An antenna tuner, for amateur radio.

An antenna tuner, or transmatch, is a useful item for matching the impedance of an antenna system to the impedance desired by the output section of a radio transmitter.

They are simple items to make, and since I had a metal box and two variable capacitors, all I needed to do was wind a coil. The regular spacing of the windings over the PVC pipe was set over the plastic section of a header terminal strip after removing the metal pins.