INTERACTIVE TOOLS
Quick radio calculators
Useful starting estimates for learning and planning. Confirm calculations against your equipment and conditions.
Wavelength
Free-space estimate from frequency in MHz.
Antenna starting length
Quarter-wave estimate in metres using a velocity factor.
Radio horizon
Approximate line-of-sight horizon for two antenna heights.
SWR reflection
Estimate reflected power fraction and return loss.
Ohm’s law
Current and power from voltage and resistance.
Battery runtime
Simple estimate using usable capacity and average current.
Maidenhead locator
Convert decimal latitude and longitude to an approximate 6-character locator.
Antenna lengths and radio horizon are approximations. SWR calculations do not determine whether a transmitter, antenna or operating condition is compliant or safe.