I hate to quote Wackipedia - but it is usually a good starting point at least for non-contentious stuff.
http://en.wikipedia.org/wiki/MPQ-64_Sentinel
Your query is about the Sentinel - that is a Hummer-mounted search radar, which is a separate air warning vehicle for all stinger units. It ain't mounted on the M6 Linebacker Bradleys. SP does not model separate AAA search radars or directors. All SP ADA units will auto point at air targets, they do not need to be cued in by a third party.
However - I did notice a few data points in the linebackers that need addressing, on the queue now.
Andy