Question 6A514

Harmonic radiation, unwanted multiples of the fundamental operating frequency, can be effectively suppressed by employing multiple techniques. Suitable tuned filters, typically low-pass filters, installed in the transmission line system between the final amplifier and the antenna, are designed to pass the desired fundamental frequency while strongly attenuating higher frequencies, including harmonics. This directly blocks harmonics from reaching the antenna. A Faraday shield, when incorporated in matching transformers or baluns, acts as an electrostatic screen between windings. It significantly reduces capacitive coupling. Since harmonics can be capacitively coupled from the amplifier's output stage to the antenna system, a Faraday shield breaks this path, preventing those harmonics from being radiated. Option A, using a crystal filter, is primarily for selecting a specific fundamental frequency within the exciter stages or for receiver selectivity, not for high-power output harmonic suppression. Therefore, both a Faraday shield and tuned filters provide distinct yet complementary methods for preventing harmonic radiation.