Interference with satellite signals

I’m hoping there are factual answers to this, but of course, the appropriate mods should relocate this if it makes sense to do so.

I’ve had satellite radio in my two vehicles for a number of years. There is an intersection (a Single Point Urban Interchange, to be specific) near my house that I cross over almost daily. Regardless of which car I’m in at the time, if I’m listening to satellite radio, the signal will cut out at some point while I’m crossing the intersection. Or, if I’m stopped at the light at the intersection, the signal will remain out during my entire time at the light. The same thing used to occur at a specific four-way signal in Van Nuys when I still lived in LA.

I don’t have any issues with radio, cell or bluetooth signals at the current or the prior intersection. Other than traffic signals and the associated cameras/sensors, there isn’t anything obvious overhead at either location.

So, what types of equipment and/or materials are capable of interfering with a satellite signal? I’m aware that storms can cause problems with my satellite at home, but the problem I describe here happens 100% of the time at these specific locations, regardless of weather.

I have no idea of what’s causing it, but I experience the same sort of issue with the satellite radio in my car. I’ve discovered a few spots where I pretty consistently lose the signal for at least a few seconds, until I drive out of the area. One spot is just to the east of O’Hare, so I wonder if that one is related to equipment or signals from the airport. The other is just south of downtown Milwaukee, on I-94, and there’s nothing that’s obviously “there” to cause it.

I believe satellite radio satellites are in geostationary orbits over the equator, so the signal path (in the northern hemisphere) would be coming from the south, not so much “overhead”. Depending on your latitude, the angle can be fairly low. Low enough to be blocked by large buildings of a row of trees.

SiriusXM apparently has satellites from both of its legacy companies, Sirius and XM. According to the link below, the two sets of satellites use different positioning in their orbits. The XM satellites, and the later Sirius satellites, are in geostationary orbits, but the original three Sirius satellites are in “analemma” orbits, appearing to move north and south over the Western Hemisphere in a “figure eight” pattern, with two of the three being (relatively) overhead in North America at any given time.

My non-scientific guess is that this isn’t the issue. I spent a great deal of time driving in downtown LA (around and in-between very tall buildings), and never had any interference issues unless I was inside a concrete parking garage. So I’m thinking this is more than just a line-of-sight problem.

One of the things that you may not realize about satellite radio is that, in major cities, they get around the problem of line-of-sight signal blockage (due to tall buildings and bridges) with “terrestrial repeaters” – essentially, traditional radio broadcast signals. Your radio uses the satellite and terrestrial signals to pull together the audio stream. As long as your radio can pick up at least one of the two sorts of signals, you can still get the broadcast stream.

Here in Chicago, I can go into a parking garage, or even drive underground (like on Lower Wacker Drive), and still get a Sirius signal, thanks to the terrestrial boosters. But, if I go into a parking ramp out in the suburbs (far enough away from downtown that I’m out of range of the booster signal), I’ll lose my Sirius signal almost immediately.

Some device that transmits on a frequency close to what the satellite radio uses might do this. It’s probably of low power, meaning you have to be close to it to notice the problem.

It could be multipath error. Some signal reflects off a surface a distance away and arrives at the reciever a little after the signal direct from the source. The reciever can’t tell that it’s getting two signals, it just looks like one jumble. It cuts the audio until it can decode the signal again.

I get the same problem on my drive home every day. One otherwise un-notable intersection in a development is a dead zone for SiriusXM. Nowhere else on my drive, just there.