By Danny Horvat, E73M / N4EXA — antenna design engineer and founder of MyAntennas.com.
Overview
The EFLW and the EFHW are both fed at one end, but they are two different antennas built on opposite design principles. The EFHW is a resonant half-wave wire matched by a high-ratio transformer; the EFLW is a deliberately non-resonant wire matched by a 9:1 UNUN and an antenna tuner.
EFLW (End-Fed Long Wire) and EFRW (End-Fed Random Wire) are two names for the same antenna. “Random” is a misnomer: the wire lengths are chosen carefully so they are not resonant on the amateur bands. Our EFLW-3K covers 1.8–54 MHz at 3 kW ICAS and always requires a tuner.
The practical takeaway: an EFHW gives you low SWR on its design bands with no tuner, while an EFLW gives you every band from 160 to 6 m, including WARC and 60 m, as long as you bring a wide-range tuner.
How the EFLW works
The EFLW relies on a conjugate match by the tuner, not on resonance. The 9:1 UNUN does not “match” the antenna; it moves the feedpoint impedance into a range your tuner can handle.
- Feedpoint impedance varies by band. On a non-resonant wire it is complex (resistive plus reactive) and changes from band to band. A 9:1 UNUN is a 450:50-ohm transformer, so it centers the transformed impedance in the tuner’s comfort zone rather than at 50 ohms.
- SWR at the radio is not low, and it is not supposed to be. Expect anywhere from about 1.5:1 to 10:1 depending on band, wire length, coax length, and wire geometry. This is normal EFLW behavior, not a defect.
- The transformer itself is low loss. Our 9:1 UNUN is wound with PTFE wire on two 2.9-inch ferrite toroids. Terminated into 450 ohms, its SWR is nearly flat from 1–30 MHz, with insertion loss under 0.1 dB at 1.8 MHz and about 0.2 dB at 28 MHz.
- System loss lives elsewhere. Additional loss comes from mismatch on the coax and from the tuner. Keep the coax run reasonable and use low-loss cable on the higher bands.
Because the wire is not resonant, it has no “design bands.” Every band is a tuner band — which is exactly what gives the EFLW its 160–6 m coverage from a single wire.nds”. Every band is a tuner band, which is exactly what gives the EFLW its 160–6 m coverage from a single wire.
How the EFHW works, for contrast
The EFHW is resonant by design: the wire is a half wavelength on its lowest band, and therefore a multiple of a half wave on its harmonically related bands. The end of a resonant half-wave is a high-impedance, low-current point — typically a few thousand ohms.
- High-ratio transformer. That high impedance calls for a high-ratio transformer (49:1 class), not a 9:1. The transformer’s job is a true impedance match, so SWR is low on the design bands without a tuner.
- Multiband by harmonics. A 130 ft EFHW such as the EFHW-7510-2K-Plus is resonant on 75/40/30/20/17/15/12/10 m from one wire, with no tuner needed.
- No counterpoise required. Current is at a minimum at both ends of a half-wave, so the current at the feedpoint is small. The antenna does not need a ground plane to work against — see About Counterpoise.
For the full story on EFHW theory, installation, and trimming, see All About EFHW Antennas.EFHW Antennas.
Counterpoise and common-mode current
This is the most important operational difference. An EFHW needs no counterpoise; an EFLW needs a return path. On a non-resonant wire the feedpoint current is substantial, and that current has to flow against something. This is the one case in our lineup where a real counterpoise does real work.
- The coax shield is usually the return path. The EFLW works without radials as long as the coax is at least 25 ft long — the outside of the shield becomes the other half of the antenna. Even so, short radials (10–30 ft long) around a ground rod at the UNUN are highly recommended; anywhere from 2 to 16 radials will help, and more is better.
- Inverted-L close to the ground. Here a ground connection (radials) at the wing nut next to the SO-239 is recommended.
- A CMC choke is strongly recommended. Because the shield carries antenna current by design, it will bring RF into the shack unless it is stopped. Place a choke such as the CMC-154-3K at the cable entry point, not at the radio. The section of shield between the UNUN and the choke is part of the counterpoise, together with the ground rod and radials. Everything after the choke stays quiet. (Placement details: About CMC.)
- Expect more RF management than with an EFHW. RF on USB/CAT cables, SWR that changes when you touch the radio, and higher receive noise are classic symptoms of an unchoked EFLW feedline — not of a bad UNUN.
On an EFHW, a CMC is about keeping residual common-mode current off the feedline. On an EFLW, it defines where the antenna ends.
Note on grounding: the radials and rod described here are part of the EFLW antenna system. They are separate from safety grounding, which is still done by bonding the coax shield at the house entrance per NEC-810 — see About Grounding.C is about keeping residual common-mode current off the feedline. On an EFLW, it defines where the antenna ends.
Choosing an EFLW wire length
Pick the longest wire your site allows from the lengths we offer. Two rules drive the choice:
- Avoid half-wave multiples on the HF bands. At those lengths the feedpoint impedance climbs to several thousand ohms — beyond what a 9:1 UNUN can bring into tuner range. Our lengths are cut to stay clear of resonance on the HF bands, so do not trim them to “tune” the antenna. (On 6 m the half-wave spacing is only about 9 ft, so no practical length avoids it entirely; a wide-range tuner handles it.)
- Aim for at least a quarter wave on your lowest band. Shorter wires will often still load with a good tuner, but efficiency and bandwidth drop quickly below about ¼ wavelength.
| Wire length (ft) | Lowest band at > ¼ wl | Typical use |
|---|---|---|
| 44 | 40 m | Portable, RV, attic, 40–6 m focus |
| 60 | 60 m | Small lots, 60–6 m |
| 73 | 80 m | Most popular backyard size |
| 88 | 80 m | Better 80 m efficiency |
| 107 | 80 m | Strong 80 m, usable 160 m with tuner |
| 140 | 160 m | Entry point for full 160 m use |
| 173 | 160 m | Low-band DX, inverted-L |
| 202 | 160 m | Best 160 m performance |
“Lowest band” is a rule-of-thumb guide based on ¼ wavelength = 246 ÷ f (MHz) feet. Height, geometry, and nearby objects all shift real results.
Side-by-side comparison
| EFLW / EFRW | EFHW | |
|---|---|---|
| Design principle | Non-resonant on every band | Resonant half-wave + harmonics |
| Transformer | 9:1 UNUN (450:50 Ohms) | High-ratio (49:1-81:1 class) |
| Feedpoint impedance | Varies widely, reactive | High and fairly predictable |
| Tuner | Always required, wide-range | Not needed on design bands |
| Band coverage | 160–6 m incl. WARC and 60 m | Design bands only (e.g. 75/40/30/20/17/15/12/10 m on 130 ft) |
| Typical SWR at radio | 1.5:1 to 10:1 | Low on design bands |
| Counterpoise | Needed: coax shield (> 25 ft) or wire radials | Not needed |
| CMC choke | Strongly recommended | Optional; recommended for RFI or noise |
| Wire length | Fixed, chosen to avoid resonance; do not trim | Cut for resonance; trim by cutting |
| Feedline loss | Higher, due to mismatch on coax | Low |
| Best suited for | All-band coverage, odd lots, low bands, MARS | No-tuner operation, amplifiers, contesting |
Installing the EFLW
The EFLW is the most forgiving end-fed to install, but the feedline is part of the antenna, so treat it that way.
- Mount the UNUN on a pole, fence, or building with the installation plate, clear of metal where practical.
- Run the wire in whatever geometry the site allows: sloper, inverted-L, straight, zigzag, vertical, or horizontal. Polarization follows the installation. Let it hang with natural sag; it does not need to be pulled taut.
- Use at least 25 ft of coax from the UNUN. For inverted-L installs close to the ground, add a ground or short counterpoise wire at the wing nut.
- Install a CMC choke at the cable entry point to the shack.
- Tune with a wide-range tuner. A radio’s internal tuner will handle many bands; 160 m and some higher bands will usually need an external tuner. A remote tuner at the feedpoint reduces coax mismatch loss.
Common support question: “It has high SWR on every band.” That is the expected behavior of a non-resonant antenna. The test is whether the tuner can match it, not what the SWR meter reads without one. (More on reading SWR: About SWR.)uestion: “It has high SWR on every band.” That is the expected behavior of a non-resonant antenna. The test is whether the tuner can match it, not what the SWR meter reads without one.
Which one to choose
Choose by whether you want to run a tuner, not by which antenna is “better.” Both radiate well when installed correctly.
- Choose the EFHW if you want low SWR with no tuner, run an amplifier, operate mostly on the main HF bands, or want the simplest RF environment in the shack. Shop EFHW antennas.
- Choose the EFLW if you want every band from 160 to 6 m, including 60 m and WARC, need MARS frequencies, have an awkward lot that doesn’t fit a resonant length, or already own a capable wide-range tuner. Shop EFLW antennas.
- Portable and stealth (HOA, RV, Field Day, sailboats, attics) suit both. The EFLW is more tolerant of whatever length and shape the site forces on you; the EFHW gets you on the air without a tuner.
Frequently Asked Questions
What is the difference between a 9:1 UNUN and a 49:1 transformer?
A 49:1 transformer matches the high impedance at the end of a resonant half-wave wire down to 50 ohms, so no tuner is needed on the design bands. A 9:1 UNUN only brings a non-resonant wire’s impedance into a range a tuner can match; it always needs a tuner.
Can I use a 9:1 UNUN with a half-wave wire?
No. A half-wave wire presents a few thousand ohms at its end — far beyond what a 9:1 can bring into tuner range. That is exactly why EFLW wire lengths are chosen to avoid half-wave multiples.
Does an EFLW need a counterpoise?
Yes, it needs a return path. At least 25 ft of coax usually provides it via the shield, and short radials at a ground rod at the UNUN improve it. A choke at the cable entry point marks where the antenna system ends.
Should I trim my EFLW wire to lower the SWR?
No. The lengths are chosen to stay non-resonant. Trimming can move a harmonic into a band and push the impedance out of the tuner’s range. Let the tuner do the matching.
Which is better for DX?
Neither is inherently better — radiation depends on height and geometry, not on the transformer ratio. The EFHW is simpler and lower-loss on its design bands; the EFLW wins on band coverage.
Related products: EFLW-3K · 9:1 UNUN · EFHW-7510-2K-Plus · CMC-154-3K
Related reading: All About EFHW Antennas · About Counterpoise · About CMC · About Grounding · About SWR
