As an important part of the communication system, the antenna performance directly affects the indicators of the communication system. So the user must first focus on its performance when selecting antennas. Specifically, there are two aspects. First select the type of antenna; Secondly, select the electrical performance of the antenna. The significance of selecting the antenna types is whether the selected antenna pattern meets radio coverage requirements in the system design; the requirement to choose the antenna electrical performance is whether the choice of wifi antenna frequency bandwidth, gain, rated power and other electrical indicators are in line with the requirements of the system design. Therefore, the users best contact manufacturers for consulting in the choice of antennas.
What is the voltage standing wave ratio?
When the characteristic impedance of the antenna input impedance and the feedline is inconsistent, the reflected wave and the incident wave stack on the feeder and generate magnetic wave, the ratio of the maximum value and the minimum value of the adjacent voltage is the voltage standing wave ratio, which is the basis to test feeder transmission efficiency. If the VSWR is less than 1.5, the voltage standing wave ratio is less than 1.2 in the working frequency and the voltage standing wave ratio is too large, it will shorten the communication distance, and the reflected power will be returned to the transmitter power amplifier section, which is easy to burn out the amplifier tube, affecting the normal work of the communication system.
How to select the cable and the length of the cable
The mobile communication systems often use characteristic impedance of 50 ohm coaxial cable as a feeder. In order to effectively transmit the radio waves to the antenna interface, you should minimize the transmission loss of the feeder. The transmission loss depends on the cable diameter and length. In the same frequency, the larger the cable diameter, the smaller the loss is; the longer the cable, the greater the loss. In principle, it requires that the transmission loss of the cable should not be more than 3 db. The following table lists commonly used cable attenuation value (db / m), users can reasonably select the cable type and length according to their own circumstances.
How to install antenna and feeder systems?
First, assemble the antenna, feeder and supporting parts according to the requirements of the product description, and then fix with the fixture at the yagi wifi antenna support position in pole antenna support, and make the antenna and pole parallel spacing to be greater than the use of wavelength, reducing the influence of the pole to the performance of antenna. In the antenna port place, connect the feeder (or say cable head) and antenna with connector, bend a diameter of about fifty times the feeder diameter ring and fix in antenna support, avoid connector parts direct stress to be broken or damaged.
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