ChatGPT: Will a grounded lightning arrester block common mode current on the coax shield?

Assume I have a ham radio that is rated for 100 watts output. Also assume I have a lightning arrester that connects the coax shield to a ground rod. Will this connection to earth ground block common mode current returning from the antenna?

Connecting a lightning arrester to earth ground does provide a path for lightning-induced currents to dissipate harmlessly into the ground, thus protecting your equipment. However, when it comes to common mode currents on the coax shield, the situation is a bit different.

Common mode currents are those currents that flow on the outside of the coax shield (instead of the signal-carrying center conductor) and can cause interference or damage to your equipment. While grounding the lightning arrester will provide some level of protection by diverting lightning-induced currents, it might not necessarily block all common mode currents.

In the scenario you described with a ham radio rated for 100 watts output, the primary purpose of the lightning arrester and its grounding is to protect your equipment from surges caused by lightning strikes. To address common mode currents, additional measures may be needed, such as using common mode chokes, baluns, or ferrite beads on the coaxial cable to suppress unwanted currents.

While grounding the lightning arrester is a good practice for overall equipment protection, if you are specifically concerned about blocking common mode currents on the coax shield, you may need to consider additional measures beyond just grounding the lightning arrester.