About Arrestor

In general, a surge means a voltage which is increased 5~6% or more comparing the normal or a impulse signal upto a few thousand volt with very short time (ns, us, ms terms). For example, there is a momentary overvoltage, is occurred at power switch on/off situation or lightning. If the surge is flowed into the circuit, semi-conductor chip and the transmission lines could be burned out. The performance of whole system is tended to be degraded, and it is caused fatal breakdown. It is quite nuisance in RF circuit.
Most of products have protection circuit, such as varistor, zenor diode or tantal, to prepare the surge occurred at connection parts with connectors. However, it is still not safe for the outdoor repeater or base station which is connected with the jumper cable from the antenna from the lightning. Moreover, the antenna is tend to draw the lightning so that the repeater and base station(BTS) is quite weak at lightning. Then the arrestor is required to protect them.
Where we should install the arrestor? If you are in system integrating business, you should pay attention. Let’s see the example for the BTS.
Under the picture, the arrestor is installed ahead position to protect the green equipment and GND is connected the earth. If you look at the picture carefully, there are the power line from the power source and cable line from antenna. It means that the arrestor should be connected with all of each lines, such as power line, signal line and communication line.

Gas Discharge Tube (GDT) and λ/4(Air type) type of arrestors are used. The GDT type of arrestor is mostly used. The arrestor which is insulator (10GΩ) as close as an infinite, does not do any function as usual, but the spark gab is terminated if the momentary overvoltage surge or lightning is flowed through lines. There is the electric charge carrier in discharge area in the gas tube arrester, when the spark gab is terminated the electric charge is moved into the electron in fast. The high accelerated electrons are collided with gas molecule and the electron is separated from the gas molecule. During this procedure, the momentary surge by rapidly increased electron carrier is flowed fast.
The energy by momentary surge is rapidly flowed to earth through an effective grounding so that the equipment can be protected safely. The surge voltage is varnished and the charged electron is recombined to the gas molecule. When the gas tube arrestor is burned out, the gas tube capsule or gas tube arrestor itself should be changed for the next protection.