How cell towers can block satellite radio signals

Q: I have a SiriusXM satellite radio in my car, but the signal consistently cuts out in specific areas around the Twin Cities. For example, the signal cuts out at the intersections of County Road 42 and Hwy. 5 in Burnsville; Hwy. 101 and Hwy. 13 in Shakopee, and Hwy. 169 and Anderson Lakes Parkway in Bloomington. I've read that the problem could be related to the satellite radio's antenna or to interference from T-Mobile cellular towers. Is there a solution?

Tim Risdal, Burnsville

A: Not yet. SiriusXM Radio and T-Mobile USA acknowledged in late 2015 that T-Mobile cell towers were causing signal interference on SiriusXM's satellite radios. Both companies said fixing the problem was the other firm's responsibility (see tinyurl.com/gq36e2k). So far, neither company has announced a solution. When I sought comment last week, neither responded.

Previously, both companies said that the interference problem is caused by a radio signal phenomenon called "intermodulation." Two different T-Mobile tower frequencies are colliding, thereby creating a third frequency. It is this third radio frequency signal that produces interference on SiriusXM radios.

While there's no way to prove that your loss of a SiriusXM signal is caused by cell tower interference, the locations you mention are near T-Mobile cell towers, according to the website cellreception.com. In Burnsville, the intersection is about 3.5 miles from a tower, in Shakopee about 2 miles away and in Bloomington about 1.5 miles away. Cell tower transmissions can reach up to 10 miles, and directional antennas can be "aimed" toward high-demand areas such as busy highways.

Potential solutions mentioned in 2015 included altering the way the cell towers operate, improving the way satellite radios filter out unrelated signals, or strengthening satellite signals (to overcome interference) by rebroadcasting them from ground stations.

Q: I've previously used Windows System Restore to fix problems on different PCs; it restores a PC's settings to the way they were on a previous date. But I recently discovered that my Windows 7 laptop doesn't have System Restore turned on. I get the message: "System restore has been turned off by your system administrator. To turn on, contact your system administrator." What can I do?

A: Windows System Restore should be turned on default. If it's not on, go to Start and type "system restore" in the search box. In the resulting list, click on "create a restore point." You'll then see a list of "protection settings." Your PC's "C" drive should be listed, and, just to the right of it should be the word "off." Click on the C drive to highlight it, then click on the "configure" button just below the list. In the next menu, check the box next to "turn on system protection."

Below that, under the heading "disk space usage," move the slider control until it says 5 percent. That's the portion of your C disk that will be set aside for "restore points."

If that doesn't work, try using the PC's Group Policy Editor or Registry Editor (see tinyurl.com/zsxlkze). Be careful with the latter; mistakes in the registry can be serious.