusive rights to it. Thanks for answering. Much more clearer now

 

[JPSan]

Here is some info, courtesy of wikipedia....A geostationary orbit is expensive and slots are limited and expensive in themselves. AMSAT, the amateur radio satellite corp, has the Phase 4 sat in design, but nothing firm for launch. Just FYI. Hope it gives you some better understanding..


Geostationary orbit - Wikipedia, the free encyclopedia

Geosynchronous satellite - Wikipedia, the free encyclopedia

List of satellites in geosynchronous orbit - Wikipedia, the free encyclopedia

AMSAT - Wikipedia, the free encyclopedia

 

[spdfile1]

Here is some info, courtesy of wikipedia....A geostationary orbit is expensive and slots are limited and expensive in themselves. AMSAT, the amateur radio satellite corp, has the Phase 4 sat in design, but nothing firm for launch. Just FYI. Hope it gives you some better understanding..


Geostationary orbit - Wikipedia, the free encyclopedia

Geosynchronous satellite - Wikipedia, the free encyclopedia

List of satellites in geosynchronous orbit - Wikipedia, the free encyclopedia

AMSAT - Wikipedia, the free encyclopedia

JPSan,

Thanks for the links. I am on wikipedia all the time. I will check them out!!!!

 

[mancow]

Actually Sirius uses a series of three satellies but they are in a strange orbit and are not geostationary.

Highly elliptical orbit - Wikipedia, the free encyclopedia

 

[CalebATC]

I knew about this, but never did know the names beside LEO..... thanks for asking this.

So, I have always wondered this- how do they put them in orbit? Seems like some of the military sats are always in the same locations, orbiting from left to right, or up and down, where the ISS is all over the place, is it the way/time/place they are put in orbit, or are all the sats at a very big change in altitude?

 

[mike_gain]

I remember reading in HAM magazines back in the 80's about V/Uhf repeater satellites that were "Comming Soon". You would be able to use 3-5 watt ht's and have a blast. I guess Motorola and the cell phone industry got to congress/fcc first. Or maybe just lobbyed better.

 

[prcguy]

There may not be any cost involved parking an amateur satellite in geosynchronous orbit because there is no competing business or frequencies involved. You can have many satellites parked in the same slot operating at different frequencies.

However, provisions for on-board fuel and crews to track and maintain station keeping would be very expensive.
prcguy

Here is some info, courtesy of wikipedia....A geostationary orbit is expensive and slots are limited and expensive in themselves. AMSAT, the amateur radio satellite corp, has the Phase 4 sat in design, but nothing firm for launch. Just FYI. Hope it gives you some better understanding..


Geostationary orbit - Wikipedia, the free encyclopedia

Geosynchronous satellite - Wikipedia, the free encyclopedia

List of satellites in geosynchronous orbit - Wikipedia, the free encyclopedia

AMSAT - Wikipedia, the free encyclopedia

 

[mancow]

They launch them atop of commercially owned rockets. Some military sats have gone up on shuttles.

The geostationary ones are always at the same spot in the sky because they match the speed of the earth's rotation. The rest are in various heights and orbits.

I knew about this, but never did know the names beside LEO..... thanks for asking this.

So, I have always wondered this- how do they put them in orbit? Seems like some of the military sats are always in the same locations, orbiting from left to right, or up and down, where the ISS is all over the place, is it the way/time/place they are put in orbit, or are all the sats at a very big change in altitude?

 

[Thunderknight]

I also believe it has to do with transmit power. To uplink (earth to satellite) to a geostationary satellite requires more transmitter power than a low earth orbiting satellite (LEO). I.e. I'm not sure you could use an HT to talk to a geostationary satellite like you can with LEO satellites. I think the Iridium and Globalstar satellite phone constellations are LEOs (or MEOs) for the same reason.

(To mike_gain: You can use HTs to talk to some ham satellites).

 

[prcguy]

If there were VHF/UHF geostationary amateur satellites they should work fine with a 5w handheld and a modest Yagi with less than 10dB gain. The current geostationary UHF military satellites were intended to be used with a 15w radio and about 6dBic antenna gain. Now there are 5w handhelds being used on these satellites with ok results.
prcguy

I also believe it has to do with transmit power. To uplink (earth to satellite) to a geostationary satellite requires more transmitter power than a low earth orbiting satellite (LEO). I.e. I'm not sure you could use an HT to talk to a geostationary satellite like you can with LEO satellites. I think the Iridium and Globalstar satellite phone constellations are LEOs (or MEOs) for the same reason.

(To mike_gain: You can use HTs to talk to some ham satellites).