Optimal NVIS Antenna Heights for Reliable HF Coverage
NVIS (Near Vertical Incidence Skywave) is what makes HF work reliably for regional coverage when hills, forests, and buildings block line-of-sight. The goal is simple: push most of your energy upward (high elevation angles), so it comes back down nearby instead of leaving as low-angle DX.
Why 0.18–0.22λ is the “safe bet” height
For classic NVIS antennas (horizontal dipoles and inverted-Vs), the most repeatable NVIS transmit geometry is a low installation height around 0.18–0.22 wavelengths (λ) at the feedpoint.
Rule of thumb: NVIS is mostly about elevation angle control. Height sets the lobe. Feedline control (a good 1:1 choke) keeps that lobe from being “dragged around” by coax radiation.
- Too low (≈0.15λ and below): ground loss rises and efficiency drops.
- Too high (≈0.25λ and above): the pattern flattens, and more energy leaks into lower angles (less useful for regional fill-in).
- In the middle (0.18–0.22λ): strong high-angle energy, predictable footprint, and a forgiving setup window.
Recommended NVIS feedpoint heights by band
The table below shows practical feedpoint heights that land in the 0.18–0.22λ window on typical NVIS bands. For an inverted-V, put the center here; the ends can slope down safely.
| Band | Frequency (MHz) | Wavelength (λ) | Target feedpoint height (m) |
|---|---|---|---|
| 30 m | 10.1 | 29.7 m | 5.3 – 6.5 |
| 40 m | 7.1 | 42.3 m | 7.6 – 9.3 |
| 60 m | 5.3 | 56.6 m | 10.2 – 12.5 |
| 80 m | 3.6 | 83.3 m | 15.0 – 18.3 |
| 160 m | 1.9 | 157.9 m | 28.4 – 34.7 |
Receive vs. transmit optimization: many operators observe that the “best” height on receive can be a bit lower than the best transmit footprint on the same band. That doesn’t break reciprocity; it’s usually local noise pickup, ground loss, and day-to-day ionospheric absorption shaping what sounds best. If you want to tune for receive SNR first, start here: Understanding Optimal NVIS Receive Angles.
Practical install tips
- Supports: trees or lightweight masts make NVIS heights easy on 40/30 m; 80 m needs more structure.
- Soil and loss: poor soil often benefits from aiming toward the top of the range (closer to 0.22λ).
- Multi-band compromise: setting the feedpoint around the 60 m target (≈11 m) is often a strong compromise for 80/60/40 m.
- Polarization: NVIS likes horizontal fields. Keep vertical drops short and keep the feedline under control.
- Choke at the feedpoint: add a 1:1 current choke at the feedpoint to reduce feedline radiation and stabilize your pattern.
- Avoid “too high” installs: if you want regional coverage, avoid heights above ≈0.3λ that push energy into shallower angles.
Done right, a simple wire NVIS antenna delivers dependable “fill-in” coverage for local nets, emergency comms, and day-to-day regional QSOs — even when terrain blocks VHF/UHF.
Mini FAQ – NVIS Antenna Height & Setup
- What height should I use? Aim for ~0.18–0.22λ at the feedpoint. For 80 m that’s ~15–18 m; for 40 m ~7.6–9.3 m.
- Does polarization matter? Yes — NVIS favors horizontal antennas (dipole/inverted-V). Verticals favor lower angles.
- Can I do NVIS on 20 m? Usually not. True NVIS at 14 MHz is uncommon; 80/60/40 m are the staples.
- Should I add a choke? Yes. A 1:1 current choke at the feedpoint lowers noise pickup and improves pattern consistency.
- Is an inverted-V OK? Yes — set the feedpoint at the target height; legs can slope down safely.
Interested in more technical content? Subscribe to our updates for deep-dive RF articles and lab notes: RF.Guru technical mailing list
Questions or experiences to share? Feel free to contact RF.Guru: contact RF.Guru.