How do I avoid a ground loop?Updated 5 hours ago

Ground loops manifest when multiple paths to earth ground exist in conjunction with metallic shielded communications cable. To mitigate ground loops, several options are available. 

First, avoid the use of shielded communications cable if feasible, relying on distance for EMI/RFI attenuation rather than shielding. 

Second, for backbone cable runs between two structures, consider employing fiber optic cable. 

Third, eliminate the potential for ground loop formation at the destination structure by utilizing unshielded patch cords or termination hardware at that end. This approach dictates bonding to earth ground at a single end only, typically the origin or "head" end. 

Note: In the case of coaxial series cable, avoiding shielded cable is not an option, as all variations of coaxial communications cable incorporate the wire braid shield as part of the conductor circuit; therefore, when in doubt, bond at the head end only. 

Finally, refrain from installing an additional ground rod (referred to as a grounding electrode) in an attempt to establish a separate earth ground alongside the existing AC electrical system grounding electrode. Installing an independent ground rod without equalizing all ground electrodes is a near guaranteed method of inducing a ground loop. 

Lastly, consult a qualified electrician capable of conducting multi-point resistance testing to ascertain the presence or potential formation of a ground loop.