Sirius XM RAdio XM Onyx User Manual page 24

Vehicle Installation
CAUTION! Don't mount the antenna inside
the vehicle, for example, on the dashboard.
CAUTION! Don't mount the antenna on any
of the vehicle's front, back or side pillars.
CAUTION! Don't mount the antenna close
to a roof rack. Adjust the rack so it's further
away from the antenna or move the antenna
closer to the center of the roof.
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