These are the Fire control radars (FCR) for the enemy team. They provide targeting and launch authorization to SAM launchers. At least one FCR is needed for a sam battery to fire. The allies have the Fire Ctrl Radar P which is basically Fire Control Radar 1 with a different model.
Fire Control Radar 1
This unit is a phased-array radar. It has a lateral scan angle of 120 degrees, and can scan from parallel to its base to straight up 90 degrees. It has a fast scan rate which is audible on the RWR as pings more frequent than the Fire Control Radar 2.
Fire Control Radar 2
This unit uses a rotating dish radar. It can scan vertically from the ground up to (?) degrees. Laterally, the dish sends out a a vertical fan that sweeps clockwise when viewed from the top down. Because the dish has to make a full rotation, the update cycles and RWR pings are much slower.
Usage and Configuration
SAM launchers are configured in the mission editor to link up to at least one radar site. Several radar sites provide redundancy to authorize launches. SAM batteries have ranges much smaller than the radar can see, so spreading out launch sites increase the odds that one is close enough to a detected aircraft to launch. Otherwise, a detected aircraft may be able to use standoff weapon to stay out of range of any launcher.