Effective installation method of horizontal dipole antenna

The antenna has hundreds of unique horizontal dipole antennas (DIPOLE ANTENNA), simple and economical, and high efficiency.
The standard impedance of a horizontal dipole antenna is 73 ohms. Figure 1 shows the standard setup method. The antenna elements are aligned in a straight line, and the pillars on both sides can be replaced with buildings or other rods such as bamboo poles. When the radio frequency of your radio equipment is low, if you want to set up a standard horizontal dipole antenna, you must set it up on a wider surface. This is the biggest limitation of the city. However, it is not necessary to make a standard horizontal dipole antenna, but it can also be driven into an inverted V shape (as shown in Figure 2), so that the area length can be saved a lot, and only one central pillar is needed.
The relationship between the angle of the horizontal dipole antenna and the impedance is 73 ohms when the angle of the feeder of the horizontal dipole antenna is 180 degrees; from the angle of 180 degrees, the impedance will gradually decrease. 68 ohms at 150 degrees, 58 ohms at 120 degrees, 50 ohms at 105, 42 ohms at a narrower angle of 90 degrees, and 23 ohms at 60 degrees.
Therefore, if a 50-ohm coaxial cable is used as the transmission line of the antenna, an angle of 150 degrees is the most ideal. Figure 3 is a comparison of the height of the horizontal dipole antenna from the ground and its impedance.
From this graph, we can see that when the angle of the horizontal dipole antenna is the same and the height of the antenna is not the same, there may be situations where the impedance is different. For example: when the opening angle of your horizontal dipole antenna is 120 degrees, the height of the antenna above the ground is 0.56 wavelength, 0.73 wavelength, 1.15 wavelength (in the case of 21MHz, it is 7.95 meters, 10.37 meters, 16.33 meters). The impedance has dropped to 50 ohms.
If you want to set up a set of highly efficient horizontal dipole antenna, you must pay attention to the above items. Other than that. Special attention should also be paid to the following items: antenna elements should be avoided as close as possible to Dianhua wiring and power lines.
If the surrounding of the antenna body is too close to the general wire, it will not only affect the impedance of the antenna, but also cause radio wave interference. The distance above one wavelength is the most ideal. If the two cannot be balanced, please try to avoid the antenna element and the wire parallel, and use a high one low or cross each other. In the case of reinforced concrete buildings, steel, and other metals, it has the same effect, so please pay special attention.
The use of balanced and unbalanced converters (BALUN) The horizontal dipole antenna itself is balanced (BALANCE) but the coaxial cable is unbalanced (UNBALANCE). Guangdong welcomes the unbalanced cable line balanced antenna At this time, you need to use balanced and unbalanced converters, but the price of QI is generally higher than the price of a set of homemade simple dipole antennas. In this case, it is also possible to use the converter, as long as the above matters It can be noticed that there is no problem in actual use.
When adjusting the horizontal dipole antenna, you can first hang the top of both ends of the antenna element about 30 cm, and then cut the length of about 3 to 5 cm at a time until the standing wave ratio while watching the standing wave ratio table. At the lowest, this is one of the simplest adjustment methods.
When setting up an inverted V-shaped horizontal dipole antenna, the most important thing is to pay attention to personal safety issues. Because when the radio is transmitting, the horizontal dipole antenna itself will generate a high-frequency current, and the high-frequency voltage at both ends is the strongest. Therefore, if you want to erect this antenna, please try to erect it in a place where people can't touch it, so that it is safer, or please mark the danger notice sign.

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