Vertical Antennas: Horizontal Clearance and DX Success

Horizontal clearance and nearby structures strongly affect vertical antenna performance. Getting clearance right is critical to low-angle DX radiation. Here’s what spacing matters by wavelength — and how it applies to different vertical designs.

Clearance vs Wavelength (λ): General Rules

Obstacles (buildings, fences, trees) within 0.1λ reflect/absorb RF and distort patterns. Use this clearance table for guidance:

Values scale similarly for higher bands (6–30 m). The higher the band, the smaller the required clearances.

Monoband 1/4λ Verticals with Rigid Radials

• Models: VertiCore (15–20 m)
• Feedpoint height: 1.0–1.5 m AGL ideal for DX
• Efficiency: High, due to rigid radials and raised feed
• Clearance tip: Maintain ≥0.2–0.25λ from obstacles

Monoband 5/8λ Verticals with Rigid Radials

• Models: VertiCore (10–12 m)
• Feedpoint height: 1.5–2.5 m AGL
• Pattern: Lower takeoff than ¼λ, but needs proper clearance
• Clearance tip: Keep base ≥0.25λ from walls or metallic objects

Ground-Mounted 1/4λ Verticals

• Note: Not offered as monobands by RF.Guru due to poor efficiency without elevated radials.
• Exception: VertX multiband fan vertical uses elevated feedpoint with radial field to achieve DX-capable performance (6–20 m).

RF.Guru Verticals: Clearance in Meters

We list clearances in meters because these antennas are multiband and have known geometry. Raised feedpoints (~1.1–1.5 m AGL) reduce obstacle sensitivity. Example: In a 20 m band setup with 1.5 m feedpoint, maintaining 2–3 m horizontal spacing from fences/walls is usually sufficient, even in urban gardens.

Examples

Xcentric (6–20 m Off-Center Vertical)

• Feedpoint: 1.5 m AGL
• Clearance tip: ≥1.5 m from metallic objects

VertX (6–20 m Fan Vertical)

• Feedpoint: 1.1 m AGL
• Clearance tip: ≥2–3 m from nearby walls/fences

IronWave 6 & 9

• Length: 6 m or 9 m aluminum radiators
• Feedpoint: 1.1 m AGL
• Clearance tip: ≥0.2λ from buildings; ideally in open field

DeltaRex Multiband Delta Loop

• Mounting height: 0.5–5 m AGL
• Clearance tip: Needs open area; avoid metallic clutter under/around loop

Final Tips

• For DX: prioritise feedpoint height, clearance, and radial quality
• In urban QTHs: loops and off-center designs help mitigate obstacles
• Avoid siting within 0.1–0.2λ of large buildings or metal sheds

Horizontal clearance is as important as vertical height — respect spacing rules for real DX success.

Interested in more technical content? Subscribe to our updates for deep-dive RF articles and lab notes.

Questions or experiences to share? Feel free to contact RF.Guru.