Single Point Grounding 4 Dummies

Discussion in 'General Technical Questions and Answers' started by AI5DH, May 18, 2020.

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page

    Many of us know plenty. Ohms Law is old school. Us old farts know it well. :)

    It is not all about who can win a contest ? Like you make it out to be. o_O

    upload_2020-5-25_18-27-54.png
     
  2. AI5DH

    AI5DH Ham Member

    What are you talking about? Who would do that?

    Look you have a big misunderstanding of what I am saying. The Choke I speak of is not between the Antenna and Earth Ground anymore than your DC Power Supply is. Perhaps that is why we are so far apart. You do not understand Single Point.

    Lets say the offending Ground Wire is the DC Power Supply AC Equipment Ground wire. The one in the AC Power Cord, going back to your AC Branch Panel Board. Understand? There are two ways to fix it..

    1. The Ugly way. Take a big Snap-On Ferrite Core and wind the AC Power Cord as man y times as you can.

    2. Use a Manufactured Common Mode AC Line Filter inside the DC Power Supply or use a Power Supply with built-in already like a good lab quality supply If you have one of the Newer Astrons, you can use the filter below by replacing the AC Receptacle on the back. A simple $15 mod and fix.

    [​IMG]

    Just like your DC Power Supply, your Station Ground is just another Equipment Ground inside your shack. You Coax Shield, AC Ground and Station Ground all come from the same point outside. This is not hard to understand or vision. A single wire ground wire not capable of conducting any current other than AC and DC. It is not in between your Antenna and Earth Ground. It is an Open Circuit once it enters and goes no where. Once a Circuit enters the house, it never sees earth again.
     
    Last edited: May 30, 2020
    KA9JLM likes this.
  3. AI5DH

    AI5DH Ham Member

    You keep asking the same question over and over again. It is not hard to find NEC 250.2. and 250.4 It is not buried, advocation, or an option. It is required.

    250.2 Effective Ground-Fault Current Path. An intentionally constructed low-impedance conductive path designed to carry fault current from the point of a ground fault on a wiring system to the electrical supply source.

    250.2 tells all electrical equipment must have planned Equipment Ground. Hams use a lot of passive electrical equipment like Tuners, Bridges, and Coax Switches. Those are Required to have a Equipment Ground and that comes from your Station Ground. Coax cannot be used and coax is not a Ground.

    250.4 (3) (3) Equipment Bonding. Metal parts of electrical raceways, cables, enclosures, and equipment must be connected to the supply source via the effective ground-fault current path.

    250.4 (3) is Crystal Clear.

    As for Mike Holt, TRY THIS. It will spell it out for you explaining in great detail. It cover 250.1 to 250.6

    On Mike's Forum, DIY are not welcome and cannot join. You must be in the Trade with credentials. Most of the MOD's like myself sit on Code Making Panels of NEC. Look at Mike's Drawings, same ones used in NEC. The very second someone shows contempt and ignorance for electrical codes , are toast never to be seen or heard from again.

    So why do you have contempt for codes? I understand most of the rest peanut gallery, , but not you.
     
  4. WA7ARK

    WA7ARK Ham Member QRZ Page

    Yes, the choke is between the antenna and earth ground. This has zero to do with single-point grounding, line filters, or DC supplies.

    In designing, building and deploying LF/HF antennas, there are many cases where it is desirable to block common-mode on coax cables, both during transmit and receive. The best way to do this is to place a common mode choke on the coax that looks like this:
    [​IMG]

    A not-so-good way to do it looks like this:
    upload_2020-5-30_6-55-35.png

    Suppose you have a horizontal wire antenna held aloft by trees. Suppose that to prevent RFI being conducted toward the antenna from inside the house during receive (or to prevent CM RF current from entering the shack during transmit), you add such a choke. The coax/radio gear is properly bonded to earth near the house...

    The choke has almost zero DC resistance through it (so it drains static charges as carried by rain drops or snow grains or blowing dust) accumulated by the elevated wire. It has a high RF impedance end-to-end (that is its job).

    So what happens if the antenna wire is struck by lightning?
     
    N0TZU likes this.
  5. W9WQA

    W9WQA Ham Member QRZ Page

    i dont think lightning has a conscience
     
  6. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    Another insult, like “Charlie Brown” I see.

    In fact I strive to conform to codes. If I didn’t care, I wouldn’t have asked a question.

    But I get it - if someone questions a statement of yours and asks for a code reference then they are labeled as contemptuous of code.

    Apparently I made it too subtle for you. I should have just come right out and said I think you’re wrong instead of politely asking a question intended to allow you to clarify, or gracefully backtrack.
     
    Last edited: May 30, 2020
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  7. KA9JLM

    KA9JLM Ham Member QRZ Page

    The NEC is not God.

    It is a recommendation. o_O
     
    KA0HCP likes this.
  8. K6BRN

    K6BRN XML Subscriber QRZ Page

    OK. What happens when a coax is struck by lightning between the antenna and entrance ground block? Had this happen once at my CT lake house. So here is just one real possibility.

    1. The coax jacket was blown off in random patches and charred along the feed line wherever there was a nearby conductive surface, 2. The internal dielectric was melted and blown away at random intervals with the shield and center conductor fused together at points, 3. The center conductor and shield "ceased to exist" for about six inches, 4, the ground block (with internal protection circuit) was blown OPEN circuit, though the outside looked just fine, 4. The overall feed line, what was left of it, became "brittle" and could easily be broken into pieces, 5. The connected tube equipment at the receiving end, which had emitted a fine example of ball lightning that scared the cr@p out of me and my kids and XYL smelled pretty bad and part of the cabinet was charred. But it still worked.

    Coax was RG-59. Connected equipment was a TV - solid state/tube hybrid.

    A previous poster is right - lightning is very fickle. Unless you have an industrial strength lightning strike suppression system built directly into the building and antenna, what exactly will happen when any part of the building or antenna/feedline is struck is not terribly predictable. And there are many strengths and a couple of different types of lightning strikes (negative and positive strokes/single stroke or multi-stroke) - no two ever seem to be the same.

    Brian - K6BRN
     
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  9. WR2E

    WR2E Ham Member QRZ Page

    Dreck, if you have so much obvious contempt for the unwashed masses of hammy hambones in the peanut gallery, why do you bother?
     
  10. K6BSU

    K6BSU Ham Member QRZ Page

    How can there be so many questions on SPG?

    It's pretty straightforward.

    People should not rely on QRZ.com for their basic electrical education. First, read the applicable text books. Then, and only then,
    post your questions on QRZ.com. Most members here are not professional educators, so explaining a simple concept might be
    a real chore for some, even though they understand it.
     

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