Subaru WRX STI Owner's Manual page 291

5-36
Audio/Radio operation
The message HD Channel is unavailable appears in the following situations.
Caution Contents
This caution message appears
when the digital reception is not
possible.
I n f o r ma t i o n P r o v i d e d b y :
Case
.
When the system
determined that the SPS
station could not be re-
ceived while receiving a
digital broadcast and SPS
station.
.
When the SPS broadcast
is ended (stopped) by the
radio station while receiv-
ing SPS.
Conditions when caution
disappears
.
When the status is changed
to acquiring digital data
because the reception
condition of SPS station
has improved.
.
When the received station is
changed.