λ/4

Ground-Mount 1/4-Wave Vertical Calculator

Radial systems from 4 to 32 · live length solver

Methodology & Design Notes

The engineering behind radial length/impedance/efficiency: this is genuinely not a fixed physics constant — it's well-documented (particularly from Rudy Severns/N6LF's published ground-radial studies) that fewer, shorter radials mean more ground loss resistance, which raises the measured feedpoint impedance above the textbook 36Ω (which is why a lot of "just 4 radials" installations accidentally land near 50Ω) — while more/longer radials lower that loss resistance, improving efficiency but dropping impedance further from 50Ω, often needing a matching network. This calculator builds in a length/impedance/efficiency table across all six radial counts reflecting that tradeoff, clearly labeled as rule-of-thumb guidance rather than a precise NEC model, since real performance is soil-dependent.

Diagrams:

  • An elevation view showing the vertical element height and ground-level feed
  • A dynamically generated plan view — since "4 radials" and "32 radials" are fundamentally a top-down layout question, this draws N evenly-spaced spokes in real time based on your selection (verified: exactly 4 lines for N=4, exactly 32 for N=32)

⚡ Operating Frequency

Frequency (MHz) 7.150 MHz

Radial System

Vertical End-Effect Factor (K) 0.95
0.95 is the standard rule-of-thumb for AWG 12–14 wire or aluminum tubing. Radial length below is calculated separately, since a wire lying on/in the ground doesn't see the same end effect as the vertical element.

Calculated Results

Vertical Element Height: — ft / — m
Each Radial Length: — ft / — m
Total Radial Wire Needed: — ft / — m
Free-Space Wavelength (λ): — ft / — m
Approx. Feedpoint Z: — Ω
Approx. Ground-System Efficiency: —
Radial length and impedance/efficiency ranges are practical rules of thumb from published ground-radial studies, not a precise NEC model — real performance depends heavily on soil conductivity. More/longer radials lower ground loss and raise efficiency, at the cost of a lower (further from 50 Ω) feedpoint impedance.

Ground-Mount Vertical — Geometry

Not to scale · verify local clearance, safety, and code requirements before installation

Elevation View
ground radials (N shown in plan view) feed / coax shield Height: — ft
Plan View — Radial Layout
4 radials
Quick Reference — Common Amateur Bands
Uses current radial count & K-factor
Band Frequency Vertical Height (ft) Vertical Height (m) Radial Length (ft) Total Wire (ft)