A theoretical model of an infinite cylindrical antenna, fed by a delta-function generator and immersed in a compressible, isotropic, lossless plasma, is considered in detail. A modal solution is found for the associated wave-guide problem inside the antenna; apart from the slow mode, the wave-guide modes are grouped into three sets: optical, acoustic, and hybrid modes. The current wave on the outside wall of the antenna is separated into its components: the familiar electromagnetic wave, the "transverse electro-acoustic" wave which is due to the axial oscillation of electrons near the gap, and the slow surface wave. These wave components have been calculated numerically using an IBM 1130 digital computer. It is found that the electromagnetic as well as the "transverse plasma" waves have a logarithmic singularity at the gap. It is also found that at a relatively large distance from this gap the first component decays as [Formula: see text], while the second component decays very rapidly to zero.