Comparing a 15m and 20m Mast for a Dual-Band 160/80m EFHW Inverted-L
Comparing a 15 m and 20 m Mast for a Dual‑Band 160/80 m EFHW Inverted‑L
The EFHW16080 in an Inverted‑L layout is a strong performer on the low bands. The length/height split between its vertical and horizontal sections sets takeoff angle, ground loss and how much energy goes into NVIS vs DX. Here we compare a 15 m mast against a 20 m mast.
EFHW 160/80 m Inverted‑L Setup
The EFHW16080 is a full‑size dual‑band wire antenna. In an Inverted‑L, the first segment rises vertically then transitions to horizontal. The vertical height strongly influences low‑angle DX potential and ground losses.
15 m vs 20 m Mast — Summary
| Parameter | 15 m Mast | 20 m Mast |
|---|---|---|
| Vertical segment | ≈15 m vertical + horizontal | ≈20 m vertical + horizontal |
| Ground losses | Higher (shorter vertical) | Lower (more height) |
| NVIS on 80 m | Stronger NVIS (regional) | Slightly reduced NVIS |
| DX on 80 m | Good, but more high‑angle energy | Lower takeoff → better DX |
| DX on 160 m | Moderate | Improved (lower angle) |
| Overall efficiency | Slightly lower (near‑field loss) | Higher (elevation gain) |
| Mechanical load | Lower; easier install | Higher; stronger guying needed |
Radiation Pattern Considerations
80 m:
- 15 m mast: Strong NVIS for regional contacts (few 100 km).
- 20 m mast: Slightly lower takeoff angle → more DX reach, still usable for NVIS.
160 m:
- 20 m mast: Clear DX advantage from lower takeoff angles.
- 15 m mast: Higher angles dominate → long‑haul DX more challenging.
Efficiency and Losses
- Shorter verticals couple more to the near field → higher ground losses. The 20 m mast has a consistent advantage.
- Radials/grounding matter in both cases; the taller vertical is less dependent on extensive radials than the shorter one.
Practical Considerations
Installation & Structural
- 15 m mast: Easier deployment, lower wind load — good for tight sites or moderate winds.
- 20 m mast: Stronger guying/hardware required; delivers better long‑distance (160 m) performance.
Conclusion
Pick the mast height that aligns with your goals:
- 15 m mast: Practical, NVIS‑friendly on 80 m; adequate DX on 80/160 m with simpler mechanics.
- 20 m mast: Best choice for DX‑first operation — lower takeoff angles and higher efficiency, especially on 160 m.
Mini‑FAQ
- Will a 20 m mast always beat 15 m? — For DX (lower angles), yes. For local NVIS on 80 m, 15 m can be stronger.
- How many radials do I need? — More and longer helps both, but the taller vertical is less radial‑sensitive.
- Does soil type matter? — Yes. Better ground (moist clay/loam) reduces losses; poor ground makes height even more valuable.
- Horizontal length vs height? — Height chiefly sets angle/ground loss; horizontal length fine‑tunes tuning and pattern fill.
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