Which unit receives the reference sweep signal from the synchronizer?

The reference sweep signal is a critical component in radar systems, primarily used to synchronize the timing of the radar's operation. In this case, the antenna is responsible for transmitting and receiving radar signals, as well as ensuring that the timing of these signals aligns perfectly with the radar's operations.

The synchronizer generates the reference sweep signal to establish a consistent timing framework for the radar system. This signal is crucial for coordinating the various components of the radar, ensuring that data captured by the antenna can be accurately processed and interpreted. The antenna directly relies on this signal for its operational timing, allowing it to perform its functions of emitting and receiving radio waves effectively.

Other components like the processing unit, display unit, and data recorder usually rely on input from the antenna to function correctly. While they play important roles in processing, displaying, or recording the radar data, they are not the immediate recipients of the reference sweep signal from the synchronizer. The direct connection and dependency of the antenna on this timing signal make it the correct answer.