Basic technical question

[Dawgsfan]

Apologies for this very basic question. When driving and listening to SiriusXM, is the antenna on the exterior of my car pulling in a signal from a single satellite, or does the antenna pull from different satellites as I travel? Trying to understand why my SiriusXM reception is perfect while in motion, while my home DirecTV dish wouldn’t be able to maintain a signal if it were in motion.

Thanks!

 

[NYDutch]

Apologies for this very basic question. When driving and listening to SiriusXM, is the antenna on the exterior of my car pulling in a signal from a single satellite, or does the antenna pull from different satellites as I travel? Trying to understand why my SiriusXM reception is perfect while in motion, while my home DirecTV dish wouldn’t be able to maintain a signal if it were in motion.

Thanks!

There are in motion satellite TV dishes, but there are significant differences in the dish/LNB requirements for satellite radio and satellite TV reception because of the differences in the transmitter strengths used and the bandwidth required for each service. Bottom line, satellite radio needs much less for an antenna than satellite TV.

 

[arlo]

If I'm not mistaken. SXM is rebroadcast to satellite tv as a part of the subscription add on.
Your satellite system is receiving a signal in the 12-ish GHz frequency range. It needs a dish antenna to focus and amplify the weak signal.
SiriusXM satellite actual is kind of like your GPS receiver. The received radio frequencies are much lower in frequency and can travel farther and don't have to be focused in a tight beam.

Straight from the horses mouth:

Sirius satellites broadcast within the S-band frequencies from 2.3200 to 2.3325 GHz, while XM radio uses adjacent frequencies 2.3325–2.3450 GHz.

If satellite TV in the 12 GHz range were able to be received w/o a dish and high gain amplifier on the ground, you would probably feel like an egg in a microwave oven.

 

[Bobby]

If I'm not mistaken. SXM is rebroadcast to satellite tv as a part of the subscription add on.
Your satellite system is receiving a signal in the 12-ish GHz frequency range. It needs a dish antenna to focus and amplify the weak signal.
SiriusXM satellite actual is kind of like your GPS receiver. The received radio frequencies are much lower in frequency and can travel farther and don't have to be focused in a tight beam.

Straight from the horses mouth:

Sirius satellites broadcast within the S-band frequencies from 2.3200 to 2.3325 GHz, while XM radio uses adjacent frequencies 2.3325–2.3450 GHz.

If satellite TV in the 12 GHz range were able to be received w/o a dish and high gain amplifier on the ground, you would probably feel like an egg in a microwave oven.

Um, he's not talking about XM over Dish. He was specific about the radio in his car.

 

[arlo]

Um, he's not talking about XM over Dish. He was specific about the radio in his car.

"while my home DirecTV dish wouldn’t be able to maintain a signal if it were in motion."

 

[Bobby]

"while my home DirecTV dish wouldn’t be able to maintain a signal if it were in motion."

Gotcha!

 

[Jimbo]

So, does anyone know the answer to his original question ?

When driving and listening to SiriusXM, is the antenna on the exterior of my car pulling in a signal from a single satellite, or does the antenna pull from different satellites as I travel?

 

[arlo]

Does this help? I would say wherever the signal is strongest.
If you really want to get technical:

SiriusXM Satellite Radio (info for techies)

Oh. And this too:

SiriusXM – Satellites and Repeaters | SiriusBuzz

As most investors and consumers are aware, SiriusXM delivers content to consumers via satellite. What many are likely unaware of is the fact that the satellite signal is supplemented by a repeater network. The repeater network allows you to receive your signal in areas where the satellite signal...

siriusbuzz.com

SiriusXM Radio uses two satellites appropriately named “Rhythm” and Blues” placed in parallel geostationary orbit, one at 85 Degrees West longitude and the other at 115 Degrees West longitude.

 

[Dawgsfan]

This is awesome! Thanks.

 

[cpalmer2k]

They can pick up and use the signal from any of the satellites capable of feeding the type of radio in your car. At home I have an older commercial XM receiver that actually has three XM tuners and audio outputs on it. I have one of the Terk amplified antennas and I specifically aimed it between two satellites to try to avoid weather outages from clouds as much as possible.

Keep in mind there are radios that can only receive the Sirius satellites, those that can only receive XM satellites and I believe there are some that can receive and use signals from either one. The older original Sirius satellites moved in an odd figure 8 orbit pattern, while the XM and the newer SiriusXM satellites (that can serve a Sirius radio, an XM Radio, or the newer radios) are geostationary (meaning you always point to the same spot in the sky to pick up the signal). I remember back in the day I had a home Sirius radio because they had the NFL package at the time and depending on how cloudy it was I lost reception indoors even with one of those Terk panel antennas because of the movement. The XM based tuners and the newer ones are a lot more stable and forgiving when it comes to weather.

 

[cpalmer2k]

Here is more info from Wikipedia:

Sirius satellites broadcast within the S-band frequencies from 2.3200 to 2.3325 GHz, while XM radio uses adjacent frequencies 2.3325–2.3450 GHz.[121][122]

Functional satellites[edit]​

• Sirius FM-5 (Radiosat 5) - Launch occurred on 30 June 2009.
• Sirius FM-6 (Radiosat 6, COSPAR 2013-058A) - Launch occurred on 25 October 2013.[123]
• XM-3 (Rhythm, COSPAR 2005-008A) - Launch occurred on 28 February 2005.[124]
• XM-4 (Blues, COSPAR 2006-049A) - Launch occurred on 30 October 2006.[124]
• XM-5 (COSPAR 2010-053A) - Launch occurred on 14 October 2010.[125]
• SXM-8 - Launch occurred on 6 June 2021, by a SpaceX Falcon 9 launch vehicle.[114]

Defunct satellites[edit]​

• Sirius FM-1 (Radiosat 1) - Launch occurred on 30 June 2000.
• Sirius FM-2 (Radiosat 2) - Launch occurred on 5 September 2000.
• Sirius FM-3 (Radiosat 3) - Launch occurred on 30 November 2000.
• Sirius FM-4 (Radiosat 4) - Ground spare, was not launched into orbit. In October 2012, it was donated for display to the National Air and Space Museum's Steven F. Udvar-Hazy Center.[126]
• XM-1 (Roll, COSPAR 2001-018A) - Launch occurred on 8 May 2001. Retired in 2016 (graveyard orbit).[127]
• XM-2 (Rock, COSPAR 2001-012A) - Launch occurred on 18 March 2001. FCC license expired in 2014.[127]
• SXM-7 - Launch occurred on 13 December 2020[128] by a SpaceX Falcon 9 launch vehicle, and was intended to replace satellite XM-3.[129] On 27 January 2021, Sirius XM announced that the satellite suffered failures during in-orbit testing, but did not provide detail on the nature of those failures.[130]

 

[kshaw]

I have one of the SXM boom boxes that works with an Onyx Plus or Tour 360L. As I recall, the documentation said that it picks up signals from both satellites and terrestrial stations. I have no idea if automobile systems have the same setup. It used the same antenna as the home SXM systems and the automobile antenna would not work with that radio.

 

[TheKrell]

I have no idea if automobile systems have the same setup.

I am pretty sure they do, but I have no way of verifying that.

 

[Don in CT]

How do the ground repeaters sync up with the satellites.

 

[TheKrell]

How do the ground repeaters sync up with the satellites.

There is considerable skew between these sources and it is my understanding that the receiver caches a second or two to allow it to switch tuners seamlessly for best reception. I don't know that for sure either.

 

[tobsandmags]

I’ve been wondering what happened to the repeaters. I recall something about getting rid of them or drastically reducing them. Is there a recent map showing them. The only I could find is quite old.


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