an improved antenna of a coaxial type utilizing z - shaped slots disposed in the outer conductor to provide an omnidirectional antenna pattern . current coupling to the slots is achieved by means of the transverse portion of the z slot . detuning effects due to the presence of a transmission line are compensated for by dielectrically loading the slots with a dielectric cover over the coaxial line and / or by lengthening the longitudinal arms of the z . the longitudinal spacing between each slot and the length of the transverse portion of each slot are chosen while considering all line effects to obtain the required phase and amplitude relationships . the antenna consequently requires no additional coupling , tuning or phasing devices mounted within or without the coaxial line .