The end-fed half-wave (EFHW) antenna has become one of the most popular HF antenna choices for home stations and portable operators alike — and for good reason. A properly set-up EFHW is simple to deploy, works on multiple harmonic bands without a tuner, and can be installed in a variety of configurations: sloped, inverted-V, L-shaped around a corner, or strung up a tree for a POTA activation. Here's how to set one up correctly.
Why the EFHW is so popular: One wire. One end at the radio. Works on 40m, 20m, 15m, and 10m simultaneously (with a 49:1 matching transformer). Low-angle radiation on HF. Easy to deploy in odd yard shapes. Hard to argue with.
How an EFHW Works
A half-wave antenna fed at its end presents a very high impedance at the feedpoint — typically 2,500–5,000 ohms. Standard coax is 50 ohms. A 49:1 matching transformer (also called an UNUN — unbalanced to unbalanced) steps the impedance down to roughly 50 ohms, making it compatible with your transceiver and coax feedline. The transformer is usually a small weatherproof box that mounts at the base of the wire.
On harmonic bands (a 40m EFHW also resonates on 20m, 15m, and 10m), SWR will typically be under 2:1 with no tuner required. On non-harmonic bands like 30m, 17m, and 12m, you'll need a tuner.
Wire Lengths
| Fundamental Band | Wire Length (feet) | Wire Length (meters) | Also Resonant On |
|---|---|---|---|
| 80m | ~130 ft | ~39.6 m | 40m, 20m, 15m, 10m |
| 40m | ~66 ft | ~20.1 m | 20m, 15m, 10m |
| 20m | ~33 ft | ~10.0 m | 10m |
These lengths are starting points. Cut your wire a foot or two longer than the table above, then trim for minimum SWR on your fundamental band using an antenna analyzer. The 40m EFHW at 66 feet is the most popular all-around choice for fixed home stations and portable use.
What You Need
Shopping List
- Wire — 18–16 AWG stranded copper wire. Antenna Warehouse sells it by the foot. DX Engineering's DX-Wire is excellent for portable use (light and strong).
- 49:1 UNUN matching transformer — Buy a commercial unit (Chameleon, Balun Designs, or MyAntennas EFHW kits) or wind your own on a FT-240-43 toroid. Commercial units rated for 100W+ are around $40–$80.
- Coax feedline — RG-8X or LMR-400 from the transformer to your radio. Length doesn't matter for an EFHW — the coax is not part of the radiating system.
- A counterpoise wire — 16–18 feet of wire connected to the ground terminal of the UNUN. Critical — skip it and you'll have RF on your coax braid and potentially in your shack.
- Rope and an end insulator — To support the far end of the wire. Dacron rope holds up well outdoors.
- Antenna analyzer (recommended) — MFJ-259C or a NanoVNA (~$50) to trim the wire to resonance.
Step-by-Step Installation
Step 1 — Identify Your Installation Path
The wire needs to run as high and as straight as possible — not because it won't work bent, but because more height and less bending means better radiation at lower takeoff angles for DX. Ideal: one end supported at 30–40 feet, the far end in a tree or on a mast. Common real-world configurations: sloped from a 2nd-story window to a fence post, inverted-V from a single central mast, or an L-shape around the back corner of a house. All of these work.
Step 2 — Mount the UNUN at the Low End
The matching transformer mounts at the feedpoint — wherever the coax meets the wire. For a sloped configuration, this is typically at the lowest point (near the house). Mount it on a non-conductive bracket if possible. Keep the box away from metal surfaces, which can detune it. Run coax from the UNUN to your radio; run the counterpoise wire from the ground terminal away from the antenna and house at ground level or along the ground.
Step 3 — Run the Wire
Connect the wire to the terminal on the UNUN. Run it as high and as straight as you can manage, supporting the far end with rope and an insulator. Keep the wire away from metal gutters, downspouts, and utility lines.
Step 4 — Trim to Resonance
Connect your antenna analyzer to the coax at the shack end. Check SWR on your fundamental band. If it's high (above 2:1), trim the wire in 2-inch increments from the far end and recheck. Most properly-wound 49:1 UNUNs will produce SWR under 1.5:1 with a well-cut wire. On harmonic bands, check SWR there too — usually fine without additional trimming.
Step 5 — Install a Ferrite Choke (Optional but Recommended)
Even with a counterpoise, some common-mode current can ride back down the coax. Adding a simple ferrite choke (6–8 turns of coax through a FT-240-31 toroid) right at the UNUN output port eliminates this. Signs you need one: RF in the shack, audio feedback, or your computer USB ports misbehaving on transmit.
EFHW for Portable / POTA Use
The EFHW is the dominant antenna at POTA and SOTA activations for good reason. A 40m EFHW weighs practically nothing — 65 feet of light wire, a small UNUN box, 20 feet of coax, and you're operational in under 10 minutes. Throw the far end over a tree branch with a fishing weight, prop the feed end on a telescoping mast or trekking pole, connect the counterpoise along the ground, and you're making contacts.
Commercial options worth looking at: the Chameleon EMCOMM III Portable and the MyAntennas EFHW-8010-1K are popular ready-to-go kits that include the transformer and pre-cut wire.
Common Problems
SWR is flat but I'm getting RF in the shack
Counterpoise is missing or too short. Add a 17-foot radial from the ground terminal of the UNUN and run it away from the antenna. This is the number-one setup error with end-fed antennas.
SWR is all over the place — won't go below 3:1
Check your UNUN — poorly wound transformers are the most common cause of an EFHW that won't tune. A quality commercial UNUN (Balun Designs, Chameleon) eliminates this variable. If you wound your own, verify turns count and core material (FT-240-43, not -61 or -77).
Wire keeps blowing around
That's normal. A slight sag or sway doesn't affect performance meaningfully. If the wire is touching a tree branch repeatedly, you'll see SWR variation — just adjust the support point.
Use our free Antenna Length Calculator to compute the exact wire length for any band. Enter your target frequency and it returns the half-wave length, accounting for velocity factor.