Antenna Grounding Advice

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KJ6EWX, Feb 12, 2018.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    The coax is required to be bonded before it enters the building. Otherwise you defeat the purpose.
  2. KJ6EWX

    KJ6EWX Ham Member QRZ Page

    Yes I would do that. I meant that the bond wire would have to go back to the opposite side of the house through the wall and garage.
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    OK my bad. Not ideal and I would not do it that way.
  4. KJ6EWX

    KJ6EWX Ham Member QRZ Page

    Roger, and thanks for all your help!
  5. K8MHZ

    K8MHZ Ham Member QRZ Page

    Read EC&M with a grain of salt.

    "Ground rods spaced less than two rod-lengths apart will interfere with each other because their effective resistance areas will overlap (Fig. 2a above). For reference, see IEEE-142 and Soares Book on Grounding. The overlap increases the net resistance of each rod, making the grounding electrode system less effective than if the rods were spaced farther apart..."

    Read the above carefully.

    The overlap will make the system less effective than if the rods were spaced farther apart, but it does not make the system less effective than if the additional rod was not present. Adding a rod within the sphere of influence of another rod does not increase the net resistance of the entire system.
    N0TZU likes this.
  6. K8MHZ

    K8MHZ Ham Member QRZ Page

    That may be true in best practice, but I don't see that specified in the NEC. 810.21 allows for several places of connection, but nothing says it must be done before the coax enters the building. One allowed point of connection is the grounded interior metal water piping system. 820.100 (B) (2) (2) for instance.

    In fact, 810.20 even allows ADU's to be inside or outside the building.

    What many fail to understand is that the NEC is a MINIMUM set of standards, and is NOT meant to be a design manual. See 90. (C)

    Just because 'code allows it' doesn't make 'it' the safest installation, nor the best or efficient. Actually, an installation done exactly 'to code' is the worst installation allowed by law.

    Some jurisdictions make additional requirements to the NEC, while others remover them. For instance, the State of Michigan does not enforce Article 547, nor does it enforce the NEC requirement for AFCI protection in one and two family dwellings.
    N0TZU likes this.
  7. NH7RO

    NH7RO Ham Member QRZ Page

    Hope someone corrects me if I'm wrong but running that bonding wire through one's house is dangerous at best---doing so welcomes the path of a lightning strike right into one's home!

    I don't know much of the NEC but I bet it states somewhere that all ground rods and bonding between them must be completely external, right?
  8. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Unfortunately not. There are allowances for internal ground rods or grounding structures like Ufer grounds as part of the building's foundation or cold water mains grounding which is still permitted in some places.

    But I'm with you, I'd run that bonding line around the perimeter of the building and not straight through it. Actually I'd probably stick with the original plan for the coax run and do the coax bonding right at the existing service entry ground or on to a bonded ground rod on that side of the building.
    NH7RO likes this.
  9. K8MHZ

    K8MHZ Ham Member QRZ Page

    I'll take that bet.
    NH7RO likes this.
  10. NH7RO

    NH7RO Ham Member QRZ Page

    OK, thanks, guys---now I know better---thanks for the clarification.

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