A note on the criteria for the far zone in the time-domain analysis of antennas

The basic traveling-wave element is considered as a model for an antenna radiating a pulse. The exact expressions for the electromagnetic field of the element throughout all space are used to obtain power series for the field in the variable h/r<1, where h is the length of the element and r is the distance from the element. These series are then used to develop criteria for estimating when the distance from the element is sufficient for the field to be a good approximation to the far-zone field.