What's the power level of these satellites?

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glen4cindy

glen4cindy

SatelliteGuys Pro
Original poster
Sep 14, 2004
641
38
St. Louis MO, area
Dish and Direct work with 18" to 24" or there-abouts, and our FTA dishes start out at 30" and go up from there.

I see that the Siruis/XM antennas are only like 2 inch squares or there-abouts.

This leads me to wonder just how powerful are these Sirius/XM satellites? Are they Geo-stationary like the TV communications satellites?

Hope all these have not been answered already. I have not been able to find them if they have.

Thanks.
 
I don't know about the power level, but I think I can answer the other part of your question.

XM has two satelittes in geo-stationary orbit, I think at 85W and 115W (I could be wrong). They do have spares, but I think only those two transmit currently. So if you have XM antenna, once you position it and get a signal (theoretically) you won't have to adjust it. This is for non-vehicular radios of course.

Sirius, has 3 satelittes in a "Figure-8" type orbit (I think it might be geo-synchronous) and at least two of them spend most of their time circling above N. America. There was a web site with an animation of how their orbits worked, but I can't remember where i saw it. So if you have a Sirius antenna, you might need to move it around during the day if you lose your signal, since the satelittes aren't in a "fixed" position.

Also, I know XM tells you to point your antenna south if possible, while Sirius says North (for most of the country) because the satellites spend most of the time slightly north of the center of the country.

I hope this poorly-written explanation helps, and please, somebody correct me if i gave any wrong info! I am very interested in how satellite broadcast technology works and I try to learn as much as possible. :)
 
Satellite radio requires less bandwidth to receive audio than satellite tv therefore it does not need as much of a signal to still receive good service. The more bandwidth needed the more signal / power is required.
 
I was not so much looking for position information as I was transmit power.

My current vehicle has XM built-in, but, my last vehicle, I had a unit installed and it had a very small square antenna not much bigger than a postage stamp. I just stuck it on top of my vehicle.

The first place I put it rather surprised me that it even worked. The rear door had very large hinges and there was quite a bit of space between the door and the hinge. I had the antenna stuck behind the hinge! I still got very good signal levels. The only reason I moved it was because that location did not provide a very good way to get the wire into the interior of the vehicle.

I figure with such a small antenna, the transmit power must be quite high, so it makes me wonder how big the solar arrays must be on the satellites. I don't think the Sirius antennas are much bigger.

Even the built in antenna on my vehicle is not really that big. Less than 4 or 5 inches square.
 
The reason I rambled about the positioning, was you asked if they are geo-stationary. I found the link of the orbit path if anyone is interested.

SIRIUS-1 - Orbit Data

I've had some surprising signal strengths as well, such as when my truck is completely in the garage with the garage door closed, etc. I wonder if Denver has a terrestrial repeater that would account for that. I know the ground based repeaters help a lot in big cities. In Las Vegas, I was getting a constant signal in massive parking garages, in the long highway tunnel near the airport etc.
 
Also another thing comes in to play... the frequency of XM and Sirius is in the 2.0ghz range I believe.

The figure 8 of the Sirius satellite birds is sometimes a disadvantage but for the most part it works out better. They don't need as many repeaters since their look angle in the northern states is much better than XM's birds. I heard a few years ago Sirius had plans to launch a geostationary satellite too. Best of both worlds...the figure 8 and the geostationary. Not sure how they were going to handle the hand offs of the "A/B" satellite channels though.
 
Aurora said:
The reason I rambled about the positioning, was you asked if they are geo-stationary.
Click to expand...


Yes, I appreciated that too. I wasn't being critical, I appreciate the answer. I first thought they may not be geo-stationary because most receiver's antenna's are in near constant motion such as in a vehicle. The antenna for satellite TV in a moving vehicle is a little more complicated.

BTW, I love the link.

Thanks
 

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