GMC Sierra Denali Classic 2007 Owner's Manual page 215

BAND (Alternate Frequency): Alternate
frequency allows the radio to switch to a stronger
station with the same program type. To turn
alternate frequency on, press and hold BAND for
two seconds. AF ON will appear on the display.
The radio may switch to stations with a stronger
frequency.
To turn alternate frequency off, press and hold
BAND again for two seconds. AF OFF will appear
on the display. The radio will not switch to
other stations.
This function does not apply for XM™ Satellite
Radio Service.
Setting Preset PTYs (RDS Only)
These buttons have factory PTY presets. Up to
12 PTYs (six FM1 and six FM2), can be
programmed on the six numbered pushbuttons, by
performing the following steps:
1. Press BAND to select FM1 or FM2.
2. Press the TYPE button to activate program
type select mode. TYPE and the last selected
PTY will appear on the display.
3. Turn the TYPE knob or press and release the
TYPE button to select a PTY.
4. Press and hold one of the six numbered
pushbuttons until you hear a beep.
Whenever that numbered pushbutton is
pressed, the PTY that was set will return.
5. Repeat the steps for each pushbutton.
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