Ham Radio General Class Practice Test 2025 – Complete Exam Prep

To prevent standing waves on an antenna feed line, it is essential to match the antenna feed-point impedance to the characteristic impedance of the feed line. When these impedances are matched, maximum power transfer occurs, minimizing reflections that create standing waves along the feed line. Standing waves are the result of the interference between forward and reflected waves, and when there's a mismatch, the reflected waves can cause variations in voltage and current along the line, which is visually represented by standing wave patterns.

The characteristic impedance of the feed line is determined by its physical construction and the materials used, while the antenna's feed-point impedance varies based on its design and the frequency of operation. Therefore, ensuring these values are in agreement is crucial in achieving an efficient antenna system and reducing potential performance issues caused by standing waves.

The other options do not directly address the critical issue of impedance matching that is fundamental to preventing standing waves. Grounding at DC potential or cutting the feed line to specific lengths might influence other aspects of performance but do not resolve the root cause of impedance mismatch that leads to standing waves.