Ham Radio General Class Test 2026 – 400 Free Practice Questions to Pass the Exam

The impedance of a low-pass filter should be about the same as the impedance of the transmission line into which it is inserted to ensure optimal power transfer and minimize signal reflection. When the impedances match, the filter will provide the intended filtering characteristics without causing significant signal loss or distortion. This matching of impedances helps maintain the integrity of the signal as it passes through the filter and into the transmission line.

If the filter's impedance were substantially higher or lower than that of the transmission line, it could lead to reflections at the junction, which would degrade the performance of the entire circuit. This reflection occurs because of the mismatch, causing part of the signal to be reflected back toward the source, which can result in interference, standing waves, or reduced signal strength. Therefore, maintaining an impedance close to that of the transmission line is vital for effective operation.