Half-wave cylindrical antenna in a dissipative medium: current and impedance

An integral equat ion for t he distribution of curren t along a cylindri cal a ntenn a in a conducting dielectric is derived . It is shown t hat the boundary condi tions for a n antenn a in such a medium are formally t he same as for an a ntenn a in free space. The equation is solved for t he current I and t he driving-poin t impedan ce Z by means of a technique t hat achieves suffi ciently high accuracy in t he leading terms of an iteration procedu re so t hat t he higher-order terms do not need to be evaluated. Moreover, t hese leading te rms consist only of t rigonometric fun ctions wit h complex coeffi cients. The electromagnetic fi eld in t he infinite dissipat ive medium may be computed relatively eas ily s in ce t he current in th e ante nna is expressed in such sim pie terms. A llumerical a nalys is is made to determine t he propert ies of an antenn a with an electrical length of one-half wavelength in the medium with co nductiv ity q a nd relalive dielectric constant f ,. Universal curves a re given of I/";~--' with q / WfOf T as the parameter and of Z";;; wit h U / WfOf T as t he variable in t he range 0 S U / WfOf T S 0.4. A table of numeri cal values of t he impedance is g iven for media such as a n isotropic ionosphere, dry salt, dry earth, wet earth, a nd la ke water.