Multi-arm cylindrical folded dipole antenna for collinear arrays

A radiating element suitable for electrically long VHF/UHF collinear arrays is presented. Collinear arrays with an isotropic radiation pattern in the horizontal plane and vertical polarisation are usually made of stacked cylindrical dipoles. The proposed array element consists of a slotted cylindrical dipole and belongs to the class of transmission-line folded antennas. The structure of the proposed array element allows an easy and firm mechanical attachment to the metallic antenna mast, and at the same time it ensures a satisfactory isolation performance. Two prototypes operating at 300 MHz have been manufactured and characterised. The design procedure is described and measurements of the reflection coefficient and the isolation between adjacent elements are shown.