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"Gary Schafer" wrote
It doesn't matter what you want to call a ground conductor. The point here is if it can carry any lightning current you are much better off with it buried in the ground. A bare ground conductor making contact with the soil acts like additional ground rods. Why would you not want that? Burying coax feed lines will help with lightning protection. It greatly increases the inductance of the lines to lightning. It also helps to dissipate the energy to ground by the coupling provided. (ie you get less at the other end) You can't help but view them as "grounding electrode conductors" as you may want to call them. After all they are connected to the tower. They are going to carry lightning current if you want them to or not. Might as well let them dissipate part of the energy to earth. A large part of the lightning is RF. You have to treat it as such. A good lightning ground also makes a very good antenna ground system. ( buried radial system) Think in those terms. 73 Gary K4FMX Hi Gary, the coax feedlines are definitely NOT grounding electrode conductors. Not only are they incapable of such by design and accordingly not authorized as grounding conductors, but they could never remain connected to sensitive equipment if it were so. Neither is the shielding on coax sufficient to provide equipotential bonding so they are not allowable bonding conductors either. If anyone wants to sacrifice their coax by not properly shield-grounding and installing the appropriate number of coax lightning arrestors (this means on the tower also) then they will turn them into very ineffective grounding conductors. Burying might help then, but only because you could guarantee a breakdown in the dialectric and where safer to have that happen than underground. I understand many operators allow this and simply toss them out the window, or ground them before a storm, but there is no good reason for it. Proper installation can allow them to remain connected to the equipment without sacrificing the coax or the equipment. Burying coax does not prevent induction by either capacitive or magnetic induction onto the shields of the coax from a nearby strike. If coax were enclosed in metal conduit that was grounded at each end, there would be protection from this. But proper installation of shield grounding and surge suppression at both ends maintains safe levels of energy on the feedline and allows its connection to sensitive equipment.Of course in rare cases there is sufficient energy (such as a 200Ka+ return stroke current) to overcome any level of protection. But protected stations will certainly fare a lot better in those rare events than the unprotected ones. 73, Jack Painter Virginia Beach VA |
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