Use this electronics calculation for a first-pass component, converter, signal, motor, or sensor estimate when the stated operating conditions and units match the device data.

Gain (dBi)

Measured antenna gain.

Efficiency Fraction

Radiation efficiency as a fraction strictly between zero and one.

Recover antenna directivity as directivityDbi = gainDbi - 10 * log10(efficiencyFraction), with efficiency defaulting to 0.6. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Directivity (dBi)

Antenna directivity.

• Antenna formulas assume stated frequency, impedance match, polarization, efficiency, aperture, and propagation geometry. Nearby objects, ground, feed loss, multipath, regulatory averaging, near-field conditions, and pattern variation can make free-space or ideal-aperture results inaccurate.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check the result against the current datasheet and worst-case operating corners, then verify the circuit or measurement with simulation and bench testing where failure matters.

• Antenna Rad Efficiency 2

  Infer antenna radiation efficiency in percent from measured gain and directivity via efficiencyPercent = 10^((gainDbi - directivityDbi) / 10) * 100.

• Gain From Aperture

  Compute the linear antenna gain as G = 4 x pi x A x eta / lambda^2 with aperture efficiency eta between zero and one, defaulting to 0.55.

• Parabolic Dish Gain dBi

  Compute parabolic dish gain in dBi as 10 x log10(eta x (pi x D / lambda)^2); eta defaults to 0.55.