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A vertically polarized antenna resembling a folded oscillator, called the "SLIM JIM" antenna, has been widely used in the field of professional communications. The thin J-shaped antennas of amateur communication are also favored.
This "Reduced Oscillator J-Type Antenna" is shown in the figure. Its characteristics are: the radiation elevation angle is extremely low, about 0 ~ 10 °, with a gain of 3dB, twice the antenna, because the antenna itself has a matching function, it can be directly connected to a 50Ω coaxial cable.
Information shows that the horizontal 5/8 wavelength GP antenna of the SLIM JIM antenna is much stronger, which shows that its advantages are very obvious. In order to test the transmission and reception performance of this antenna, the author installed a folding vibrator J-shaped antenna on the roof of the house. When the position of the feed point is measured by a standing wave meter when the electrical point is about λ / 8 from the lower end, the standing wave ratio is about 105 (applicants must actually measure the position, which is very important for communication in the 150MHz and above frequency bands in the city, When using this antenna with a 150MHz 3W mobile phone, it can reach the outskirts of 20km. Although there are many interference from paging stations, its communication is reliable. In order to test its DX performance, the TK-708 25W power output is used. The HAM in Nanjing is the QSO, and the other party will give the RS notice. Due to more interference and the influence of the climate during the day, the probability of QSO is relatively less. The above experiments prove that the production, installation and commissioning of the J-type antenna equivalent to the vibrator are better than the GP type antenna. It is simple and has high efficiency. It should be noted that some HAMs use a plastic hard tube to protect the antenna after installing the antenna. However, due to the difference in the quality of the rigid plastic tube, after the antenna is installed, it may be Will affect the standing wave ratio, please pay attention in the application.
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The characteristics of the type antenna: the J type antenna is also called the Polish antenna. Its characteristic is that the radiation elevation angle is low and there is a certain ...
A vertically polarized antenna shaped like a folded oscillator, called "SLIM JIM" ...
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