All it takes is one trip, whether 150 miles or 1,500 miles, to appreciate how wonderful it is when radio stations do not fade in and out and you do not have to search for a new station every half hour or so. It always seems to happen when you get to the most interesting part of the program. And retuning a radio is one of the leading distractions causing accidents, according to the National Transportation Safety Board. Satellite radio virtually eliminates the need to change stations.

Only two companies – XM Satellite Radio and Sirius Satellite Radio – provide the service. XM started broadcasting in late 2001 and is now nationwide, while Sirius began in February and expects to complete nationwide coverage this summer. Each has its own satellite network, electronic circuitry and programming.

XM uses two satellites, nicknamed “Rock” and “Roll,” in stationary orbits 22,300 miles above the Equator. One covers the East Coast, the other covers the West Coast. XM claims its system makes it easier to keep its uplinks on target, providing more accurate, more reliable digital transmissions.

Sirius uses three satellites, orbiting in elliptical figure-8 patterns above the United States. Sirius claims that with its satellites orbiting more nearly vertically over the U.S., there is less shadowing from tall buildings and canyons, and that at least two satellites are available at any time.

Both systems require line-of-sight transmission, and have repeaters in large cities or areas where reception would be interrupted.

XM and Sirius operate on different frequencies and use slightly different technology, so the receivers and antennas are not interchangeable. There has been discussion of building receivers capable of accessing either or both systems, as is the case with AM and FM, but that would be in the future.

While some XM music programming is original, XM also rebroadcasts some of the commercial stations you can receive on FM and AM bands. Sirius has no commercial stations on its network – meaning all of its music programming is original.

Both services provide radio versions of popular news, weather and sports programming such as CNN, Headline News, ESPN, ABC News and Talk and C-Span. XM has Fox News and is exclusive with the NASCAR Channel. Sirius has the Speed Channel, the Outdoor Life Network, A&E and two NPR channels.

Each service has its own truckers’ channel. XM has Bill Mack and the Truckin’ Bozo, live at night and rebroadcast during the day. Sirius has Eric Harley and the Midnight Trucking Radio Network. Truckers radio programming repeats and around the clock.

The concept appears to be catching on among truckers as prices for receivers fall and truckstops such as TA offer sales, installation and activation. XM also won the Truck Writers of North America Technical Achievement Award for 2001.

Paul Abelson tested XM when it debuted and now owns a receiver, while Tony Dolle tested a Sirius unit when the service began in Nashville in May. Here are their comments:

XM

I have a Delco XM adapter from Delphi Electronics. It has a box for the electronics about the size of a VCR cassette, and a tuner with five pre-sets in each of two bands, plus channel-up and channel-down buttons. At the touch of another button, program information appears on the LCD face of the 6-by-2-by-1-3/4-inch dash-top control module. The electronics box is hidden.

My XM receiver has a buffer to prevent signal loss in short tunnels and underpasses or when passing the north side of tall buildings. The satellite broadcasts each station’s signal twice, with a four-second delay between them. The first signal goes into memory while the second is played live.

Whenever the second signal is interrupted, the XM receiver seamlessly switches to the signal in memory. Since it takes less than four seconds to pass through most underpasses, even at city speeds, there are almost never any breaks in what you hear. The only times I lost service were when I parked nose-in on the north side of a tall building or when I went into some garage buildings.

XM provides various compilations of music, put together in its own studios. Among its 30 commercial-free music channels are dedicated jazz, blues, rock, Latin and classical music stations.

Channels 4 through 9 cover decades from the ’40s through the ’90s. Country music fans have six channels, from classic country to bluegrass and traditional (Hank Williams’ era) to progressive. Urban, rock, dance, Latin and world music each have a group of from four to 10 channels, with another 15 for popular hits.

There are three comedy channels, two for kids, five sports channels, 12 news channels and nine covering a variety of programming from entertainment (TV’s “E!”) to the Discovery Channel. Classical music lovers can select channels offering opera, traditional and classical “hits.”

Generally, XM receivers that play through your existing FM radio run as low as $199. Antennas start at $80 for low-profile models, while 4-foot mirror-mounted masts cost up to $175. Installation costs extra, although many retailers offer free “basic” installation as a promotion. That may not include truck installations. The monthly service fee for XM is $9.99.

TravelCenters of America now offers sales, installation and activation of some models of XM receivers and antennas.

Sirius

Sirius says it always has two satellites orbiting over the U.S., which provides higher angles for reception. Sirius says this enhances its ability to provide service in downtown areas where tall buildings often block other radio signals and in mountainous areas where the peaks and canyon walls do the same.

Music selections on Sirius include: Top 40 pop, music from the decades from the ’50s to the ’90s, special all-pop mix channels and love songs;

Eleven rock channels from soft, modern and classic rock to left of center, hard rock, and alternative rock;

Six country music channels, from the new hits to bluegrass, alternative and classics;

Eight channels of jazz, R&B, rap, hip-hop, soul and four channels of dance hits from just about every era of popular music.

Habla Espańol? Even if you don’t speak the language, Sirius offers full-flavored Latin music. There are also three channels for classical chamber works, symphonies and voice selections. There are also Sci-Fi, comedy, radio classics, entertainment news and even Disney and Discovery radio channels. As this is written, Sirius is in negotiations with TA to offer sales, installation and activation at its travel centers. But you can get a subscription on-line at www.siriusradio.com or through Crutchfield catalogs or Circuit City, Best Buy or similar retail outlets.

Major electronics manufacturers are building their radios to handle satellite radio reception. Kenwood, Clarion, Panasonic, Sony and others all manufacture Sirius-ready radios; Delphi plans to offer them shortly. Consumer units start at $169 and can go to more than $1,000. The monthly fee for Sirius is $12.95.