Can't bond ham shack ground to service entry ground

Discussion in 'General Technical Questions and Answers' started by AE0AQ, Mar 6, 2018.

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  1. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    A rural house fire can put many nearby residences in jeopardy if the forest or grass ignites as a result, especially given the long response times and limited resources of rural fire districts.

    My shorts are quite comfortable, thanks!
     
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    When I installed my tower there was no requirement for me to bond it to my electric service.

    The path of least resistance is the theory that I went by. That is one reason that I made all of my coax lengths longer than my grounds for my lightning protectors.

    Lots of ground rods at the base of the tower and entrance point works for me. :)

    No need to disable my repeater or needing to disconnect coax during a lightning storm.

    To each his own. Be safe not sorry.

    Have Fun. Flame on...
     
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    That was never a theory and never taught. Anyone who says that needs to answer: what happens if you have 2 unequal resistors in parallel? Say a 1 and 4 ohm resistor. There is only one correct answer and enough information is provided to answer. 80% of the current flows through the 1 ohm resistor and 20% through the 4 ohm resistor.
     
    KA9JLM likes this.
  4. K8MHZ

    K8MHZ Ham Member QRZ Page

    Thanks for taking the time to bring this to Mr. Holt's attention and reporting back here. Also thank him and the other moderators for their time.

    Most of all, thanks for your many hours here on QRZ working with us. I consider your 'stickys' to be a fantastic resource for grounding radio stations. Is there an 'e=book' in the future?
     
    N0TZU likes this.
  5. K8MHZ

    K8MHZ Ham Member QRZ Page

    That has been an NEC requirement for a long, long time. Now, it may be true that when you installed your tower, your jurisdiction did not require you to follow the NEC.

    The importance of bonding is the same, no matter if required by gavel or not. After a thread about it on Mike Holt's forum with a poster reluctant to agree, I changed my avatar.

    [​IMG]
     
    KA9JLM likes this.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    If you have 100 foot of coax and 50 foot of coax connected to a T, and feed a signal into it, What coax is going to get the signal at the end first ?
     
  7. K8MHZ

    K8MHZ Ham Member QRZ Page

    I am lost as to how the above pertains to equipotential bonding.
     
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    Steve let's back up again. Remember 810.3? That coax thingy. Coax rules fall under 820.

    Keeping that in mind, 810 is addressing Twin Lead, Ladder Line, and Open Wire systems. Now I do stand corrected, there is no requirement to use ADU's on coaxial or Twin Lead systems. However there is a requirement to bond the shield as close as possible at the point of entry 820.93 & 820.100

    So how does one do that? For you and I working with 1-5/8 inch Hard Line and Wave Guide is strip the insulation off the shield and use an Andrews Grounding kit. Ham and CATV uses a Grounding Block because they use smaller coax with a braided shield as a matter of convenience. As N0TZU stated a better method is to combine the Ground Block and ADU into one device and kill 2 birds with one shot.

    Bonding the shield gives you projection from nearby strikes and shunts stray currents and voltages (aka noise) to earth. Does nothing for the center conductor and a direct strike. If lightning strikes the antenna, the fault is on the center conductor and has already found its way to earth. Either through your house wiring via radio, or ADU directly to earth. An ADU also does something else commonly over looked. It discharge static charges that build up. Now in reality with an ADU unless you have a properly configure Single Point Ground, any surge protector device has Voltage Let Through. As a result some fault current will flow into the radio and find its way to earth through the green ac wire on the power supply and/or Grounded Circuit Conductor. So the job of the ADU, TVSS, SPD or whatever name you want to give it is a Shunt. The ADU will Shunt the vast majority of fault current to dirt while keeping the Let Through to acceptable levels. Unfortunately ADU's and lightning are not created equal. Get a hot enough strike on a small ADU, you get a fried radio and house wiring. There is only so much you can do.
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    Just a example of the path that a lightning strike would take to dissipate the energy.

    First come first served. :rolleyes:
     
    Last edited: Mar 13, 2018
  10. W6KCS

    W6KCS Ham Member QRZ Page

    OK, here we go, I'm going to stand up on my chair now.

    This is where I get screwed up. For the longest time, due to 810.3, I assumed that ham (or commercial or anything else) stations using coax needed to go to 820 for the requirements for installation such as shield bonding. I said that here back about ten pages ago and get a bunch of pushback saying 820 is for cable and 810 is for hams, and then another guy says getting rid of the ground rod is "bogus" even though that ground rod does nothing but tie the radio chassis to ground and nowhere else, not the rest of the ground system, not the coax, not the tower, nothing, it's just a probe in the ground ready to equalize step potential through the poor guy's house wiring.

    Then I read this: "Short story is what I said earlier, If a TX is involved, only 810 applies"

    Then this: "Coax rules fall under 820"

    And a bunch of other stuff going back and forth. So if I seem like I'm not quite getting it 100% of the time, that is the reason. That is why I asked if I was required to use an ADU or just a shield bond. Because if it's just a bond, and that requirement comes from 820, then at least some parts of 820 apply to our coax installation even though it says that the scope is cable TV and satellite.

    KA9JLM, lightning takes all paths.
     
    Last edited: Mar 13, 2018

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