Satellite Radio and the Sunroof

[Nashional]

I've had some pretty bad reception with XM and have been blaming it on the summer/full trees along the highway in many areas where I travel.

A few days ago, I installed a new XM system in my wife's car. When she came home I asked here if it dropped out in the same places. She said she didn't have any drop-outs at all.

Well, by accident today, I figured out the issue with my Camaro and it is 100% reproducible. If the sunroof is open (at all), XM starts dropping really bad, especially heading north with tall trees along the sides of the road. If the sunroof is completely closed, I have no drop-outs at all.

Anyone else?

[Burlap]

Sounds like a loose wire/short. Bring it in.

[BlueMarlin]

Just curious, how do you fit in the car with the sunroof? I'm close to 6'6'' and with no sunroof I barely just fit.

[OUR72GTO]

We noticed more XM dropping while north of TALL trees with the roof open.

[ssdavidw]

When the sunroof is open, doesn't the glass slide over the antenna? It shouldn't totally wipe out your XM reception but it sure won't help it either.

[badkarma]

i've also noticed that the BA system has more dropouts than my Kenwood in my GTO.

I think it may have something to do with the buffering of data. The BA seems to have a smaller buffer. I do not have a sunroof.

For those who don't know what buffering is, the unit is storing music data in memory before it plays it. You can tell if your unit is buffering if you sit under an overpass or other obstruction and the music keeps playing for a bit and then cuts out until you clear the obstruction. The BA system cuts out much sooner than my Kenwood. (same overpass I go under everyday)

It should also be noted that XM has several ground repeaters in certain areas that keep the signal going even in these situations.

Also, this is going to sound funny but at least with conventional antennae some of the signal actually comes from the signal bouncing off a surface such as the car's body and to the antenna. Maybe that is happening with the sunroof being angled differently when open.....or if is a type of glass that actually blocks energy, it could be doing that too.

[Nashional]

I can sit in my garage with the garage door open and listen to XM. (The opening is to the east.)

If I open the sunroof, even partially, I get no reception at all.

Where exactly is the antenna? Is it not in the black plastic above the rear window on the root? If it's in there, then the sunroof never comes close to covering it.

BlueMarlin, I"m 5'10" and I fit with no issues in the front.

[Rogue Leader]

I definitely notice worse reception with the sunroof open, but its not completely horrible. It also depends on the time of day due to the angle of the sun. my original Sirius player from 5 years ago was notorious for this however they made it better over time. That said the car hardly buffers anything, even the cheap aftermarket players buffer better than this. I hope someone comes up with an upgraded XM module for this car (doubtful) because the sound quality is pretty poor (makes my speakers rattle), and reception can be spotty. Maybe if there were more ground repeaters, I guess Sirius just had a better signal, I had my Sirius antenna mounted INSIDE the rear bumper of my vette and it got better reception than this and the sound quality was better through the FM tuner!

[Nashional]

Here's a video of the XM cutting out issue.

While driving in a northerly direction and the sunroof is open, XM keeps cutting out. This video covers 1 mile of road. I count at least 8 times the signal drops out completely.

Driving south or with the sunroof closed, there are zero drop-outs.

Sorry for the classical music, but YT kept ripping out the audio when I tried pop music.

[levi1922]

Originally Posted by badkarma

i've also noticed that the BA system has more dropouts than my Kenwood in my GTO.

I think it may have something to do with the buffering of data. The BA seems to have a smaller buffer. I do not have a sunroof.

For those who don't know what buffering is, the unit is storing music data in memory before it plays it. You can tell if your unit is buffering if you sit under an overpass or other obstruction and the music keeps playing for a bit and then cuts out until you clear the obstruction. The BA system cuts out much sooner than my Kenwood. (same overpass I go under everyday)

It should also be noted that XM has several ground repeaters in certain areas that keep the signal going even in these situations.

Also, this is going to sound funny but at least with conventional antennae some of the signal actually comes from the signal bouncing off a surface such as the car's body and to the antenna. Maybe that is happening with the sunroof being angled differently when open.....or if is a type of glass that actually blocks energy, it could be doing that too.

my after market receiver has way more buffer than any factory system i have been in. its usually about 6-8 seconds. it only cuts out if im stationary under the overpass or gas station

Originally Posted by OUR72GTO

We noticed more XM dropping while north of TALL trees with the roof open.

yeahh, the satellites are above the equator, so the trees are between you and the satellites, its very annoying.

[BackinBlack]

XM101:

XM is a geostationary based satellite broadcast. This means that the satellites are always in the same position in the sky relative to the earth. If you look on a map of the US, their two satellites are located at 85 degrees West Longitude and 115 degrees West Longitude. XM's "Rock" and "Roll" orbit at these positions, with "Rock" over the East Coast and "Roll" over the West Coast.

No matter where you are in the US, your reception is dependant on a straight line of sight to these two points in the sky. There is also a terrestrial repeater network, but these are strategically located in urban areas where XM knew tall buildings and certain geography would interfere with their satellite signals on passive mobile receivers. You may or may not be near a terrestrial repeater...it depends where you live/drive.

When you open your sunroof, or enter your garage, or drive under a canopy of trees, you will interrupt that LOS as badkarma described.

GM knows about the sliding sunroof issue as it happened on others cars going back to 2005 or 2006 (I can't remember exactly when). A new dual-tuner diversity system was designed and implemented on vette convertibles and some of the cars that had the sliding sunroof where that sunroof would always obscure the antennae. But this is a more expensive system and definately was not included with the new Camaro.

If this reception drop is 100% repeatable in the same place and under the same conditions then don't bother looking for failure modes in wiring or anything because it is simple geometry and the dealer won't be able to fix it.

[Nashional]

I've been an XM subscriber since October 2001 (one of the first 250,000 subscribers). I'm aware of how they work (I'm also an IT Professional and a gadget geek).

I also have a $6,000 truck and a $50 XM radio. No dropouts. My wife's Camary has no dropouts.

Regardless of the cause of the issue, there is no way this should be happening on a $40K+ vehivle.

It is not acceptable that in the years of design/pre-production of this car, no one thought of this as an issue? Everyone should expect better than this of GM. I do.

[FI4T0MCAT]

You know mine does that same crap, and its with the sunroof closed. I have yet to open my sunroof, but i stopped listening to xm because it kept cutting out.

[Cheshirelaugh]

I've got a sunroof too... I like XM OK but the cut-outs just aren't worth the money.
C&C Package + 160 gig iPod FTW!