Note
The 180S-1 was a pi-network antenna tuner that could be used in either a pi or L configuration.It contained a roller inductor, a vacuum variable capacitor, and an air variable capacitor. It was originally an A-line accessory that hung on through the S/Line era. The 180S-1 matched a variety of antenna impedances to 50 ohm transmitters in the 3–30 MHz range.