Which radar component prevents RF energy from directing into the receiver during transmission?

The correct answer identifies the duplexer as the component that prevents RF (radio frequency) energy from reaching the receiver during the transmission phase of radar operation. In radar systems, the transmitter sends out RF signals, which can be harmful to the sensitive receiver if they were to be directed into it at the same time. The duplexer acts as a switch that allows the radar system to alternate between transmitting and receiving modes.

When the transmitter is active, the duplexer ensures that the RF energy is directed exclusively to the antenna for transmission, thereby protecting the receiver from being overloaded by its own emitted signals. When the transmission is complete and the system switches to receive mode, the duplexer changes the pathway, allowing incoming signals to flow into the receiver while ensuring that no transmission energy interferes with the reception process.

Other components like the modulator, receiver, and transmitter play critical roles in the radar system but do not specifically handle the switching of RF energy between transmission and reception phases. Therefore, the duplexer's unique function is paramount for protecting the radar's receiver during operation.