Where does operation of any RADAR system begin?

The operation of any RADAR system begins at the triggering section. This part of the radar system is responsible for initiating the radar pulse transmission. It typically generates the pulse that triggers the transmitter, starting the process of emitting radio waves that will later be bounced off targets and received back by the system.

The triggering section plays a crucial role because it sets the timing for the radar's operations, allowing the system to accurately measure the time it takes for the emitted signal to travel to an object and back. This time measurement is fundamental for determining the distance to the target, which is a primary function of radar technology.

The other choices refer to different components or functions within a radar system. The magnetron is a type of oscillator used to generate microwave signals, but it operates after the triggering section. The Automatic Frequency Control (AFC) is utilized to maintain frequency stability, and the Pulse Forming Network (PFN) shapes the pulse used in the transmission, but neither of these functions initiates the radar operation. Thus, the originating point of operation is indeed the triggering section, setting into motion the entire radar functioning sequence.