ABSTRACT
In accordance with the equivalence theorem, when considering electromagnetic fields in a free space surrounding a radiator, an antenna should be replaced by a field at the boundaries. The experimental method for determining the radiation resistance is based on measuring the signals received by investigated and reference antenna from the same source. The generalization of the expressions for the current and the input impedance of a metal antenna to the case of an antenna with a constant surface impedance allows application of the induced emf method to calculate an input impedance of an impedance antenna. An antenna with constant surface impedance is a particular case of a radiator with impedance changing along the antenna. After switching on the first load, the directional pattern changed significantly; after switching on the second load it changed slightly and after switching on the third load, the change became invisible.
