ll times. Sirius completed its three-satellite constellation on November 30, 2000. A fourth satellite will remain on the ground, ready to be launched if any of the three active satellites encounter transmission problems. (http://www.siriusradio.com/servlet/snav?/servlet/about/se_work.jsp) The Sirius system is similar to that of XM. Programs will be beamed to one of the three Sirius satellites, which will then transmit the signal to the ground, where your radio receiver will pick up one of the channels within the signal. Signals will also be beamed to ground repeaters for listeners in urban areas where the satellite signal can be interrupted. While XM offers both car and portable radios, Sirius is concentrating solely on the car radio market. The Sirius receiver will include two parts, the antenna module and the receiver module. The antenna module will pick up signals from the ground repeaters or the satellite, amplify the signal and filter out any interference. The signal will then be passed on to the receiver module. Inside the receiver module will be a chipset consisting of eight chips. The chipset will convert the signals from 2.3 gigahertz (GHz) to a lower intermediate frequency. Sirius will also offer an adapter that will allow conventional car radios to receive satellite signals. The adapter will cost about $199. WorldSpace So far, WorldSpace has been the leader in the satellite radio industry. It put two of its three satellites, AfriStar and AsiaStar, in geostationary orbit before either of the other two companies launched one. AfriStar and AsiaStar were launched in October 1998 and March 2000 respectively. AmeriStar is currently scheduled for launch in late 2001. Each satellite transmits three signal beams, carrying more than 40 channels of programming, to three overlapping coverage areas of about 5.4 million square miles (14 million square km) each. Each of the WorldSpace satellites' three beams can deli...
