Grounding Do's Don'ts & Why Part 3

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF5LJW, Mar 19, 2012.

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  1. W1GHD

    W1GHD XML Subscriber QRZ Page

    If you're going to put the clamp on the faucet threads, put a brass blind cap on first to protect the threads.
     
  2. K7SCS

    K7SCS Ham Member QRZ Page

    I am at the point of bonding my ground rods around my shack, making a complete ground ring. What depth are people burying the bond wire?
     
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    You will not like the answer, but by code it is required to be 30 inches and 2 AWG minimum. However by definition you will not have a Ground Ring, just Bonding Jumpers between rods and there is no minimum depth requirement.

    Having said all that, for effectiveness, as deep as you can get it. At least below frost line.
     
  4. W5UAA

    W5UAA Ham Member QRZ Page

    I almost put a complete ground ring around my shack, but then I realized that would be a ground loop. The ground rings I used to install for the tactical comm stuff I used to deploy with had a ground rod in the center of the ring, wires from the center went out to the ground rods forming a ring around it, and then a ring was formed with more wires. All equipment was then connected to the center ground rod. I was about to have a ground ring with no center ground rod. So I basically have a string of ground rounds around my shack but not a complete ring. I just re-did it with #4 solid copper (buried only about 6" deep) with cadweld one-shots. No more funny RFI issues. Should be good for the rest of my life.
     
  5. KF5LJW

    KF5LJW Ham Member QRZ Page

    No it is not a ground loop.
     
    SPEEDSKATER and K0UO like this.
  6. W6KCS

    W6KCS Ham Member QRZ Page

    That's how it's done at radio vaults, a buried ring around the vault, and the vault's main ground bus is bonded to the ring. There's no "center ground rod" and the whole thing is one continuous ring.
     
  7. W5UAA

    W5UAA Ham Member QRZ Page

    KF5LJW, you're nit picking the definition of a ground loop.... it's electrically a loop. Yes, I probably know what you're going to say is a ground loop. Not going to argue. It might not cause RFI issues and it may cause RFI issues--don't know unless you try. Each installation is unique. I chose not to connect my ground rods in a circle based on my previous experience installing "ring grounds" in a military mobile tactical environment.

    W6KCS, yes, I know. And chances are the ground ring is bonded to the rebar in the concrete the building is built on at even intervals around the ring (if they're familiar with the definition of a ring ground in military installations). Again, not going to disagree with you. Again, each installation is unique.

    There are electrical codes (<- important for SAFETY) and there are accepted practices with regards to grounding systems. A grounding system is a subject of debate. And it begins with the theory of the "sphere of influence" in a single ground rod. I can say that grounding systems are a art form and depending on the experiences of the installer, you'll get different grounding systems. Some of them will work better than others.

    May your grounding systems provide years of zero reference and safety!

    Peace out.
     
  8. K7SCS

    K7SCS Ham Member QRZ Page

    KF5LJW as you noted, I am simply bonding the eight ground rods around the shack. Installed the Kf7P today, so another step further in my bonding and grounding exercise.
     
  9. KF5LJW

    KF5LJW Ham Member QRZ Page

    Excellent, keep up the good work. . Ground Rings and Radials are the best electrodes to use for RF and Lightning Protection. Don't get carried away with rods as they do not bring or add much to the party. Rods are primarily used for Power Frequencies of DC to 180 Hz. Rods are Inductively coupled to dirt, where radial and rings are capacitively coupled to dirt and lightning travels along the surface.

    Go to any commercial tower site, and very few ground rods are used. Example at ATT, VZW, T-Mobile, or honestly any of the carriers use pretty much the same design topology. A Ground Ring around the equipment shelter with either a chemical rod or standard rod placed where the AC power and coax enters (both enter roughly at the same point). A Ring around the tower, and another under the compound fence line. From the shelter ring are four radials that extend from the corners of the building to the fence corner post. Then at least 3 radials from tower ring to the shelter and fence ground rings to comply with electrical codes. Very few rods used and when used spaced far apart. With 20-foot rods requires a minimum 40 feet separation. So even if you tried to use as many as possible with the minimum separation makes it impossible to use many rods. Radio tower use them where the AC power enters.

    The reason rings work so well is because like I said lightning, or at least any you need to worry about travels the surface of the ground. Ground Rings are proven to be extremely effective lightning protection like a Faraday Cage that shunts the current around you. Ground Rings do the exact same thing, they shunt lightning current around the Protected Area. Most folks think the impedance is important, but it is not as it will be whatever it is. Makes no difference if it is 5 or 500 ohms dirt ground. The trick or art of Lightning Protection is to direct dangerous energy away from the Protected Area. That is exactly what a Ground Ring with Radials going away from Protected Area. So what is the Impedance of such a system employing Ground Ring and Radials? Don't know, don't care. It is what it is. It is the design, not the impedance.

    FWIW another trick you can use from commercial operations is proper bonding of the coax shield(s). Most hams struggle with meeting minimum code requirements of bonding the coax where it enters the shack, and may or may not use an ADU. Commercial operators bond the coax multiple times; Tower top, mid tower, where the coax breaks off the tower, where it enters the shelter on the outside, and again inside with the ADU. Works just like the Ground Ring. You are Shunting current off the coax, and directing it to where you want it to go, DIRT and away from shelter. Once the coax enters the shelter, there is so little energy left it is harmless and the ADU discharges it to safe tolerable levels. It is a rare event for a commercial operator to suffer any lightning damage despite being hit just about every thunderstorm that passes by. Some towers multiple times each storm. That is no accident.

    [​IMG]
     
    KX4O likes this.
  10. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    Looking for suggestions on lightning surge protection devices for the cable TV - internet service line entering the house near the electrical service entrance. Are there any more worthwhile devices than the "spark gap" units the cable company installs? The house wiring is the older 2 wire 120 VAC system so I am not so sure how much protection the MOV "plug in the outlet" suppressor strips afford. Looking to protect cable modem, routers, desktop PC and TV sets. FWIW the house has a flat roof and sits on a slab so upgrading the wiring in the house is not financially feasible though service entrance & subpanel were professionally upgraded to code specs.

    Thanks for reading and your time!

    Richard
     

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