Ground Strap or Ground Wire

Discussion in 'General Technical Questions and Answers' started by STDYIN, Sep 6, 2020.

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  1. KA0GKT

    KA0GKT Ham Member QRZ Page

    That's why I also wrote "A flat wide copper strip has a smaller impedance than a round conductor with an identical cross section."

    A 6" wide, 0.003" thick piece of copper strip has a cross section of 22.918 MCM or about the same cross section as a 7AWG wire. A 6" wide .098" thick copper strip has a cross section of 748 MCM, 4/0 cable is 250 MCM. 4" wide by .003" has about the same cross section as 8AWG wire Copper strip comes in numerous gauges in between these two extremes and in widths as wide as 12" (on special order) and smaller.

    Just as you correctly stated, "the voltage is just a product of high current flowing through an impedance..." any reduction of the impedance reduces the EMF while the current remains the same so a large cross section conductor is needed to handle the current. This can be achieved along with low(er) impedance with a wide, thin (flat) conductor. This is why copper strip is often found in the grounding systems of commercial facilities.
  2. AI5DH

    AI5DH Ham Member

    John lets turn you into a ground guru in 5 minutes or less. There is absolutely nothing complicated about it. Once you see it , you will understand it. Then you will kick yourself for trying to make it complicated. What you are about to see is exactly how all commercial and professional operators do. It is detailed in many publications and standards like:

    •ANSI J-STD 607B
    •ANSI/NECA/BICSI 607:2011
    •ANSI/TIA 607B: 2011•
    *BICSI TDMM 13thEdition:2014
    •BS 7430:2011
    •IEEE 1100:2005
    •IEEE 81:2012
    •ISO/IEC 30129:10.2015•
    NFPA 70:2014 (NEC)
    •Motorola R56:2005
    •ARRL Grounding and Bonding for Amateur Radio

    Just to name a few. Ground must be a Single Point and there can only be 1, count them, ONE GROUND and ONE GROUND ONLY. The real simple thing is you can put Ground just about anywhere you want. You can put it in a basement, ground floor, second floor of a house, or on the roof of a 100 story building. Where you want it to be. Ground is NOT DIRT, it is a point anywhere referenced to dirt or something in place of dirt like a car chassis or a ham sandwich. The only requirement is the ground be located on an outside wall inside the shelter where both coax, AC Power, and all outside cables enter.

    So take a look below, magic happens, you instantly understand what is going on. Current has to have a complete path in order to flow. Current must have at least 2 Nodes to flow, it must have an entry point node, and an exit point node. Otherwise current cannot flow. So now take a close look. The heavy vertical black line can be a tower or coax shield. The Green Ground Symbol is your Ground Electrode System aka Earth Ground in Euro's. Any outside currents are not allowed to flow through any of you radio toys. There is no path through it.

    John as you already know because you have made it already, Single Point Ground is implemented by using a Equipotential Ground Plane. You used a 12' x 16" x 1/8 sheet of C110 Copper as your entry panel. Ground cannot be a piece of wire or pipe with equipment grounds connected willy nilly. There would be too much impedance between connection points. It needs to be a plane thick enough to withstand and fault current imposed through it. You use that plane to mount all Antenna Discharge Units, reference your AC Ground to which you did by using a Power Term Strip, and equipment grounds. You put all the PRODUCERS (coax ADU's/Sheilds and AC Equipment Ground) on one half of the plane and the NON PRODUCERS on the other half of the Plane. The ABSORBER cable aka Ground Electrode Conductor goes in the middle separating the two zones. When segregated that way, if a Producer like a Coax, AC System, CATV or TELCO produce a fault, the Fault Current is not run across your EQUIPMENT GROUND PLANE on the other side of the PLANE producing potential voltage differences. Neither you or the equipment is exposed to the fault current.

    It does not matter what the Earth Impedance is, or how long the cable is going to the Ground Electrode System. If can be 1000-feet above the dirt on top of a sky scrapper. It will be whatever it is going to be. What is important is there is a PLANNED FAULT PATH to Earth capable of withstand the current imposed upon it with no potential differences between equipment units. Additionally no other incidental or unplanned paths exist for current to flow. Ground must end exactly where it begins. No way for current to enter and exit out.

    Now look at the CORRUPTED or MULTI-POINT GROUND. This is what just about every Amateur does. You have invited all outside currents to come right in and flow through your radio equipment. In fact you will have common mode current flowing 100% of the time. Key the mic and you will have a lot of common mode current flowing through all equipment grounds guaranteed. You forced it on there on purpose. You intentionally made it do that. How does it happen? Real simple, your DC Power Supply or anything with an AC power cord ground put you between two Earth Electrodes. You no longer have a Ground of any kind. Instead of your radio being an open circuit dead end connected to a single point, is now a piece of wire some 20 to 50 feet long. The wire starts at your AC Service Ground via the branch circuit and enter the DC Power Supply Chassis , Since you failed to pull out the bonding jumper inside the DC PS, the DC Negative is doing double duty as an Equipment Ground to a radio designed for a car electrical system has it chassis bonded to negative. From the radio your chassis ground is now a coax shield doing a job it is not suppose to do going to outside on the coax shield to Earth Again. Can you say Daisy Chained Ground Loop? Each piece of your radio equipment is connected to a different point along a length of wire with current running through it at all times where there should be no current. That means every piece of your radio toys is at a different potential or Reference Point. No wonder you got RFI and EMI. You made it that way.

    Simple to fix. You move all Grounds to a single point so there is no voltage potential between any two pieces of equipment. When you plugged in your power supply, linear amp, or AC Powered gizmo. you failed to move the AC Ground and placed your radio between two earth potentials. It really is that simple.

    Last pair of drawings is a commercial design showing the most common corruption of a SPG I have seen and witnessed many times. Same effect, different cuase. Comes down to incompetent installer who failed to isolate equipment racks from the building structure. They fail to put isolation pads under the equipment racks, and/or isolation bushing on floor anchor bolts. The racks make contact with the concrete which is a Earth Ground. Real simple to find, just ask which rack got hit and look at the floor where you will find the burn marks. Find the installer and make them pay for damages and repairs.


    STDYIN and KB0MNM like this.

    STDYIN QRZ Member

    so ANYTHING plugged into my Branch 120V power outlet
    Mainly the Trip Lite Power strip

    so ANYTHING plugged into my Branch 120V power outlet
    (that is Inside my SPG Box Outside, the Branch line also running around the house outside along with my ground line)
    Mainly the Trip Lite Power strip should have this plug
    the plug being grounded to the SPG-Plate and nowhere else
    the branch line should NOT be grounded to the SPG-Plate
    as its Grounded at the Main power panel

    Screen Shot 2020-09-08 at 2.03.56 PM.png
  4. KB0MNM

    KB0MNM Ham Member QRZ Page

    Essentially, that is correct. The wire to your single-point ground which continues through the circuit-breaker box then out to the branch circuit would be a longer one than what you could attach nearer the S.P.G.
    However, there might be some concerns if the following are present: ground-fault circuit breaker or arc-fault circuit breaker in the circuit breaker box, or ground-fault circuit interrupter outlet at the branch termination.
    If the branch circuit has already been wired, it will very likely have the 'round' connection for 'ground' below the line and neutral sockets. Some would say that a new circuit should be wired with that 'round'/'ground' above each set of blade sockets, yet that may not be consistent with other outlets in your home. Irregardless of that 'detail': you would be better served by one wire to the S.P.G., than a loop of two 'grounds'. I am certain that KF5LJW will comment on this.
    Remember that the U.P.S. would provide power with the circuit breaker/G.F.C.I./A.F.C.I. open, thus defeating the open circuit with the 'ground lifter' device in your illustration would not occur. For that, you would need a G.F.C.I. after the U.P.S. as a separate module. It would need to reference the neutral and S.P.G. If you are providing lighting from the other half of the branch circuit, there would be no need to 'lift' the 'ground' as you might desire for the U.P.S., yet a G.F.C.I. module might be added for safety on that circuit ( provided the physical spacing of the outlets would permit that to co-exist with the 'ground-lifter' for the U.P.S. ).
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    My SPG in the van is the chassis of the van.:)
  6. K8DO

    K8DO Ham Member QRZ Page

    Nyaa, you are all a bunch of poseurs (pronounce that carefully ) :D
    My "real" SPG ground point behind the radio bench is a two foot by six foot sheet of aluminum screwed to the wall (which is plywood) All grounds are short wires to the sheet using large sheet metal screws that self-tap through the metal and into the wood securing them tightly. Vastly quicker and easier to hook/unhook than fiddling with nuts and bolts and lock washers while hanging over top of the gear (and trying not to knock half the stuff off onto the floor). . The plate has a short 2-0 welding cable (maybe a foot long) that is drilled straight through the wall to an 8 foot ground stake immediately outside the wall. That stake has bare conductors under the soil surface that go to the tower and other ground stakes forming a grounding grid.
  7. K8DO

    K8DO Ham Member QRZ Page

    My SPG in the van is the chassis of the van.:)

    So, how big are the drag chains grounding the van? :p

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