Whip Antenna Calculator

Precision tool for whip / monopole design. Convert frequency ↔ length, apply shortening factor, visualize response. Trusted by ham radio operators and RF engineers.

Calculation mode:
MHz
Amateur, marine, CB, broadcast bands.
Enter desired whip length (mode: Length→Freq).
%
0.95 = 5% shortening (typical).
Common bands:
3.6 MHz (80m) 7.1 MHz (40m) 14.2 MHz (20m) 21.2 MHz (15m) 28.5 MHz (10m) 50 MHz (6m) 146 MHz (2m) 446 MHz (70cm)

Understanding Whip Antennas

A whip antenna is a monopole antenna mounted vertically, typically λ/4 long. Its physical length is shorter than the electrical length due to end‑effect and capacitive loading — accounted by velocity factor (shortening factor).

? Core formula (metric)

Physical length (m) = (300 / f_MHz) × (wavelength fraction) × velocity factor

For 1/4 whip, fraction=0.25, typical VF=0.95-0.98. Reverse: f = (300 × fraction × VF) / length_m

✂️ Common whip types
  • 1/4 wave (λ/4): Standard monopole, requires ground plane. Good match 50Ω.
  • 5/8 wave: Higher gain, needs matching coil; popular for mobile VHF/UHF.
  • 1/2 wave: End‑fed, requires high impedance matching; less common as pure whip.
? Velocity factor / shortening

End‑effect and diameter/length ratio reduce the resonant length. For thin whips: 0.97–0.98; for thicker whips or with loading: 0.85–0.95. This calculator uses a user‑adjustable VF.

Pro tip: For mobile HF whips, start with VF=0.95 and trim for minimum SWR. Always add 5–10% extra length for tuning.

Frequently Asked Questions

Electrical length corresponds to wavelength in free space. Due to capacitive end‑effect, the physical antenna is shorter. The ratio is velocity factor (VF).

Electromagnetic waves travel slower in a conductor than in vacuum. Also, the antenna’s tip capacitance makes it appear electrically longer.

This tool calculates physical length for a given frequency based on distributed shortening. For coils (base/mid loading), effective VF can be much lower (0.4–0.7). Enter custom VF for approximation.

Meters are standard for RF calculations, but you can output in cm, feet, inches. The internal calculation always uses meters & MHz.