Dielectrically loaded antennas meet growing interest in wireless and satellite communication due to small dimensions, controllable properties and perfect protection from damages even in the case of explosions. Real construction can be computed using time domain finite difference methods, but those methods meet big difficulties in dynamic problems. The generalized eigenfunction method applied earlier to diffraction problems and in laser theory can help to find within the reasonably limited amount of calculation not only static but dynamic characteristics of antennas. The importance of the dynamic analysis is easily seen from the presented figures, which show big changes in antenna parameters in the case of transmission (or reception) of short pulses. For high bit rate communication systems the detailed analysis of such changes is of vital importance.