Which component or network primarily determines the impedance match between feedline and antenna across the operating band?

• A. The transmitter output impedance
• B. The feedline gauge
• C. The matching network and antenna impedance
• D. The receiver input impedance

Answer: (C)

The thing that sets how well the feedline and antenna are matched across the band is the combination of the antenna’s input impedance and the matching network that connects to it. The antenna presents an impedance that generally varies with frequency and mounting conditions. A matching network (which can be a dedicated antenna tuner or the antenna’s own built-in sizing and loading) transforms that complex impedance so it looks like the feedline’s characteristic impedance (often 50 ohms) over the operating range. When this transformation is done effectively, power transfer is maximized and reflections are minimized across the band.

Transmitter output impedance is part of the overall system design, but it isn’t what establishes the match across frequencies—the matching network and the antenna impedance do. The feedline gauge mainly affects losses and current capability rather than setting the impedance seen at the feedpoint. The receiver input impedance matters for receiving, but the forward-path match between feedline and antenna is governed by the antenna impedance and its matching network.