Capstan Winch Central to this adjustable all-band dipole antenna
The perfect antenna is the holy grail of amateur radio. Antenna tuning is a game of inches, however, and since the optimal length of an antenna depends on the frequency on which it is used, the mere turning of the dial means that any antenna design is a compromise. Or maybe not if you build this continuously adjustable capstan winch dipole antenna.
Dipoles are generally built to oscillate around the center frequency of a band. Hams are often given a dipole forest in assignments that range almost from “direct current to daylight”. [AD0MZ]The adjustable dipole solves this problem and makes the antenna usable from the 80 meter band up to 10 meters. To accomplish this feat, something familiar is used to every sailor: a winch.
The antenna feed point contains a pair of 3D printed drums, each wrapped with a loop of 18-gauge tin-plated antenna wire attached to a Dacron cable. These form the length-adjustable elements of the antenna, which are tensioned by pulleys that are suspended in trees about 40 meters apart. Inside the Feedpoint case are brushes from an electric drill to connect the elements with a 1: 1 balun and a stepper motor to drive the winch. When the wire loosens from one spool, the dacron cord is picked up by the other. The same thing happens on the other side of the antenna, resulting in a balanced configuration.
We think this is a really clever design that should make a lot of hams in all bands happy. We even see how this can be adapted to other antenna configurations, like the end-fed half-wave we recently featured in our “$ 50 Ham” series.