| 摘要 |
An antenna for use at frequencies of 200 MHz and upwards has a cylindrical ceramic core with a relative dielectric constant of at least 5, and pairs of helical elements extending from a feed point at one end of the core to the rim of a conductive sleeve adjacent the other end of the core, the sleeve acting as a trap for isolating from ground currents circulating in the helical elements. To yield helical elements of different lengths, the sleeve rim follows a locus which deviates from a plane perpendicular to the core axis in that it describes a zig-zag path. The helical elements form simple helices with approximately balanced radiation resistances.
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