Purchase knowledge of car antenna and base station antenna
Car antenna
Car antenna refers to the mobile communication antenna designed to be installed on the vehicle, the most common is the sucker antenna. Since the suction cup antenna is easy to install and place, the suction cup antenna is often used to replace the base antenna in some simple setting occasions. On-vehicle antennas have shortened, quarter-wavelength, central plus-sensing, five-eighth-wavelength, and double-half-wavelength antennas. In theory, their efficiency increases in sequence. The length also increases in sequence. Due to the limited height of the vehicle itself, coupled with the wind resistance caused by the excessively long antenna when the vehicle travels at high speed, crossing the bridge hole and entering the underground garage are all problems. Vans require shorter antennas. The shortened antenna is small and compact, and although the gain is not high, it is suitable for occasions where a concealed antenna is required. General police vehicles are recommended to install high-increasing antennas, especially in vehicles with a relatively large active area. 350MHZ high-gain antennas are mostly divided into five-eighth wavelengths in the form of induction, and are located at a half wavelength distance from the top of the antenna A plus coil. The dual half-wavelength antenna in the 400MHZ band has a high gain. Its appearance is characterized by the addition of two induction coils on the vibrator of the antenna. The five-eighth-wavelength antenna and the centrally-inducted antenna also have higher gains and are relatively inexpensive, so they are widely used. When used as a temporary fixed station antenna, you can consider using a high-gain chuck antenna. The length of the antenna does not need to be too restrictive. Since the suction cup antenna is designed according to the use environment of the car, when it is used as a fixed, a metal plate (such as iron sheet) with a radius greater than 1 meter under it will have a better use effect. Since imported original car antennas are very expensive and the advantages are not outstanding, domestic car antennas are generally selected. In the antenna selection stage, the antenna shape and gain are mainly referred to. It is recommended to choose famous brand products of large manufacturers. The parameters provided by them are more authentic and the manufacturing process is also guaranteed. If it is a bulk purchase, you can go to a professional antenna manufacturer to customize according to the frequency band used to obtain the best use effect.
Base station antenna
The base station antenna plays a very important role in the entire communication system, especially the communication station as a communication hub. The high-gain antenna can not only increase the coverage area of ​​radio waves, but also have a certain amplification effect on the received signal, which can better receive the weak uplink signal and improve the wireless communication quality between the mobile station and the base station. Generally, the base station selects a high-gain antenna. For interference, you can consider installing a narrow-band filter according to the actual situation to reduce the impact of interference. Commonly used base station antennas include fiberglass antennas, four-loop array antennas, and directional antennas.
The FRP antenna is an omnidirectional antenna with basically no directivity, which is suitable for the situation where the base station is located in the central area of ​​the communication network. Because the FRP antenna is easy to install, it is widely used in various base stations. The gain of the FRP antenna can be up to about 10db. The higher the gain, the longer the antenna. Generally, the FRP antenna with a gain of 5-6db is more competitive in length and price. The manufacturing process is also more mature and more used. In addition to the electrical performance of this type of antenna, the quality of the outer fiberglass radome also varies greatly. Some inferior products will crack in the outer fiberglass after one year of wind and sun, leading to the scrapping of the entire antenna. Some major manufacturers are famous. The FRP antenna is more guaranteed in quality.
A directional antenna is equivalent to concentrating energy in multiple directions to transmit in one direction. It has the characteristics of high radiation gain in the main direction. The Yagi antenna is commonly used. The greater the number of Yagi antenna units, the higher the gain, which is suitable for point-to-point long-distance communication and sub-stations located at the edge of the communication network. It is more suitable for the police station located in the remote area to contact the superior branch bureau. The effect of proper use will be better than the FRP antenna.
The characteristics of the four-loop array antenna are high withstand power, high gain, and adjustable gain direction. It is suitable for communication hubs (sub-bureaus and municipal offices and relay stations), but its price is relatively high. The direction of the four transmitting dipoles of the quadrupole array antenna is adjustable. When the four dipoles are installed 90 degrees apart, the antenna characteristics are basically omnidirectional. When the four dipoles are all installed in the same direction, the antenna characteristics are directional and gain in the main radiation direction improve. With its adjustable gain direction, it can better adapt to irregular service areas. If the gain of the four-loop array antenna is not high enough, consider an eight-loop array antenna, which has similar characteristics to the four-loop array but provides higher gain. Generally, the gain of the four ring array in the 350MHZ band is 8db (omnidirectional) / 10db (directional), and the gain of the eight ring array is 12db (omnidirectional) / 15db (directional).
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