Coax Cut Length / Velocity Factor Calculator
Electrical quarter-wave and half-wave coax lengths by frequency and velocity factor.
Electrical lengths — VF 0.66 at 14.15 MHz
Quarter-wave (λ/4) — choke stub, matching section
Feet
11.469 ft
Meters
3.496 m
Half-wave (λ/2) — repeating impedance, phasing line
Feet
22.938 ft
Meters
6.992 m
Free-space λ/4: 17.378 ft · Free-space λ/2: 34.755 ft
Why velocity factor matters
EM waves travel slower in coax than in free space. The velocity factor (VF) is the ratio of propagation speed in the cable to the speed of light. A λ/4 stub cut to the free-space length will be electrically longer than intended — always apply VF.