7-element log-periodic antenna. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / VHF antennas
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While in Genoa, I met Gianni (5N0EIB) who works in the Nigerian capital. In a private conversation, Gianni told me the following amusing story.
Working in one of the responsible positions in a well-known oil company, Gianni has always been interested in amateur radio. Like all beginners, he did not have equipment, but the desire to work on the air was irresistible. Compiling the next report for the company's management, Gianni saw a special item on the questionnaire, where he was asked to give his thoughts on improving the work of the company's branch in Nigeria. Here Gianni felt that the idea had matured. He indicated in the questionnaire that the weather forecasts required for holidays are not received regularly and that colleagues at work cannot receive reliable information on time. Remembering his dream, he attached a list of equipment required by his branch to organize an amateur radio network for receiving weather reports. It included: two IC-731 transceivers, a pair of TS-940s for backup, 6 army auto-negotiated 4 kW power amplifiers (2 kW output in AM!), 1000 meters of coaxial cable, a pair of telescopic masts and other little things. What was the surprise of employees and work colleagues when several large containers were delivered to the name of Gianni on the next flight across the Atlantic. Yes, in America the initiative was always welcomed, and the company took care of the well-being of its employees in hot Nigeria.
A few months later, 3 amateur call signs were already sounding in those parts. Gianni carried away the radio of one of the communications staff, as well as a helicopter pilot. Soon, Gianni decided to dare in the design of antennas. having many programs for IBM-PC for calculating antennas, he created an optimized version of a seven-element log-periodic active antenna for 28 MHi with a rhombic reflector and fishbone elements.
A drawing of the half of the antenna (it is symmetrical and the second half is conventionally not shown) is shown in fig. 1. The antenna consists of a cubic reflector, five active elements and a director. The design of a cubic reflector is shown in fig. 2. It has been experimentally verified that this antenna has a higher gain than an in-phase array of two five-element wave channels spaced vertically.
Fig. 1 (click to enlarge)
Fig. 2
Author: N. Zhukovsky (U5UA), Kiev; Publication: cxem.net
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