Then it's probably the receiver itself. If it's an older receiver, more than a year or two, then it's probably a case of it not being able to pull in the reduced bandwidth of about 35 stations that had their footprint reduced when Sirius and XM Merged their signals on the satellite. But some new radios have the problem, too. More of a Sirius radio than an XM radio problem, though. Remember back the last time they changed some of the channel lineup? That's when it happened. When you're in the middle of nowhere the signals are good enough, but when you get near large cities the plethora of radio signals crowds the radio spectrum and the weaker signals from those channels can't get through. It doesn't matter if your under and overpass (although you'll lose a signal for several seconds after passing under one) or not, the signal is degraded. Some cities have terrestrial towers that repeat the signal to make it stronger so that doesn't happen, but many do not.
There used to be more repeaters, but because of the agreement between the two satellite companies (now just the one) and terrestrial radio, the number of repeaters have been reduced. It used to be that all Satellite radios all had 10 second buffers when the service was first offered. Go under an overpass and the radio's buffer would already have the next XX seconds of programming and your radio kept playing without interruption. It's great except that meant the signal had to contain 10 seconds of programming at any given time but that was the only way to overcome blockages while driving where terrestrial repeaters were not present. Sirius and XM buffers are different, but similar in the way they work.
Each satellite puts out a direct feed and a delayed feed. Your receiver samples up to five feeds, a direct and a delayed feed from each of the two active satellites plus a terrestrial repeater and while each of the five signals are coming and going, fading in and out, derives an audio output from the five received signals that is close to 100% solid.
Over the years as the number of channels have proliferated but the bandwidth has remained constant, satellite radio has had to find more ways of cramming more channels into the signal. One way has been less bits per channel, but another way has been to reduce this buffer size. For most channels it's about a 2 second buffer now. So passing under an overpass for more than 2 seconds results in loss of signal momentarily, sometimes for 5 or 10 seconds until it reacquires the signal. This would also be true with moist tree leaves (really good blockers for S-Band) but not for rain which S-Band goes right through. The reason for the lower amount of buffer time is mostly to save bits when compressing since the current and delayed signals would be more similar.
One effect of the merger was that both Sirius and XM broadcasts had to add a large number of channels to each channel lineup and this means less bandwidth per channel, including the buffer size. So combine some wet leaves or an overpass with a reduced amount of buffer, along with an increase of local RF near big cities, and you will get more dropouts, generally.
In addition, the antennas have gotten smaller and smaller. This is done by using more and more power to the antenna to boost the signal. This is another situation where the lack of buffer combined with a greater chance of a signal drop-out due to the smaller antenna makes for more interrupted channels. A smaller antenna means more of a chance of programming loss.
It's like the remote control for my Fan-Tastic Fan Vent. When I'm in the boonies the remote works perfectly, but when I'm near a large city the remote is dead, often even if I hold the remote just a few inches away from the fan. The reason is the extraneous RF interference that's found in and around urban areas (more radio stations, police and emergency radios). I had to reprogram the remote control to use more power when communicating with the fan.
All that, plus fewer terrestrial repeaters, and there ya go.
With some Sirius and XM (and SiriusXM) radios, there is a firmware upgrade that solves the problem (most of those are factory installed radios, though). With others the only solution is to replace the receiver with a new one. Sometimes that doesn't even help, since you are still at the mercy of terrestrial repeaters and your antenna placement (antenna placement is more critical with XM than it is with Sirius, as Sirius satellites are more overhead, and XM satellites are more in the southern sky).
While the XM satellites are, the Sirius satellites are not in geosynchronous orbits, and that can cause problems, as well, when the satellite passes temporarily out of view. The Sirius satellites change their position in the sky relative to the earth throughout the day. They have 3 in orbit, so the idea is that even though they sweep over the sky you should have mostly complete coverage all the time. Your signal strength and angel of reception will change though. You can have one tree-lined street that gets very intermittent reception in the morning, but excellent reception in the afternoon.
Also, try unplugging and plugging in the antenna. As well, check the cable wire carefully for any breaks.
And of course, if you haven't, you should do a Refresh of the radio.
- The refresh signal will be sent from a satellite, so make sure your vehicle is outside and your antenna has a clear view of the sky.
- Start your car, turn your radio on and tune to Channel 184 for Sirius radios or Channel 1 for XM and SiriusXM radios.
- You'll need to enter your Radio ID/ESN, so have it handy.
- Click here, enter your Radio ID, and then click Send Activation Request.
- Your refresh signal should reach your radio within 5 minutes.
