Calculation and application for the phase velocity of shortwave fish-bone antenna

An accurate method was proposed for the phase velocity along the central feeder of the fishbone antenna in this paper. The phase velocity of the fishbone antenna along any path of the feeder line was accurately calculated. The phase velocity of the central feeder between arbitrary dipoles elements was obtained. The phase velocity characteristics of the central feeder were studied. When the phase velocity is less than the velocity of light and close to the velocity of light, the average phase difference fluctuation range of the central feeder corresponds to the peak of the relative direction coefficient. The method of phase velocity optimization was carried out, and the gradient dipoles elements arm length can make the phase velocity close to the best velocity. The results show that the method of phase velocity calculation proposed in this paper is accurate and consistent with the theory, which applies to fishbone antennas in the actual environment. The directivity of the optimized antenna has an overall enhanced in the range of 4MHz∼30MHz compared with the conventional antenna, and the bandwidth is widened.