[Photo] J-shaped antenna with folded element

A vertically polarized antenna resembling a folded oscillator, called the "SLIM JIM" antenna, has been widely used in the field of professional communications. In the amateur communication experiment, this thin folded dipole J-shaped antenna was 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, and the efficiency is twice that of the λ / 4 GP antenna. Because the antenna itself has a matching function, it can be directly connected to 50Ω coaxial cable. Information shows that the horizontal radiation intensity of the SLIM JIM antenna is much stronger than that of the 5/8 wavelength GP antenna. It can be seen 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. Measure the position of its feed point with a standing wave meter, and find that when the feed point is about λ / 8 from the lower end, its standing wave ratio is about 1? 05 (applicants must actually determine the position, which is very useful for communication at 150MHz and above important).
In the city, when the antenna is used with a 150MHz 3W mobile phone, it can reach the suburbs at 20km. Despite a lot of interference from paging stations, its communication quality is quite reliable.
In order to test its DX performance, 25W power output of TK-708 was used. In the evening, it can be used as QSO with HAM in Nanjing, 80km away, and the other party gave RS-55 ～ 56 report. During the day, due to more interference and the impact of climate, the probability of QSO is relatively less.
The above experiment proves that the production, installation and debugging of the J-type antenna with folded element are simpler than that of the GP-type antenna, and the efficiency is higher. It has practical value for V / UHF amateur communication. The author thinks it is worth promoting. It should be noted that some HAMs use a plastic tube to protect the antenna after installing the antenna. This is of positive significance. However, due to the difference in the quality of the rigid plastic tube, when it is placed on the antenna, it may affect the standing wave ratio, please pay attention to it in the application.

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[Photo] J-type Antenna

A vertically polarized antenna shaped like a folded oscillator, called ...

Published on 2006-04-15 21:08 • 583 times read
[Photo] J-type Antenna
[Photo] Various J-shaped antennas

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 ...

Posted at 2006-04-15 21:07 • 969 views
[Photo] Various J-shaped antennas
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