Antenna length and dipole
How long does the wire need to be? Enter frequency and velocity factor and you get wavelength, dipole, leg length, quarter wave and five-eighths.
Antenna length
Free-space wavelength times velocity factor. For bare wire the factor is usually about 0.95, a little less for insulated wire.
How the page calculates
- ฮป = 299.792458 / f (ฮป in m, f in MHz)
- Half-wave dipole = ฮป ยท k / 2, each leg ฮป ยท k / 4
- Quarter-wave radiator = ฮป ยท k / 4
- Five-eighths = ฮป ยท k ยท 0.625
The result is a starting point for cutting: leave it a bit long and trim to resonance. Where resonance actually is, a meter tells you, for example via Measure an antenna.
Related terms
- Velocity factor
- factor between free-space wavelength and physical length; RG58 has 0.66, one metre takes 5.05 ns in it, try it out under /leitung
- Ground plane
- vertical radiator with radials as counterpoise
- End-fed
- wire antenna fed at one end, usually with a transformer