【School】 how to buy weak car and transit station antennas】.

<br> <BR> <BR> car antenna car antenna is designed and installed in the mobile communications antenna on the vehicle, the most common is the sucker antenna. .Antenna placed in the suction easy, so simple in a number of occasions, often used to establish the radio antenna instead of suction cup base station antenna. .Car antenna structure has shortened, a quarter wavelength, plus a sense of the central type, five eighths wavelength, dual wavelength form of one-half of the antenna, in theory, in order to increase their efficiency, the same length of the antenna operating band .also were increased. .The vehicle itself is limited, coupled with long antenna in the vehicle when the formation of high-speed drag the road, over bridge opening, into the underground garage are the problem, so the longer the better car antenna is not generally require car antenna does not exceed 70 cm, .van class requires a shorter antenna. .Reduce the antenna size small, although the gain is not high, but the antenna is suitable for use in covert situations require. .General police vehicle is recommended to install the antenna with high gain, especially in the region is relatively large range of vehicles, 350MHZ multiple high-gain antenna is divided into five eighths wavelength add a sense of form, the top two points away from the wave of the antenna at a distance .a plus sense coil. .400MHZ band dual half-wave antenna with high gain antenna, which is characterized by the appearance of the oscillator has two plus a sense coil. .Five eighths add a sense of the central wavelength of the antenna and antenna also has a higher gain, and the price is cheaper, so widely used. .In use as a temporary fixed station antennas used the occasion to consider the sucker high gain antenna, the length of the antenna do not have too many restrictions. .Since the antenna is based on car use suction cups designed for the environment, so when used as fixed under the smoke in its radius is larger than 1 meter piece of metal plate (such as iron) will be better the results. .Since the original import car antenna is very expensive and does not highlight the advantages, it is generally used homemade car antenna. .Selection of the antenna phase <BR> main form and gain reference antenna. .Suggested the use of large factories, brand-name products, they provide the parameters of the authenticity of relatively high, the manufacturing process is also guaranteed. .If it is entirely possible to bulk purchases of professional antenna manufacturer customized by the use of frequency bands to obtain the best results. .Base station antenna base station antenna in the whole communication system has a key role, especially as the communications hub of the communication stations. .High-gain antenna will not only increase the coverage area of radio waves, but also has some of the received signal amplification, can be better to receive weak uplink signals, to improve the mobile station and base station wireless communication quality. .Under normal circumstances the base station are equipped with high-gain antenna, the interference situation can be considered according to the actual installation of narrow-band filter to reduce interference. .Common base station antenna fiberglass antenna, Victoria array antenna, directional antenna. .Fiberglass Omni Antenna for the basic non-directional antenna for base station location in the case of the central area communication networks. .<BR> The fiberglass antenna easy to install, it is widely used in various types of base stations. .FRP can reach a maximum antenna gain of about 10db, the higher the gain the longer the antenna, usually a gain of 5-6db gain antenna length of glass and steel prices more competitive, more mature manufacturing processes, using more. .In addition to electrical properties of such antennas, the outer layer of fiberglass radome there is a large difference in quality, some low-quality products in the wind and the sun outer glass after one year the situation will result in cracking the whole antenna, scrapped, a number of brand-name manufacturers .FRP more secure in the quality of the antenna. .<BR> Directional antenna is equivalent to the direction of the energy is concentrated more than one direction up to the launch, the main direction of radiation with high gain characteristics of commonly used Yagi antenna. .Yagi antenna, the more the number of cells the higher the gain, long-distance communication and for point to point edge in the sub-station communication network used. .More suitable for targeted police stations in remote areas, contact with the superior branch used, used properly the effect will be better than the fiberglass antenna. .City of Victoria to bear the characteristics of the antenna array power, high gain, gain adjustable direction for communications hub (as well as relay stations and Urban stations) to use, but its price is relatively high. .<BR> Ring oscillator array antenna transmitting direction of the four adjustable, when the 90-degree intervals of four oscillator installed base for the omni-directional antenna characteristics, when all four oscillator installed in the same direction with a directional antenna characteristics, while in the main .radiation gain increased. .The direction of use of its adjustable gain feature can better adapt to the irregular service area. .If the Ring Array Antenna gain is not high enough to consider eight-ring array antenna, which features a similar array, but with the City of Victoria provides a higher gain. .Victoria General 350MHZ frequency gain matrix 8db (omnidirectional)  10db (orientation), a gain of eight-ring array 12db (omnidirectional)  15db  orientation)..