CB Antenna Length Calculator
Quarter-wave and dipole lengths for the 27 MHz CB band — why the classic whip is 102 inches, which channel to tune for, and how to read SWR like a tech.
Preset: quarter-wave whip at channel 19 (27.185 MHz) → ~2.62 m / 103 in. Switch to half-wave dipole for a base-station wire antenna — each leg ~2.6 m, fed with 50–75 Ω coax.
CB Antenna Length Calculator computes quarter-wave whip and dipole lengths for the 27 MHz Citizens Band — free, instant and private in your browser. CB operators, truckers and overlanders tuning whips and base antennas use it to skip the datasheet algebra: type your numbers, read the answer with the substituted formula shown step by step, and share an exact permalink of the calculation.
About CB Antenna Length Calculator
CB Antenna Length Calculator computes quarter-wave whip and dipole lengths for the 27 MHz Citizens Band using the standard engineering relation: λ = c/f, L = 0.25·λ·k with k ≈ 0.95 thin-wire end effect. Worked live: at channel 19 (27.185 MHz) the quarter wave is 2.62 m — the classic 102-inch steel whip plus its spring base. The result recalculates on every keystroke, the worked-example panel shows your numbers substituted into the formula, and the Copy permalink button encodes the inputs in the URL so a colleague opens exactly your calculation. Everything runs client-side — nothing you type leaves your device.
How to use CB Antenna Length Calculator
- 1Enter your values — the tool starts with realistic defaults for this exact use case, so the worked example is meaningful immediately.
- 2Read the live result and the worked-example panel, which substitutes your numbers into the formula step by step.
- 3Adjust any input to compare scenarios, then use Copy result or Copy permalink to share the calculation.
Why use CB Antenna Length Calculator?
- ✓Implements the real formula — λ = c/f, L = 0.25·λ·k with k ≈ 0.95 thin-wire end effect — with the substitution shown, not a black box
- ✓Built for CB operators, truckers and overlanders tuning whips and base antennas
- ✓Copy result and permalink buttons — share the exact calculation in a README, forum answer or design review
- ✓100% free, no sign-up, runs entirely in your browser (works offline once loaded)
Frequently asked questions
How do you calculate cb antenna length?+
Quarter-wave whip and dipole lengths for the 27 MHz Citizens Band follows λ = c/f, L = 0.25·λ·k with k ≈ 0.95 thin-wire end effect. For example, at channel 19 (27.185 MHz) the quarter wave is 2.62 m — the classic 102-inch steel whip plus its spring base. The calculator applies the same relation and shows the substituted arithmetic so you can verify every step.
How do I tune a CB antenna with an SWR meter?+
Read SWR at channels 1 and 40. Higher at 40 means the antenna is too long — trim 6 mm at a time; higher at 1 means too short — add a spring or extend the tunable tip. Aim for under 1.5:1 at channel 19; under 2:1 across the band is a healthy install.
Why do loaded (short fiberglass) CB antennas perform worse?+
The loading coil replaces missing physical length electrically but can't radiate — its resistance converts transmit watts to heat, and the shorter radiator has narrower bandwidth. A full 102-inch quarter wave on a good ground plane outperforms any 3–4 ft loaded whip; the loaded antenna trades dB for garage clearance.
Is the CB Antenna Length Calculator free and private?+
Yes — completely free with no sign-up or usage limits, and it runs entirely in your browser: the values you enter are never uploaded or stored on a server.
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