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Thread: ground rods

  1. #1

    Default ground rods

    The dirt around my home is very hard. I can't get an 8 foot ground rod pounded in.
    Will two four foot ground rods work just as well?
    Thanks!

  2. #2
    Super Moderator 5B4AJB's Avatar
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    It may work better.

    There are a lot of factors to consider for an R.F. earth.

    Try loosening/softening the ground with a hosepipe for a few days before you try inserting it.

    I used 1" copper pipe in hard clay in London, pouring water in every day and knocking it down a little, it wasn't 8' long but I did get a few feet in.

    Lidl were selling 3' drillbits for concrete a while back, with hindsight, I should have bought one for this - maybe you can rent a hammer drill with one for the day?

  3. #3
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    the purpose of most 8 foot ground rods is to reach sufficiently moist soil level
    that layer can usually be found between 4 to 6 feet beneath the surface. water itself may conduct current but not very much.
    it is the mineral content or impurities of the water that conducts electricity ( as an experiment try conducting electricity in a glass of sterile water then do the same experiment in a glass of sterile water with a couple tsp. of salt dissolved in it.)
    or measure the resistance with a vtvm.

    ive always found a demolition hammer( small electric jackhammer) will drive a ground rod very quickly! or soak the ground very good before driving the rod.
    too much blood in my caffeine system.

  4. #4

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    Thanks for the feedback!

    I asked about ground rods because Iím setting up a new station after moving. I reviewed the code and suggestions from several other hams, and Iím a little confused because of some
    contradictory information.

    My HF antenna is a dipole strung between two metal poles. One is mounted to the side of my house and is used only to support one end of the dipole. The other pole is mounted to a wood fence and supports the other end of the dipole and a 2m vertical dipole antenna,

    All antenna coax will enter the side of the house via a metal box, and grounding blocks will be used in the box on all the cables. There is a ground rod next to the box. This ground rod will be connected to the box, and also to the A/C ground at the service entrance. So, everything entering the shack will be grounded to the box before they enter the house. The box will be grounded to a ground rod, which will be connected to the other ground rod at the fence pole and
    To the ground at the A/C service entrance.

    Here are the questions:

    I have read in more than one article that ground rods arenít necessary outside the shack, that you should just connect to the ground wire going to the A/C entrance. One article states that ground rods outside the shack is dangerous. Is this true?
    I plan to ground the metal dipole support pole with the 2m antenna on it with a ground rod, but do I need to ground the pole that acts as a support only?
    When I connect the grounds together and the A/C service ground, what size copper wire should I use? I have heard that #6, #8, and #10 are the required gauge, depending on who you ask.I plan on routing the copper through the crawl space under the house, a distance of about 40 feet.
    I plan on running a ground wire from the outlet I am using in the shack to the metal box outside. This has been recommended from a couple of sources and seems to make sense, but others say you shouldnít do this. Is this recommended?

    I realize that there are a lot of different options on station grounding, and I appreciate any input
    you guys may have.

    Thanks!

  5. #5
    Super Moderator 5B4AJB's Avatar
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    Multiple earth points will naturally generate a small Voltage between them, which your radio will pick up.

    If the R.F. field density is high, the induced Voltage is higher meaning more noise to the receiver.

    All your earthed equipment should be tied to the same earthing point to reduce this.
    The earth straps from the equipment to the earth point will pull in noise, but keeping them short as practical will reduce this as much as possible.

    I wouldn't use the AC ground for an earth, it's going to have a ton of random noise on it already.
    40 feet of earth conductor is pretty much worthless unless it's vertical, try to find the closest route to ground you can, even if it means drilling a hole in the shack floor.

    So, to summarise, your path to earth should have as low a resistance as possible, if you could drill a mile wide copper rod to the centre of the earth and bolt your radio directly to it, that would do, the resistance of the copper would spoil your efforts, but if you cooled it down like a superconductor, it would help a bit...

  6. #6

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    Quote Originally Posted by 5B4AJB View Post

    40 feet of earth conductor is pretty much worthless unless it's vertical......

    According to the code, I need to bond my ground to the A/C entrance ground, right?

  7. #7

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    I agree with 5B4AJB in that you should avoid using the AC mains ground. So many problems can occur. All that wire in the wall can act as an antenna and the loops can resonate. You will be picking up the noise from all your electronics in the house, any DSL noise on the adjacent phone lines and any RF that happens to pass through the house ~ along with any circulating currents in the ground wire loops due to resonance. Things can be further complicated due to poor wiring practice. For example, when there is a main panel and sub-panel, it was a common mistake for DIY'ers and professionals alike to connect the ground with the neutral in the panels. This is a big problem because the return current can take two paths to the main panel ~ through the neutral wire and also through the ground rods between the sub-panel and main panel. This often sets up an AC voltage anywhere from a few millivolts to several volts, situation depending (which also electrolyticallty corrodes the rods). Long story short, just don't use the AC mains ground. That code book wasn't written for amateur radio.

    I also recommend getting a dedicated ground rod pounded down as deep as possible as close to the radio as you can.
    Last edited by brandon lind; Wed 7th Oct 2020 at 16:40.

  8. #8

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    Quote Originally Posted by brandon lind View Post
    Long story short, just don't use the AC mains ground. That code book wasn't written for amateur radio.
    Ok, so I put a ground rod as close to the radio as possible, but I don't run a wire from that ground rod to the A/C entrance ground, and
    I don't connect the ground rod to the A/C ground in the shack, right?

  9. #9

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    Correct. A dedicated ground rod with the shortest possible run of ground strap for your radio stuff is ideal.

  10. #10

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    But if I understand correctly, now the ground potential is different between the mains ground (your kit) and the station ground (the aerial). I thought the point was to have everything at the same potential, to avoid having a strike pulse from coming back in the house?

  11. #11

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    Quote Originally Posted by WZ7U View Post
    But if I understand correctly, now the ground potential is different between the mains ground (your kit) and the station ground (the aerial). I thought the point was to have everything at the same potential, to avoid having a strike pulse from coming back in the house?
    That is my understanding and why I started this thread. So far, the only confusion is whether to run a bonding wire from the ground rods to the A/C entrance panel ground.

  12. #12
    Super Moderator 5B4AJB's Avatar
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    The A/C panel should have its own earth rod - if you do have to connect them together, try using a fusible resistor in series (1W) of, say 1MΩ.

    Nothing is going to protect you from a direct lightning strike, massive Voltages will be induced everywhere, even if the cables are disconnected and several metres apart.

    As a project, solder a (few) small neon bulb across a coax socket, disconnect your coax from the radio and connect the neon, watch it dance!

  13. #13

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    Quote Originally Posted by 5B4AJB View Post
    The A/C panel should have its own earth rod - if you do have to connect them together, try using a fusible resistor in series (1W) of, say 1MΩ.

    Nothing is going to protect you from a direct lightning strike, massive Voltages will be induced everywhere, even if the cables are disconnected and several metres apart.

    As a project, solder a (few) small neon bulb across a coax socket, disconnect your coax from the radio and connect the neon, watch it dance!
    Good suggestions, Thanks!

  14. #14

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    Grounding advice is often confusing because there are many grounding requirements and it can be difficult to meet them all at the same time. The primary requirements for grounding are:

    • Electrical service safety
    • Lightning protection
    • Static charge dissipation
    • RF counterpoise

    And probably more.

    The NEC covers the electrical service safety and states that all services entering the building must be bonded to the building service ground. This is to protect the people inside the building in the event of a fault that energizes the ground. If you were to come between an appliance connected to the electrical ground, say your computer, and an appliance connected to the antenna ground such as your radio the fault current could pass through you and could be fatal.

    If you are not running AC out to your antenna, the antenna itself may not be covered under the NEC rules, but if there is an electrical fault in your house or in the service feeding your house and you are holding the unconnected coax connector in one hand and the independently grounded tower in the other hand... Basically you need to treat any independently grounded conductor as if it were energized with the line AC.

    While you cannot always stop lightning from coming in, it is possible to direct it and minimize the potential damage. Commercial radio and television stations are designed to take a direct strike. For the best surge protection you want to insure that all connected systems rise with the surge at the same time. The basic rule is that all conductors enter at a common point where they have a common ground and protection to limit the voltage on non-grounded conductors.

    For your radio setup there will be several of these common ground points: at the point where the feedlines enter the house they would connect to a ground rod bonded to the house ground thus creating the first sphere of protection. The point where the feedlines, AC power and other utilities enter your shack or the corner of your room where all the equipment is connected together creating a sphere of protection for the operator and equipment. Note that any conductor exiting this sphere and connecting to a different ground point can create the potential for a differential surge voltage that is damaging to the equipment and users. And each piece of equipment would have its own internal common ground point to protect the sensitive components inside.

    A static charge can build up on any conductor that is exposed to blowing dust or snow. This is most effectively dealt with by having all the antenna elements dc grounded. 1/4λ stubs, baluns etc. can add a dc ground. Most radios will have some internal protection. But think about how you are going to remove the coax in bad weather. When you pull that connector from the radio, you become the path to ground.

    Sometimes you can get RF in the shack even when everything is grounded. If your shack is on an upper floor and itís a quarter wave length down the ground line, to RF that looks like an open circuit. In some situations you may need to create an RF ground by running radials from your shack ground. In most cases it would be better to deal with unbalanced feedlines at the antenna end before the RF gets back to your shack.

    ó Dan O. [N0BAF]

    And sorry for the length. I didnít intend for this to be a full length article but there is so much to say.

  15. #15
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    good point and info!
    as a commercial electrician I have often performed earth resistance tests in preparation for installing ground electrodes.
    although its been said its not related to radio it actually is important.
    while having a ground rod is important you must have a low enough resistance to be safe electrically.
    bonding any metal object be it a tower, radiator, metal water pipe (any metal object that you may come in contact to) brings all theses thing to an equal potential.
    and yes there can be a lot of electrical potential difference in buried metal objects even a few feet apart depending on soil composition and its moisture content
    even in the chemical composition of the metal! (prime example: zinc coated nail and a piece of copper wire stuck into a potato or orange) ( you have a battery)
    too much blood in my caffeine system.

  16. #16

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    Quote Originally Posted by DanielW999 View Post
    Grounding advice is often confusing because there are many grounding requirements and it can be difficult to meet them all at the same time. The primary requirements for grounding are:

    Electrical service safety
    Lightning protection
    Static charge dissipation
    RF counterpoise

    And probably more.
    Yes, it is confusing, but I understand a little bit more about it now. I will run a ground wire to the A/C entrance that connects my shack ground wire and my antenna grounds. I realize that this won't protect my equipment from lightning, but it will help protect people in my house from shocks due to surges from nearby lightning strikes, and I will be in NEC compliance.
    Thanks for the info!

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