An end-fed random wire is a non-resonant wire fed through a 9:1 unun and an antenna tuner — one of the simplest multiband antennas you can put up. But the length isn't truly random: you want it long enough to radiate on your lowest band and chosen to avoid half-wave resonances, where the impedance rockets too high for the unun and tuner to match.
Shorter wires aren't effective on the low bands — a wire that's a fine radiator on 20 m is an inefficient stub on 80 m. The table below shows the shortest wire we'd recommend for each lowest band. Always run a counterpoise from the unun's ground side, and see the balun and unun guide to wind the 9:1.
| Lowest band you want | Recommended wire length |
|---|---|
| 160m and up | 92.9 m / 305 ft |
| 80m and up | 51.0 m / 167 ft |
| 40m and up | 37.7 m / 124 ft |
| 20m and up | 13.0 m / 43 ft |
Model this antenna interactively → for gain, takeoff angle and azimuth/elevation patterns.
Long enough to be at least about a third of a wavelength on your lowest band, and clear of half-wave multiples on the bands you use. See the chart above for a recommended length per lowest band.
Yes. A non-resonant end-fed wire needs something to work against, so run one or more counterpoise wires (or a few radials) from the ground side of the 9:1 unun.
A 9:1 unun is for non-resonant random wires (around 450 ohms); a 49:1 is for resonant end-fed half-waves (around 2450 ohms). They are not interchangeable.
At a half wavelength and its multiples an end-fed wire's impedance is very high, thousands of ohms, which a 9:1 unun and tuner can't bring to a usable match. Good random-wire lengths steer clear of those points.