GM Service Manual Online
For 1990-2009 cars only

Diversity Antenna System

Standard on this vehicle is a diversity antenna system designed to deliver the best radio signal reception possible. Two antennas are used to form a diversity system. The primary antenna attaches to the rear lift window similar to a defogger grid. This antenna receives both AM and FM signals. The secondary antenna is attached to the windshield in the same manner as the primary antenna. This antenna receives only FM (diversity) signals. The antenna reception signals are sorted by a reception processing module and the clearest, strongest signal is constantly fed to the radio control.

Signal Flutter

Multipath or signal flutter is the quickly fading in and out of FM radio signal reception. Multipath or signal flutter most often occurs in downtown areas or wherever large obstructions are present. A radio signal reflects off of buildings at various angles. When one signal crosses paths with a same signal (at a different angle) they will cancel each other out. The signal will be received and then not received very rapidly by a vehicle audio system. This causes a fluttering effect to be heard through a vehicle speakers. With the diversity antenna system one of the two antennas will virtually always receive a strong signal and widely limit mutipath.

AM Mode

The range of most amplitude modulation (AM) stations is greater than FM stations. This is especially true at night. The AM band tuning range is 530 kHz to 1710 kHz.

FM Mode

The frequency modulation (FM) stereo mode has better sound than the AM mode. The reception of the FM stereo signals is usually limited in distance to 16-64 km (10-40 miles) depending on station power, antenna operation, and terrain. Signal flutter or noise can be caused by tall buildings, hills, or other large objects. This can be eliminated by tuning to a stronger station. The FM band tuning range is 87.7 MHz to 107.9 MHz. An FM stereo broadcast is being received when ST is illuminated on the radio display.