Dec. 23, 2019
Theoretically, the ideal installation position of the vehicle-mounted satellite antenna is the center of the roof. The antenna is attracted to the roof by a magnetic suction cup. Although it is usually insulated from the metal roof, there is no difference between the two. The small capacitance forms a path at high frequencies, and the roof of the car is used as the ground network of the antenna feed system, which together with the antenna forms the antenna system of the car radio.
There are four indicators that determine the performance of the antenna of the car radio: maximum power, center frequency, bandwidth gain and standing wave ratio. In general, the first indicator does not need to be considered, because the maximum power of the car radio antenna is more than 100W, which is much larger than the maximum transmission power of the car radio. The last three indicators are closely related to each other. The center frequency refers to the optimal resonance frequency when the antenna is working. If it works at this frequency, all the transmission power of the car platform will be converted into electromagnetic waves by the antenna and radiated out. The standing wave ratio is 1 (ideal state), and the off-center frequency standing wave ratio will gradually increase. When the standing wave ratio gradually increases to 1.5 (power reflection reaches 4%).
The width between the upper and lower frequency points is called the working bandwidth of the antenna. The bandwidth depends on the external form of the antenna, manufacturing materials, quality factors, and gain. The higher the gain, the narrower the bandwidth, which will exceed the frequency band.) The effective transmitting power and receiving sensitivity will decrease sharply. When the standing wave ratio is greater than 2 (power reflection reaches 11.1%), it is recommended to stop the vehicle's transmitting work, otherwise the equipment safety will be endangered. The center frequency and bandwidth gain of the car antenna are fixed after they are manufactured in the factory, and they are usually clearly marked on the packaging or nameplate. However, the standing wave ratio of the antenna is uncertain, and it is also closely related to the actual installation location of the antenna. The car satellite antenna is the latest invention, and his effect is particularly good. The location must be installed correctly!