Chevrolet Tahoe Owner's Manual page 209

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 the radio.
FM signals only reach about
16 to 65 km (10 to 40 mi). Although
the radio has a built-in electronic
circuit that automatically works to
reduce interference, some static can
occur, especially around tall
buildings or hills, causing the sound
to fade in and out.
SiriusXM 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 tunnels may cause loss
of the SiriusXM signal for a period
of time.
Cellular phone usage may cause
interference with the vehicle's radio.
This interference may occur when
making or receiving phone calls,
charging the phone's battery,
or simply having the phone on. This
interference causes an increased
level of static while listening to the
radio. If static is received while
listening to the radio, unplug the
cellular phone and turn it off.
The AM-FM antenna is located in
the passenger rear side windows.
Make sure the inside surfaces of the
rear side windows are not scratched
and that the lines on the glass are
not damaged. If the inside surfaces
are damaged, they could interfere
with radio reception.
If a cellular telephone antenna
needs to be attached to the glass,
make sure that the grid lines for the
AM-FM antenna are not damaged.
There is enough space between the
grid lines to attach a cellular
telephone antenna without
interfering with radio reception.