`dB_"from peak main beam" = 10*log_"10"(|2* (J_1( "X" ))/ "X" |^2)`

Enter a value for all fields

This vCalc antenna equation computes the radiation directivity of a circular antenna at various angles from the peak of the main beam.  This equation assumes the antenna has a uniform amplitude distribution and is calculated from the zero-order Bessel Function of the first kind (`J_1(X)`).

The units dBi is the decibels relative to an isotropic antenna.

Examples

The peak of the first lobe of a circular antenna calculated here is at `X approx 5.14` and it's directed power is approximately -17.57 dB.

See also

Discussion of Beamwidths and Sidelobe Levels