How Antennas Work
An antenna is an energy converter that converts the guided wave propagating on the transmission line into an electromagnetic wave propagating in an unbounded medium, or vice versa. The lower the frequency, the longer the wavelength and the longer the antenna. Generally, antennas are reversible, that is, the same antenna can be used as both a transmitting antenna and a receiving antenna, and the basic characteristic parameters of the same antenna as transmitting or receiving are the same. For example, the antenna is applied to the wireless device to transmit the electromagnetic wave signal output by the wireless device or to transmit the electromagnetic wave signal received by the antenna back to the wireless device.
Antenna selection
There are many types of antennas, such as FPC antennas, short glue stick antennas, long bendable antennas, suction cup antennas, satellite TV receiving antennas, and plate antennas. First, select the antenna according to the structural size of the product. For example, if the structure of a wireless product is very limited, you can only consider placing the antenna in the casing, then you can only choose FPC soft antenna or short glue stick antenna, or even directly integrate the antenna on the PCB board (make it a PCB antenna) ; If the size of the product is not limited, you can choose a suction cup antenna or a glue stick antenna with high gain and larger size, and the relative transmission effect will be much better; if you are using it in satellite TV, you can use a dedicated satellite TV Receive antenna. Of course, the choice of this antenna is not fixed, and it needs to be selected according to its own needs.
Antenna matching
What is matching? Matching means that the load impedance connected to the feeder terminal is equal to the characteristic impedance of the feeder. When the antenna is applied to a wireless device, matching is equivalent to matching the output impedance of the wireless device with the input impedance of the antenna, or the input impedance of the wireless device and the antenna. The output impedance is matched. The input impedance of the antenna is the ratio of the input voltage to the input current at the feed end of the antenna. The best antenna will be made into a standard 50 ohm, and the impedance of the wireless device is also a standard 50 ohm. In this way, the antenna and the wireless device are completely matched, ensuring that there is no The loss of the transmission signal, thus ensuring a good communication effect.
Selection of position
1. The installation site should be far away from metal conductors that absorb and reflect radio waves. This can prevent effective electromagnetic wave signals from being effectively absorbed, resulting in a decrease in transmission efficiency;
2. Avoid the influence of trees and buildings on the antenna;
3. Keep away from electric light wires, telephone wires or tram transmission lines, and absolutely not parallel to them, which will affect the electromagnetic wave signal;
4. Try to install the antenna away from the car and pass through many roads to avoid the influence of electromagnetic waves on the vehicle equipment;
5. Do not install near the user's TV antenna, FM receiving antenna or amateur radio antenna, thereby causing mutual interference;
6. When installing a fixed directional antenna, directivity must be considered.
Wind and lightning protection treatment
Antennas are generally higher to facilitate long-distance communication, so lightning protection and wind protection are also very important. The wind resistance of the wire antenna is generally not large, as long as the installation mast has sufficient strength and is fixed with a stay rope, there is generally no problem. Regarding lightning protection, if there are taller buildings nearby and lightning rods are installed, as long as the lightning protection device is within the 45° angle cone, it can receive lightning protection protection. But if your antenna is the highest, you should install a lightning rod, and it is recommended to disconnect the antenna from the radio and connect to the ground during lightning.
Waterproof treatment
Since the antenna is erected outdoors, it is recommended to use silicone rubber for waterproof treatment on the exposed part of the antenna, otherwise the antenna is easy to oxidize and cause poor contact.
Periodic adjustment and maintenance
The antenna generally needs to be adjusted and overhauled every three months, so the convenience of disassembly should be considered. So it is better to install pulleys on the mast.
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