The directional gain and efficiency of a travelling wave V-antenna in the UHF band

To obtain a high directional gain, it is necessary to design the antenna so that the far ends of the arms contribute significantly to the transmitted power. Measurements of attenuation due to radiation and ohmic losses are made on three antennas having arms of different cross-sectional area. The values obtained are used in theoretical calculation of the gain of V-antennas as a function of arm lengths for optimized apex angles. The results indicate that the gain reaches a maximum when the arm length is about 4 m and decreases for further increase in arm length. This anomaly is explained by the fact that in optimizing the apex angle, it was assumed that no attenuation occurred along the arms. In the case of UHF antennas having arms with relatively large cross-sectional area, the ends of the V-antennas do not radiate significantly and are, in fact, unnecessary. When the computer was instructed not to adjust the apex angle for lengths beyond 4 m, the calculated gain characteristics changed, and the maximum gain of the antenna was about 19 dB. This result was verified by measurement.<>