The Basic lessons · Feedlines and antenna systems · B-006-006

Matching Antennas and Feedlines for Maximum Power

Learn why radio transmitters reduce power when antennas don't match and how tuners fix this. Discover the rules for moving power efficiently and the best places to install matching devices.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-006-006.

What this subsection asks

• Which of the following antenna system conditions will cause a modern solid-state HF transceiver to automatically reduce power?
• What does an antenna tuner do?
• An end-fed half-wave antenna (EFHW) has a very high feed point impedance. What device could be used to provide a good match to 50-ohm coaxial cable?
• If both source and load impedances are purely resistive, what value of load impedance will result in maximum power delivery to the load?
• What is the advantage of locating an antenna tuner near the antenna feed point, over locating it near the transceiver?
• How does an antenna tuner compensate for an impedance mismatch in an antenna system?
• What advantage does a transformer present when used for impedance matching at radio frequencies?
• Where does impedance matching need to be done to minimize transmission line losses in an antenna system?
• If an antenna is correctly matched to a transmission line, the length of the transmission line:
• Why is an antenna tuner (external or internal) frequently used with modern solid-state transceivers?
• If a transmission line with a characteristic impedance of 50 ohms feeds a folded dipole with a feed point impedance close to 300 ohms, what impedance transformation ratio is needed to match the two?