GMC 2008 Acadia - Manual (Page 271)

Radio Reception
Frequency interference and static can occur during
normal radio reception if items such as cell phone
chargers, vehicle convenience accessories, and external
electronic devices are plugged into the accessory
power outlet. If there is interference or static, unplug
the item from the accessory power outlet.
AM
The range for most AM stations is greater than for
FM, especially at night. The longer range can cause
station frequencies to interfere with each other.
For better radio reception, most AM radio stations
boost the power levels during the day, and then reduce
these levels during the night. Static can also occur
when things like storms and power lines interfere
with radio reception. When this happens, try reducing
the treble on your radio.
FM Stereo
FM stereo gives the best sound, but FM signals only
reach about 10 to 40 miles (16 to 65 km). Tall buildings
or hills can interfere with FM signals, causing the
sound to fade in and out.
XM™ Satellite Radio Service
XM™ Satellite Radio Service gives digital radio
reception from coast-to-coast in the 48 contiguous
United States, and in Canada. Just as with FM,
tall buildings or hills can interfere with satellite radio
signals, causing the sound to fade in and out. In
addition, traveling or standing under heavy foliage,
bridges, garages, or through tunnels could cause loss
of the XM signal for a period of time. The radio may
display NO XM SIGNAL to indicate interference.
Multi-Band Antenna
The multi-band antenna is located on the roof of your
vehicle. This type of antenna is used with the AM/FM
radio, as well as OnStar
® and the XM™ Satellite Radio
Service System, if your vehicle has these features.
Keep this antenna clear of snow and ice build up for
clear radio reception. If your vehicle has a sunroof,
the performance of the radio system may be affected if
the sunroof is open. Loading items onto the roof of
your vehicle can interfere with the performance of the
radio system and, if your vehicle has this feature,
OnStar
® . Make sure the multi-band antenna is not
obstructed.
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