End-fed wires, loops and random wires

Not every lot supports a centre-fed dipole. These are the alternatives people actually put up, and what each one demands in return.

End-fed half-wave (EFHW)

A half-wave wire fed at one end, where the impedance is very high (2,000–4,000 Ω), through a 49:1 or 64:1 unun.

• One support at each end, and the feedpoint can be at the house — the main reason it dominates

portable operating.

• A half-wave on 40 m is also a full wave on 20 m and so on, so a single 66-foot wire covers 40,

20, 15 and 10 m with a small tuner smoothing the edges.

• The coax braid is part of the antenna's counterpoise. Fit a common-mode choke a quarter

wavelength down the feedline, or you will find RF in the shack.

• Add a short counterpoise (about 0.05 λ) at the transformer; performance improves noticeably.

Random wire with a 9:1 unun

Any convenient length of wire, a 9:1 unun and a tuner.

• Genuinely multiband, and the least fussy thing to erect.
• Avoid lengths near a half wave on any band you use, and avoid 32, 64 and 96 feet.
• Efficiency depends entirely on the radial or counterpoise system; a single wire on the ground is

the difference between "works" and "works well".

• Some loss is unavoidable — this is a compromise antenna, and it still makes contacts worldwide.

Full-wave loops

A closed loop, one wavelength around, fed with coax and a 4:1 balun (or open-wire line and a tuner).

• Roughly 1–2 dB of gain over a dipole, and noticeably quieter on receive — the usual reason people

build them.

• Horizontal at low height: a superb NVIS antenna for regional

emergency nets. Vertical: lower angle and useful for DX.

• Length in feet ≈ 1005 / frequency in MHz. Shape matters much less than getting it up.

Magnetic loops

A small tuned loop, typically 3 to 6 feet across, with a high-Q variable capacitor.

• Works indoors, on a balcony, or on a small patio — often the only option under an

HOA.

• Very narrow bandwidth: retune for every few kHz.
• Extremely high RF voltages at the capacitor. Do not touch it while transmitting, and keep it out

of reach.

• Efficiency falls sharply on the low bands, but 20 m and up can be surprisingly good.

Off-centre-fed and doublets

• OCF (Windom) — fed about a third of the way along, 4:1 or 6:1 balun, several bands from one

wire. Common-mode current is its weak point; choke it well.

• Doublet — any length of wire, centre-fed with open-wire or ladder line into a balanced tuner.

Loss stays low even at high SWR, which makes it the most efficient truly multiband antenna, at the cost of needing the line to run clear of metal.

The common thread

All of these are compromises against a resonant dipole in the clear. Get the wire high, keep it away from gutters and wiring, choke the common-mode current, and none of the compromises will matter as much as the height did.