Local communication / communication with amateur relay stations in urban areas, it is generally possible to use short and light small antennas, because the interference in urban areas is relatively large, small antennas are not easy to be disturbed, and a smaller gain has little impact on the use of relay. on the contrary, it can make the signal more clear and stable, at the same time, the small antenna is not easy to scratch low objects. 

A longer antenna can be used for direct communication between suburban vehicles, which can increase the communication distance between vehicles. 

At the same time, the antenna should be selected according to different models, so that the antenna can be coordinated with the shape of the vehicle after installation, play a decorative role in the car, add highlights to the appearance of the car, and choose a longer antenna for the car. for off-road vehicles, you can choose the antenna with thick and wild points. 

vehicle mounted antenna. 

The vehicle antenna refers to the mobile communication antenna designed and installed on the vehicle, and the most common is the sucker antenna. 

Because the sucker antenna is easy to install and place, the sucker antenna is often used instead of the base antenna in some simple situations. 

In the structure of vehicle antenna, there are shortened antenna, 1/4 wavelength antenna, middle sensing antenna, 5/8 wavelength antenna, double 1/2 wavelength antenna and so on. Theoretically, their efficiency increases in turn, and the length of the antenna in the working frequency band also increases in turn. 

Due to the limited height of the vehicle itself, coupled with the wind resistance formed by excessively long antennas when the vehicle is moving at high speed, crossing bridges and entering underground garages are all problems, so the vehicle antenna is not as long as the better. the car antenna is generally required to be no more than 70cm. Vans require shorter antennas. 

The shortened antenna is small in size and low in gain, but it is suitable for use in situations where concealed antennas are needed. 

General police vehicles are recommended to install high-increase antennas, especially in vehicles with large activity area. 350MHZ high-gain antennas are mostly divided into the form of 5/8-wavelength induction, and there is an induction coil at the distance of 1/2 wavelengths from the top of the antenna. 

The dual 1/2 wavelength antenna in the 400MHZ band has a high gain, and its appearance is characterized by two inductance coils on the vibrator of the antenna. 

Five-eighths of the wavelength antenna and the middle inductive antenna also have higher gain and cheaper price, so they are widely used. 

The sucker antenna with high gain can be considered when it is used as a temporary fixed station antenna, and the length of the antenna does not need to be too limited. 

Because the sucker antenna is designed according to the environment of the car, it will be better to absorb a metal plate (such as iron sheet) with a radius of more than 1 meter when it is used as a fixed. 

As the imported original vehicle antenna is very expensive and the advantage is not prominent, so the domestic vehicle antenna is generally selected. 

In the stage of antenna selection, the shape and gain of the antenna are mainly referred to. 

It is recommended to choose famous brand products from large manufacturers, the authenticity of the parameters they provide is relatively high, and the manufacturing process is also guaranteed. 

If it is a batch purchase, you can go to the professional antenna manufacturer to customize according to the use frequency band, in order to obtain the best use effect. 

Base station antenna. 

The base station antenna plays a very key role in the whole communication system, especially the communication station as the communication hub. 

High-gain antenna can not only increase the coverage area of radio waves, but also amplify the received signal to a certain extent, which can better receive weak uplink signals and improve the quality of wireless communication between mobile station and base station. 

In general, high-gain antennas are selected for base stations. In the case of interference, narrowband filters can be installed according to the actual situation to reduce the impact of interference. 

The commonly used base station antennas are fiberglass antenna, four-ring array antenna and directional antenna. 

The FRP antenna is omni-directional, which is suitable for the situation that 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 all kinds of base stations. 

The maximum gain of FRP antenna can reach about 10db, and the higher the gain, the longer the antenna. Generally, the FRP antenna with 5-6db gain is competitive in length and price, and the manufacturing process is more mature and widely used. 

In addition to the electrical performance of this kind of antenna, there are also great differences in the quality of the outer FRP radome. After some inferior products are exposed to the wind and sun for a year, the outer FRP outer layer will crack and cause the whole antenna to be scrapped. Some famous brand FRP antennas in large factories are more guaranteed in quality. 

Directional antenna is equivalent to concentrating energy from multiple directions to transmit in one direction, and has the characteristics of high radiation gain in the main direction. Yagi antenna is commonly used. 

The more the number of elements of Yagi antenna, the higher its gain, so it 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 police stations located in remote areas to contact superior sub-bureaus, and the effect of proper use will be better than that of fiberglass antennas. 

The four-ring array antenna is characterized by high power, high gain and adjustable gain direction, so it is suitable for communication hubs (branch and municipal bureaus and relay stations), but its price is relatively high. 

The direction of the four transmitting vibrators of the four-ring array antenna is adjustable. When the four vibrators are installed 90 degrees apart, the antenna characteristics are basically omni-directional. When the four vibrators are all installed in the same direction, the antenna characteristics are directional, and the gain in the main radiation direction is increased. 

The use of its gain direction adjustable characteristics can better adapt to irregular service areas. 

If the gain of the four-ring array antenna is not high enough, the eight-ring array antenna can be considered, which is similar to the four-ring array but provides a higher gain. 

In general, the gain of the 350MHZ band four-ring array is 8db (omni-directional) 10db (directional), and the gain of the eight-ring array is 12db (omni-directional) "15db" orientation.