A surge arrestor (or surge protector) is a small device installed in the cable of an antenna that prevents a voltage surge to reach equipment attached to the antenna (such as a router). It does not prevent damage to the antenna from lightning. Rather, it protects the equipment to which the antenna is attached.
Most antennas use Gas Discharge Tube (GDT) type arresters. There are 2 versions of GTDs:
Economy – single strike
Premium – multi-strike
When do you need a surge arrester?
Usually surge protectors are requited in a fixed site antenna installation, where the antenna is:
Located above the roof line.
In an exposed location.
In a multi-site occupancy where the site owner mandates surge protection.
The area is more susceptible to lightning (e.g. Singapore/Hong Kong).
Sometimes surge arresters are required mobile antenna installations where:
The vehicle operates in a hazardous area.
Surge protection is mandated by the customer or specific region.
How a surge arrestor work?
An arrestor is installed on the cable(s) coming out of an antenna. One surge protector is required per cable. When there is a lightening incident, the device discharges or shunts the high voltage surge to ground. As such, the arrester body must have a low resistance connection to ground.
Each arrestor has a GDT fitted between inner conductor and the arrestor body, but does not conduct under normal conditions. However, under high voltage surge, the GDT conducts and provides a low resistance path to ground, diverting the surge from reaching the equipment.
What happens if lightning does strike an antenna with surge protection?
The antenna may or may not operate after a lightning strike. However, the equipment attached to the antenna likely will remain in operation.
Depending on the type of surge protector, the impact of the surge may be different.
Single Strike (or Economy) Arrester – the arrestor may need to be replaced. This is because the GDT may not return to a non-conductive state.
Multi-Strike Arrester – the GDT recovers and reverts to being non-conductive and therefore should not have to be replaced.
What happens if lightning does strike an antenna with surge protection?
Most likely, the antenna will not operate after a lightning strike. However, the equipment attached to the antenna likely will remain in operation.
Depending on the type of surge protector, the impact of the surge may be different.
Single Strike (or Economy) Arrester – the Arrestor may need to be replaced. This is because the GDT may not return to a non-conductive state.
Multi-Strike Arrester- the GDT recovers and reverts to being non-conductive and therefore should not have to be replaced.
What is a serge arrester?