What are the external antenna selection criteria?

　　First, determine the device signal coverage area and determine the signal coverage direction based on the antenna radiation pattern. Antennas are divided into omnidirectional antennas and directional antennas based on the antenna radiation direction.

　　(1) External omnidirectional antenna

　　An omnidirectional antenna is an antenna that radiates uniformly in 360° on the horizontal pattern, which is what we usually call non-directional.

　　Suction cup antenna

　　The gain is relatively large. The biggest feature is that it has a strong magnetic suction cup, which is easy to install and fix. However, the suction cup must be adsorbed to a metal surface. In the wireless module industry, suction cup antennas are often used in conjunction with wireless modules to increase the communication distance of wireless modules, such as smart meter reading, vending machines, express lockers, and car radios.

　　Copper rod suction cup antenna

　　Similar to the ordinary whip suction cup antenna, but the advantage over the whip suction cup is that it uses a pure copper radiator with a larger diameter, which has low ohmic loss, high antenna efficiency, and wide bandwidth coverage. It is suitable for data radio stations with relatively high performance requirements, medium-distance image transmission, etc.

　　Rubber stick antenna

　　The most common external antenna, with moderate gain and relatively low price, is commonly used in wireless communication modules, wireless routers, data transmission radios, etc. The antenna size can be selected according to the installation space requirements. The antenna size is related to the gain. Generally, the longer the length in the same frequency band, the higher the gain.

　　Fiberglass antenna

　　Among omnidirectional antennas, fiberglass antennas have the best performance. Its inner core is a pure copper vibrator, it uses balanced feeding, and is less affected by the environment. The outer shell is made of high-quality fiberglass, has good three-proof properties, and is well adapted to harsh natural environments. It is particularly suitable for ultra-long-distance gateway signal coverage, image transmission, etc.

　　(2) External directional antenna

　　Generally used in environments with long communication distances, small signal coverage ranges, and high target density. Extreme examples include point-to-point long-distance communication.

　　Flat-plate antenna

　　High efficiency, small size, and easy installation. It can consider the effects of gain and radiation area at the same time. It is suitable for indoor and tunnel wireless signal coverage; medium-distance signal transmission, image transmission, and signal penetration through walls.

　　Yagi Antenna

　　This antenna has very high gain, is slightly larger in size, and has strong directivity. However, careful attention to the antenna's orientation is required. It can be used for ultra-long-distance signal transmission, image transmission, and direction finding.

　　Log-Periodic Antenna

　　This ultra-wideband antenna offers very wide bandwidth coverage, reaching up to 10:1. It is commonly used for signal amplification, indoor distribution, and elevator signal coverage.