Question 8-47F4

A high Voltage Standing Wave Ratio (VSWR) indicates a significant impedance mismatch in the transmission line, causing a large portion of the transmitted power to reflect back towards the source. The signal path in a marine RADAR system goes from the magnetron, through the waveguide, the rotary joint, and finally to the antenna array, which radiates the energy into space. The antenna array effectively acts as the termination (load) for the entire transmission line system. If the waveguide and rotary joint are functioning properly, the impedance mismatch causing the high VSWR must be occurring further down the line. A malfunctioning or damaged waveguide array (the antenna itself) would present an improper load impedance, preventing efficient radiation of power and causing reflections. This reflected power would then be measured as high VSWR at the magnetron output. * **A) The magnetron:** While a faulty magnetron can cause power output issues, it's not typically the direct cause of high VSWR due to a load mismatch. * **B) The waveform generator:** This circuit controls the timing and pulse width of the radar signal and does not affect the transmission line's impedance match. * **C) The STC circuit:** Sensitivity Time Control is a receiver function that adjusts gain to compensate for signal strength changes with range; it is unrelated to the transmit path's impedance.