Abstract: A compact selectable AC/DC coaxial coupling having a cylindrical signal coupling capacitor disposed within a section of coaxial transmission line. Inner and outer plates of the capacitor are electrically connected to an external connector and the center conductor of the transmission line, respectively. A radially biased conductive collet or a conductive mesh axially disposed on the center conductor is biased into and out of contact with the inner plate of the capacitor to enable or disable DC coupling. Alternatively, a resilient contact member is displaced through an externally accessible actuating rod to connect the center conductor to the inner plate of the capacitor. The integral nature of these switching mechanisms within a coaxial environment provides both low insertion losses and continuous impedance matching.