Measurements of the impedance of a cylindrical antenna in an isotropic plasma and a comparison with theory have been made.The length of the antenna is comparable to the free space length.The EMF method was employed.Since sine and cosine integrals for complex arguments are not available,direct calculations have been made by substituting complex numbers into relevant expressions.The results showed an agreement between predicted and measured values,especially around plasma fre-quancies.This may be of some practical significance for the calculations and the measuring system described here in applications to certain spase plasma investigations.