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Many netizens have made many transmission circuit boards and used many antennas, but enthusiasts always seek high-efficiency transmission antennas. The cross antenna described below is a commonly used transmission antenna for TV or radio. Can solve the problem!
A cross antenna usually refers to a horizontally polarized rotating field antenna composed of two folded oscillators. Because of its good directional characteristics and simple manufacture, this antenna is often used as an omnidirectional antenna for low-power TV transmitters. Because of the low gain of this antenna, it is mostly used for VHF TV relay stations under 100 watts.
The main structure of this kind of antenna is relatively simple. The two folded vibrators can be fixed horizontally and crosswise. The wiring is also slightly more complicated than the single folded vibrator. The picture is not very clear. The breakdown is as follows:
Note: The above picture is a schematic diagram. The length of the cable is not drawn to scale. The length of the two U-shaped cables is half the wavelength, which is shorter, and the two quarter wavelength lines are longer. .
At that time, this type of transmitting antenna was used more and the production volume was also larger. The folded vibrator was made of custom-made aluminum tubes with special specifications. Today, few people use low-power TV transmitters in the VHF band for horizontally polarized omnidirectional transmission. Of course, our company no longer has this material. As a result, the materials used to make the vibrator were changed to aluminum strips with a cross section of 10 × 3 mm. The antenna used for channels 1-5 is not strong enough, and the antenna used for channels 6-12 is more than enough. The following picture is a double-layer cross-type rotating field antenna for large villages with more than two thousand households, driven by 3W RF power.
The feeding of this antenna is more complicated than that of a single layer, the exploded view is as follows:
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