In ATCRBS/SSR, the beacon antenna is mounted so it rotates with the surveillance antenna.

• A. True
• B. False
• C. It rotates independently
• D. It is fixed

Answer: (A)

In ATCRBS/SSR, the system relies on a rotating directional beam to interrogate aircraft and then receive their replies. The beacon antenna is mounted to rotate with the surveillance antenna so the direction of the received signal stays aligned with the direction in which the ground station is actively interrogating. This shared rotation lets the system know the bearing of the responding transponder at the moment of interrogation and keeps the transmit and receive paths consistently pointed together. If the beacon antenna rotated independently or remained fixed, the relationship between where the interrogation is sent and where the receiver is most sensitive would be lost, making bearing information unreliable and complicating detection.