The Tech SAM Site is a neutral defensive structure that, when captured by an Engineer, is basically a surface-to-air (SAM) missile site able to engage aircraft effectively.
The Tech SAM Site is technically a capturable Patriot Missile Site, but it requires no power at all (the only stationary anti-air defense that has this attribute), has more hit points and firepower. This makes this defense not as much of a burden as capturing a Tech SAM Bunker.
It is effective against light to medium aircraft; its accuracy and fast projectile speed makes it impossible for such aircraft to dodge its attacks. Only retreating fast aircraft (such as fighter jets) are able to outrun its missiles.