The SA-19's missiles are guided by optics I think? It has a radar which it uses rarely I'm assuming for better target acquisition. After reading Wikipedia it appears that an optical solution can be used as a back-up. The missile is guided optically, so the missile can only track in a lag pursuit. Missile plume is also super super super bare, so spotting missiles trails to see where it's firing from is nearly impossible. My advise would be to stay high in an enemy's AO and when low just keep turning, the missile isn't very good at hitting maneuvering targets.