Subelement B: Transmitting Systems – 8 Key Topics – 8 Exam Questions— Topic 13: Modulation
Question 8-13B1
Element 8 (RADAR)In a solid-state RADAR modulator, the duration of the transmitted pulse is determined by:
Explanation
In a solid-state RADAR modulator, the **Pulse Forming Network (PFN)** is an essential component specifically designed to store electrical energy and then discharge it over a precise, predetermined period. The physical and electrical characteristics of the PFN (such as the length of a transmission line, or the values of its capacitors and inductors) directly dictate the duration of the high-power pulse delivered to the RF amplifier (like a magnetron).
A thyratron (A) is an older, vacuum tube switching device, largely replaced by solid-state components (e.g., SCRs or MOSFETs) in modern modulators; these devices only *switch* the PFN, not determine the pulse width. The magnetron voltage (B) is a *result* of the PFN's output, not the controller of the pulse's length. The trigger pulse (D) merely initiates the PFN's discharge but does not determine its duration.
Related Questions
8-12B5 A negative voltage is commonly applied to the magnetron cathode rather than a positive voltage to the magnetron anode because:8-12B6 The anode of a magnetron is normally maintained at ground potential:8-13B2 The modulation frequency of most RADAR systems is between:8-13B3 A shipboard RADAR uses a PFN driving a magnetron cathode through a step-up transformer. This results in which type of modulation?8-13B4 In a pulse modulated magnetron what device determines the shape and width of the pulse?