Abstract: A multiple omnidirectional antenna, utilizing individual antennae for different frequencies, and/or different polarizations, disposed along a common axis, and employing a multiple coaxial feed from one side only, in which the omnidirectional antenna which is remote from the feed side, is in the form of an axial wave-guide section, with the portion defining the walls thereof being connected to the outer conductor of the innermost coaxial feed line, and at least, in effect, defining at least one slot therein which runs transversely to the desired polarization direction of such antenna, with the inner conductor of the innermost coaxial feed line forming the exciting element therefor and projecting into the interior of said wave-guide, and/or at least one other omnidirectional antenna in the form of a coaxial line section, the walls of which are connected to the outer conductor of another coaxial feed line, and are provided with at least one slot therein which runs transversely to the desired polarization directi

Abstract: A double omni-directional antenna for use with a transponder is disclosed allowing simultaneous operation within two different frequency bands. A double coaxial line is provided having outer, central, and inner concentric conductors. The outer and central conductors form a coaxial feed for a lower frequency antenna and the central and inner connectors form a coaxial feed for a high frequency antenna. The higher frequency antenna is located directly above the lower frequency antenna and each is either a unipole for vertically polarized radiation or a slot radiator for horizontally polarized radiation.