Lightning Surge Protection for Coaxial Cable Networks

Lightning Surge Protection for Coaxial Cable Networks

Coaxial Cables Lightning Protection

Nearby lightning strikes usually generate a short duration high current (thousands of Amps) pulses. These impulses contain components with very diverse frequency ranges i.e., both low and high frequency. Typically, the VHF and UHF components can be picked by outdoor communication antennas leading to generation of very high voltages and currents.


Fig 1: Gas Discharge Tube Lightning Protection Device


Generally, the strike creates a potential difference between the center conductor and the cable shielding of the coaxial cable. This then forces a high voltage differential and damaging current flow through the equipment. A lightning surge protector is therefore needed to shunt this very high current to the ground without transferring it to the connected devices.

Fig 2: Connecting LSPD to the Coax cabling

It is important to note that these are not direct strike devices but only handle the effects of nearby strikes. In the event of a direct strike your protection device would most likely be permanently damaged.

What to consider for Coaxial Lightning Surge Protector Devices (LSPDs):

·           1.  RF Performance

This covers the operational frequency, insertion loss and VSWR. These parameters will indicate what portion of the transmitted signal will reach the output and what portion would be lost during transmission. The goal is to keep the losses low, thus low values of VSWR and IL are ideal. Typically, the surge protector primarily operates as a passive component during most of its lifetime only coming into action in the event of surges.

·            2.   Connector type (for instance N, TNC, SMA etc.)

In most cases protectors offer bidirectional protection, meaning you can reverse inputs and outputs without affecting operation. Connectors bring different designs for both the inner and outer conductors; usually the outer conductor has a significantly greater current capacity than the center pin to help dissipate the surge current. The current rating of most center pins is rated as the survivability of ten 8x20μs ampere pulses. 


Connector Type






Pin Diameter






Transient Current Capacity (Higher limit)






Transient Current Capacity (Lower limit)






Table 1


Of these connectors, each has an inherent maximum voltage, current, and RF power limitations due to the physical design and materials used.

·               3. DC pass/ DC block protector

Indicates whether the connector allows or blocks DC power to equipment alongside the RF signal. If equipment is to be powered, you need DC power through the center pin of the COAX cable to connected devices.

·               4. Type of technology

There are two dominant technologies in surge protection:

Gas Discharge Tubes (cost effective and very common, derate over time usually about 5 years; can build static electricity over time which can cause equipment damage when discharged)


Fig 3: Replaceable Gas Discharge Tube with Screwable Unit to Secure onto LSPD


Coil inductor (offer reliable protection to surges, do not degrade over time but need replacement with significant lightning strikes, no static build up, usually more expensive than GDTs) 

·             5.  Type of Mount and connection to grounding:

Configuration of the protector can be used to make it easier to mount, connect and ground successfully. The connection to ground must also be perfect to ensure all the harmful surges are passed to ground. For outdoor applications waterproof units with rubber seals are required.


Simply put when selecting a LSPD go for one with the:

  1. Lowest insertion loss and VSWR for the frequency of operation
  2. Largest recommended connector type for longer service
  3. Maximum Transient Current Capacity so as to carry the highest possible spikes in currents
  4. Best Bi-directional Protection Level
  5. Convenient mount and connection to ground depending on location of installation.

 For more information and custom design solutions for protecting your wireless networks contact us here or give us a call on +1 480 218 1877 or +1 410 877 6887.

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