Summer’s coming up and that means lots of us will be taking long trips in our cars.  That also means that we have to get together some entertainment:  Our CDs or, heaven forbid, the old cassettes. Well, that also poses the problem of having to change them repeatedly to keep things fresh. Well,  now there is an answer. It’s Digital Audio Radio Service, or Satellite Radio.

Actually, I should say that there are two options, since there are two different companies now offering satellite radio: XM and Sirius.  As the name suggests, these systems use space- orbiting satellites to transmit digital-quality music and news programming coast-to-coast to cars and homes equipped with special receivers. They work just like Satellite TV. Subscribers pay a monthly fee for the service and can choose from up to a hundred stations on each service offering niche programming for all kinds of musical tastes.

On XM, for instance, listeners can choose from six jazz channels, three comedy channels, five channels of Latin music or others dedicated to kids, news, sports and so on. XM broadcasts from its Washington, D.C. headquarters, where it has 82 all-digital studios for DJs as well as a large studio for live performances.  The XM system uses two satellites, named ‘‘Rock’’ and ‘‘Roll’’ in a geostationary orbit over North America, making it technically easier to lock on to their signal.

Sirius uses three satellites that move in a pattern, meaning their signal has to be tracked.  But they beam from a higher angle, so there is less chance of having the signal blocked, like by tall buildings for instance.

Major car makers like Ford, Chrysler, GM, VW and Nissan have already signed on to offer one or both systems as factory options, and Sony has an XM home adapter that allows you to experience the system whether you’re on the road or just on the sofa.

Picking one system over another is not as risky as choosing between VHS and Betamax was twenty years ago.  Both XM and Sirius have similar types of programming and substantial commitments from OEMs and the aftermarket. The cost is about the same: XM at $10 a month and Sirius at $12.  I would give a slight edge right now to XM in terms of name recognition and market coverage, but Sirius is determined to catch up fast.

Satellite radio can take some of the stress out of your trip, but remember before you leave, have your car checked mechanically to be sure that it’s safe.  If you have a question or a comment, write to me.  If I use your letter, I’ll send you a MotorWeek T-shirt.  The address is MotorWeek, Owings Mills, MD, 21117.