Abstract: An antenna diversity switch for IFF radar equipment not having such a switch incorporated in it. This new diversity switch requires no modification of the existing IFF components. The blanking pulses generated by the IFF system when an interrogating signal is received are used to trigger a monostable multivibrator which stops a free-running flip-flop controlling the switching between two antennas so that the antenna connected at that time remains connected. When the blanking pulses stop, i.e., the interrogating signal is too weak to be received, the monostable multivibrator is returned to its untriggered condition which allows the flip-flop and its controlled antenna switch to resume switching between the antennas. Suitable timing controls are provided to switch antennas at the desired rate and to keep the diversity switch connected to a receiving antenna for a desired delay time after the received interrogating signal ceases.