I don't believe XTS 3Ks can do Channel Announcements.
XTS 5000s need to have option Q446 in the flashcode to be able to do CA:
Once you make sure you have Q446 you then have to jump through a lot of hurdles to make the CA feature work:
1) Make sure you go to Radio Wide->General->then select Channel Announcement.
2) Create the CA file and convert it to Wav format.
3) Make sure it fits the following requirements:
4) Once the wav file fits the above requirements then hook a fully charged XTS 5000 up to your computer and Go to Tools->Voice Files->Voice Files Compression and let CPS convert the wav files to Motorola XTS "mvf" format then select a folder where to save them.
5) Now you still have to go to File->import->Voice file and import the mvf CA files into CPS.
6) Do note that the more CA Voice Files you load into your XTS radio the slower the radio will operate when changing channels, zones, etc. You try to load CA files into every zone your radio will quickly become an unusable brick.
Be conservative about where you use CA files and how many you assign.
My suspicion has always been that Motorola made it extremely difficult to create & load CA files on purpose because they hate them.
Marshall KE4ZNR