The end-fed half-wave (EFHW) is a half-wavelength wire fed at one end instead of the middle. You feed it at a high-impedance point (~2450 ohms), so it needs a 49:1 unun to match 50-ohm coax — but in return you get a resonant, often multiband wire you can hang as a sloper, inverted-L or straight run with the feedpoint right at the shack.
A half-wave on the lowest band is also a full wave on the next harmonic band, so a single EFHW can cover several bands (for example 40/20/15/10 m) with one feedline and no tuner. Add a short counterpoise on the ground side of the unun, and see the balun and unun guide to wind the 49:1.
| Band | Total wire length | Counterpoise (optional, helps tuning) |
|---|---|---|
| 160m | 74.95 m / 245.9 ft | 7.89 m / 25.9 ft |
| 80m | 37.97 m / 124.6 ft | 4.00 m / 13.1 ft |
| 60m | 26.58 m / 87.2 ft | 2.80 m / 9.2 ft |
| 40m | 20.06 m / 65.8 ft | 2.11 m / 6.9 ft |
| 30m | 14.06 m / 46.1 ft | 1.48 m / 4.9 ft |
| 20m | 10.05 m / 33.0 ft | 1.06 m / 3.5 ft |
| 17m | 7.86 m / 25.8 ft | 0.83 m / 2.7 ft |
| 15m | 6.71 m / 22.0 ft | 0.71 m / 2.3 ft |
| 12m | 5.71 m / 18.7 ft | 0.60 m / 2.0 ft |
| 10m | 5.00 m / 16.4 ft | 0.53 m / 1.7 ft |
| 6m | 2.82 m / 9.3 ft | 0.30 m / 1.0 ft |
Model this antenna interactively → for gain, takeoff angle and azimuth/elevation patterns.
About 20.1 m (66 ft) of wire, a half wavelength on 40 m. That same wire also resonates on 20, 15 and 10 m.
An end-fed half-wave presents roughly 2450 ohms at the feedpoint. A 49:1 unun (7:1 turns, since 7 squared is 49) transforms that down to about 50 ohms for the coax.
It works best with a short counterpoise (about 0.05 wavelengths) on the ground side of the unun. It doesn't need a full radial field like a vertical.
Yes. A half-wave on the lowest band is a full wave on the next harmonic band and so on, so one wire can cover several bands without a tuner.