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Vertical ZL- Beam Antenna for 430- MHz

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ANTENTOP- 02- 2010, # 014

Vertical ZL- Beam Antenna for 430- MHz

 

 

 

Vladimir Polyakov, RA3AAE, Moscow

Credit Line: HF- magazine, 1998, pp.: 27- 31

(published in Russian in Moscow).

 

I would like to make a simple directional

antenna. After I had observed lots

variants I stopped at ZL- beam with two

elements with active feeding. The

antenna looked very attractive for me.

This one at its small sizes (only

lambda/8… lambda/10 in length) was

practically the same parameters as 3-

element YAGI.

 

Figure 1 shows a simple design of the ZL- beam. Points X-X is the feeding terminal of the antenna. ZL- beam consists of two dipoles (simple or folded) that connected together by crossed wires. Depending on the length of the fires the dipoles fed by some phase shift that helps form the diagram of directivity. (Note by I.G.: More about ZL-Beam see References 1 and 2)

Figure 1 ZL- Beam

 

Required phase shift between the

antenna’s elements are obtained by two

ways. At first, it needs change the length

of the crossed line. The second, (it is

fine tuning) by changing of the length of

the dipoles. If the tuning may be made

then no matter at which points at the

crossed line would be connected feeder

of the antenna.

Usually ZL-beam is used as antenna with horizontal polarization i.e. the dipoles are placed in parallel to ground. That is because of the simplicity of that antenna design. 

I decided to make antenna with vertical placement of the dipoles to ground. For the antenna’s  element should be suitable J- Antenna. (Note by I.G.: More about J- Antenna see References 3 and 4). Figure 2 shows two version of that J- Antenna. Version of the antenna with the grounded stub (right at the Figure 2) is mostly suitable for my design. It is possible to connect  the lower point of the grounded stub with any ground- roof of the car, metal mast and so on. It is possible to match the antenna with any coaxial cable by choosing the feeding points.

 

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