14 ham radio antenna and RF calculators.
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Half-wave dipole length (total and each leg) for any frequency.
Radiator and radial lengths for a quarter-wave ground-plane vertical.
Total and side length of a full-wave delta or quad loop.
Radiator and matching-stub lengths for a J-pole VHF/UHF antenna.
EFHW wire length plus the harmonic bands it also covers.
Starting-point reflector, driven and director lengths plus spacing for a Yagi.
SWR to reflection coefficient, return loss, mismatch loss and reflected power.
dBi to dBd, and ERP / EIRP from power, feedline loss and gain.
Convert RF power between dBm, watts, milliwatts and dBW.
Physical length of a quarter or half-wave coax stub, by velocity factor.
Frequency to wavelength in metres, feet and inches, plus the ham band.
Lowest-lobe elevation angle of a horizontal antenna from its height over ground.
Loaded Q and fractional bandwidth from centre frequency and bandwidth.
Grid locator to lat/long, plus distance and beam heading to another grid.
A set of ham radio calculators for antennas and RF: cut a half-wave dipole, quarter-wave vertical, full-wave loop, J-pole or end-fed half-wave, lay out a Yagi, work out SWR and return loss, antenna gain with ERP and EIRP, dBm to watts, coax stub lengths, wavelength, takeoff angle, antenna Q, and Maidenhead grid distance and beam heading. Standard formulas, all in your browser.
Antenna lengths use the standard ham formulas (468 / MHz for a half-wave dipole, 234 for a quarter wave, 1005 for a full-wave loop), and the RF tools use the exact SWR, decibel and great-circle formulas. Real antennas vary a few percent with wire diameter, height and surroundings, so cut a little long and trim for lowest SWR.
The Yagi tool gives a proven starting point, not a finished design; optimise element lengths and spacing with modelling software such as EZNEC or 4nec2. The wire-antenna and RF calculators are exact for their formulas.
No. Every calculator runs entirely in your browser with no download, sign-up, or data leaving your device.
Dipole, quarter-wave vertical, full-wave loop, J-pole, end-fed half-wave, Yagi, SWR, antenna gain (ERP / EIRP), dBm to watts, coax stub, wavelength, takeoff angle, antenna Q and the Maidenhead grid locator.