Lightning Arrestor Types
A gas discharge tube arrestor contains a tube of gas connected between the center conductor and the shield. The gas tube acts as an on/off switch. When the potential difference across the tube is high enough, the gas is energized and turns “on,” shorting the center conductor to the shield, and allowing the current to flow to ground. When the voltage falls back below the turn-on threshold, the gas tube turns “off,” allowing the coaxial cable to operate normally.
Gas discharge tube arrestors do not provide a path to ground for DC and low frequency components. They allow static electricity caused by wind and precipitation to build up in non-DC grounded antennas. This static causes noise. When the static voltage exceeds the turn-on threshold of the gas tube, the gas tube will turn on, shunt the static charge to ground, and turn off again, but then the cycle will repeat over and over.
Whenever the gas tube turns on, some discharge can reach the radio, especially if the arrestor is non-DC blocking. Some commercial radio manufacturers strongly recommend against gas discharge tube arrestors.
The gas in a gas discharge tube arrestor has a limited number of energized cycles. If the gas tube is repeatedly energized, such as to eliminate a build-up of static electricity in the antenna, the arrestor can become degraded over time and will not adequately protect the equipment when needed.
An inductor-type arrestor uses a high current inductor between the shield and the center conductor. The inductor effectively grounds DC and low frequency lightning components, while allowing the desired RF frequency range to pass through.
Inductor-type arrestors will bleed off static electricity that can build up in non-DC grounded antennas. Some inductor-type arrestors also include a gas tube to provide even more current-carrying capability for high-surge events.