Hat day, bobblehead day, umbrella day -- the usual baseball promotions might seem a little blah after Saturday, when XM Satellite Radio Holdings Inc. plans to give an XM-compatible radio to every ticketholder who enters Chicago's U.S. Cellular Field for the first game of the World Series.

Every fan at the 40,000-seat venue will receive a coupon for the Delphi XM RoadyXT satellite radio, which retails for $79.99, company spokesman David Butler said. XM will make the same offer to fans at Minute Maid Park in Houston, if the World Series makes it to a fifth game.

There is a catch, however: Those baseball fans will have to prepay for at least three months' worth of the $12.95-a-month service if they want to get any use out of the flashy gadget. (The company also is giving out commemorative pins, which will come with no subscription fees attached.)

World Series-attending baseball fans are a natural target for XM, as the service has exclusive satellite radio rights to broadcast Major League Baseball games.

XM says its subscriber base doubled to more than 5 million in the year since October 2004, when the company announced that it would carry the games. In a recent customer survey, 23 percent of those new subscribers said they chose XM because of the baseball programming.

Sports fans represent just one playing field for a company trying to win subscribers. The Washington-based satellite radio service recently announced a deal with Honda to install XM receivers in 550,000 vehicles for the 2006 model year, including Civics, Accords and Accord Hybrids.

XM spokesman Butler said that about 60 percent of new car buyers subscribe to the service when an XM unit comes installed. He said he was not sure what sort of take-up rate the company expects with the giveaway.

New-car owners typically get a free trial period in which to check out the XM radio service; baseball fans who get a free XM radio at the Saturday game will not, though the satellite radio service will waive activation fees for those units. XM users get access to 150 channels of music, talk, news and sports.

XM competitor Sirius says it has 1.8 million subscribers, a figure that may jump when radio host Howard Stern moves to the service in January.

Fans at the first and fifth games of the World Series will receive a coupon for a Delphi XM RoadyXT radio from XM Satellite Radio Holdings Inc.