Why a 9:1 Long-Wire Works… Why It’s Less Efficient than the EFHW/OCF

Short version: A 9:1 long-wire “random” antenna absolutely works and can cover many HF bands with one wire. But for the same physical space, it is typically a few to many dB less efficient than resonant systems like EFHWs or near resonant ones like the OCF dipoles and the End Fed Off Center (Fed) EFOC. That’s why many operators treat it as an emergency or universal fallback antenna, not their primary station antenna.

This article explains where the losses come from, how large they typically are, and why the lengths 51 m, 37 m, and 22 m are smart choices when using a 9:1.

Why a 9:1 Long-Wire Loses Efficiency

The wire itself is not the problem. Once a conductor is about 0.25 λ long on a band, it radiates very well. The real inefficiency comes from everything around the wire:

• the 9:1 UNUN
• the tuner working outside resonant ranges
• the ground or counterpoise path
• the coax operating at high SWR

Loss inside the 9:1 UNUN

Measured values of a typical T-200-2 9:1 voltage UNUN:

• 160 m: ~5.2 dB loss (only ~30% of RF reaches the radiator)
• 80 m: ~3.1 dB loss (~50% lost in the core)
• 40–12 m: under 1 dB loss → almost negligible
• Above 25–30 MHz: slight increase again

This means on the low bands, the transformer alone can cost one to two S-units.

Additional tuner losses

A random wire can present very high, very low, or highly reactive impedance. Tuners are least efficient here. Most operators see:

• 1–3 dB additional loss on the difficult bands
• especially when the tuner inductors run high circulating currents

Ground / counterpoise losses

A 9:1 long-wire always needs a return path:

• Ground rod only → lots of current into lossy soil
• Coax shield as counterpoise → feedline radiation + loss + RF in the shack
• Radials or a proper counterpoise → much cleaner and more efficient

Coax losses at high SWR

If the tuner sits in the shack, the coax runs at very high SWR on most bands. Even good coax can lose:

• 1–3 dB extra depending on frequency and length

This is why many operators say a 9:1 wire is “several dB down” from an EFOC in the same location.

Real-World Efficiency on Each Band

Assuming a decent installation with a short coax run and a reasonable counterpoise:

• 40–12 m: 2–4 dB down from a resonant antenna (roughly 40–65% efficiency)
• 80 m: 5–7 dB down typical (one S-unit or more)
• 160 m: 8–13 dB down common (1.5–2+ S-units)

These numbers line up very closely with field reports: A 9:1 wire is usable and often excellent on mid-HF, but clearly disadvantaged on 80 m and 160 m.

Why 51 m, 37 m, and 22 m Are Smart Choices

These lengths avoid the worst feed-point impedance peaks and align with values published by several well-known 9:1 UNUN manufacturers.

• 51 m: workable on 160 m, strong on 80–10 m
• 37 m: classic 80–10 m random-wire length
• 22 m: short 80–10 m length, slightly weaker on 80 m but good above

Why EFHW and OCF Designs Outperform 9:1 Long-Wires

For the same span of wire and the same supports, a resonant system (EFHW, OCF, or simple dipole):

• has far lower matching losses
• requires little or no tuner work
• has predictable patterns on each band
• is often 3–6 dB stronger than a 9:1 system in real tests

This is why resonant antennas remain the better everyday choice, while 9:1 wires shine as universal, flexible emergency antennas.

Getting the Most Out of a 9:1 Long-Wire

• Use real radials or a counterpoise (multiple short radials work well)
• Place the tuner near the feedpoint to avoid SWR on coax
• Choose a well-designed transformer (especially for 80/160 m)
• Stick to sensible lengths like 51 m, 37 m, 22 m

With these measures, a 9:1 long-wire can perform far better than many expect.

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