Abstract: A shell structure for a collinear coaxial element array antenna is made of electrical conducting material and includes first and second circular sections separated by a web. The first circular section has an inner diameter that is slightly larger than the diameter of an inner conductor in a coaxial line element of the array antenna, while the second circular section has an inner diameter that is equal to that of an outer conductor of a coaxial transmission line element. The separations of the centers of the first and second circular sections are established by the wed to be equal to the distance between the centers of two adjacent coaxial transmission line elements in the array antenna. The inner conductor of a coaxial transmission line element is inserted in the first circular section and is electrically connected thereto.

Abstract: An array of collinear coaxial lines utilizes standard size brass tubing with brass rods inserted therein to establish each half-wavelength coaxial section. A coupler positioned between each half-wavelength section has an outer conductor supports and through passages for the inner conductor. Inner conductors of the transmission line elements are soldered to the outer conductors of the respective adjacent transmission line elements so that all elements are excited with the same phase and polarity. Air dielectric between the inner and outer conductors provides a transmission line wavelength equal to that of free space so that the length of each element in the array is a free space half-wavelength long, thereby providing an antenna gain greater than that achievable with transmission lines having solid dielectric supporting the inner conductor.