The XM Satellite Radio system from Radio-at-Sea brings 70 channels of digital music, news, sports and entertainment to the sound systems of boats. The system uses a high-gain marine antenna and Audiovox receiver to receive the satellite signal on inland waterways or hundreds of miles off the coast of the continental U.S. The satellites are located at 85 ¿ and 105 ¿ west longitude and transmit a signal operating at 2.3 GHz, which makes the signal relatively insensitive to moisture attenuation due to rain and fog. The complete Radio-at-Sea system sells for $595 and the subscription fee for the programming is $9.99 per month. Radio-at-Sea, Pembroke, MA; (800) 556-3911; www.radio-at-sea.com.