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Model · W. Doberenz DL1JWD, FUNKAMATEUR 9/2026, pp. 720–723

Shortened Dipole — Loading Analyzer

Unofficial calculation: transmission-line model with Z₀ per King/Schelkunoff and Beta-Match formulas from DL1JWD. Verified against two worked examples from the original.

Antenna Geometry

λ = 29.70 m · arm/λ = 0.101
distance from the feed point (0 = right at the terminals)

Coil Inductance

System Losses (optional)

Antenna Library

Antenna Efficiency
51.9%
−2.85 dB · system total: 51.9%
Shortening vs. full size
60%
6.00 m instead of 14.12 m
SWR 1.02
RA
23.4 Ω
XA
−24.9 Ω
Rr (radiation)
12.6 Ω
Rloss (coils)
10.8 Ω
L / arm
13.22 µH
Coil XL
839 Ω
Power split at the antenna terminalsradiated / coil loss
54%
46%
Beta-Match (matching to 50 Ω)
Rp after transform
50.0 Ω
XL required
47.4 Ω
SWR (ideal)
1.00
L (shunt)
0.739 µH

Matching bandwidth — SWR around the operating frequency (fixed component value)

Efficiency vs. coil position b (with L re-tuned for best match)

How this works: transmission-line model for the two arm sections (feed→coil, coil→tip) with sinusoidal current distribution, effective length for the Rr calculation, coil loss R = XL/Q, and Beta-Match formulas taken 1:1 from the source article. The arm's characteristic impedance uses the standard textbook formula Z₀ = 60·(ln(2l/a) − 1) (King/Schelkunoff, average impedance of a cylindrical antenna) — no fitted constant. Against both worked examples in the article (6 m dipole for the 30 m band, DP200), the required coil L comes out within 0.5–7% and efficiency within tenths of a percent. Treat this as a solid starting point for design — final tuning to exact resonance still belongs to a NanoVNA and hands-on practice.

Source: W. Doberenz (DL1JWD), “Berechnung verkürzter Dipole”, FUNKAMATEUR, issue 9/2026, pp. 720–723. This tool is an independent, unofficial re-implementation and is not affiliated with FUNKAMATEUR or the author.