Your antenna tuner does not have a balanced output and you wish to use window line to feed an HF antenna. What device should you use between the tuner and the transmission line?

An antenna tuner typically has an unbalanced output designed for coaxial cable, while window line is a balanced transmission line. To connect these two safely and efficiently, you must use a device that converts between balanced and unbalanced systems. This device is called a 'balun', which is a portmanteau of 'balanced to unbalanced'. It ensures that the RF currents on the balanced line remain equal and opposite, preventing the transmission line itself from radiating. Other options like quarter-wave transformers or transmission line stubs are used strictly for impedance matching, not for converting a single-ended, unbalanced feed to a balanced one.