Get your opinions ready - another grounding question!

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by N6MST, Nov 27, 2019.

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  1. N6MST

    N6MST Ham Member QRZ Page

    But this is a specific installation question, not a "What's the best way to ground?" thread.

    Coax will exit through a homebrew pass-through panel mounted in a bedroom window. A ground connection from a copper bar mounted to the backside of my desk will also run through the panel out to point #1 (approx six feet away) and shack equipment will be grounded to the bar. Point #1 is where I am installing a small box that contains coax surge protectors (similar to what KF7P sells but I will likely build mine into a Pelican Case and mount it to a small fence post sunk into a hole with a bag of concrete) and it will also be the location of the initial ground rod.

    Point #2 is my electrical panel and is approximately 133 linear feet away when routed in the best way possible. At least the best way I can figure. I will have to snake the copper conductor under the sidewalk near #2 but I recently had a squirrel do most of the excavation for me so the dirt is pretty soft!

    So the actual question: how often do I need to drive a ground rod in along the 133 foot route? I've seen people quote the NEC saying every six feet, but I believe the actual code basically says no closer than six feet apart. But that doesn't tell me the maximum spacing I can use. Obviously, the greater the spacing the fewer rods I have to buy and bury.

    Secondary question: What errors am I making with this plan? Let's keep this civil if at all possible!

    Thanks everyone.

  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Do you have a basement or crawlspace beneath the house? If so, I'd route your coax feed line(s) to wherever your AC service drop enters the home and place your coax entry panel close to that point. You'd bond your coax shields with or without surge suppressors to your home's AC service ground right there.

    Once inside the home you'd route cables through a basement, crawlspace or even up through the attic to reach your shack. No additional ground rod needed. There's also really no reason to run the shack equipment ground bus if your rigs have modern supplies with 3 wire ground cords and even if they didn't you'd be better off running that shack ground bus to the nearest AC outlet ground rather than out the window.
    N6MST likes this.
  3. N6MST

    N6MST Ham Member QRZ Page

    No basement, house is on a concrete slab foundation.

    As for equipment grounding, one radio has a built in power supply and three-prong plug (IC-7700), one uses an Astron RS-35A (IC-7300), and one has a two prong plug (TenTec 575). So I've got both. Maybe I'll just run a wire from the back of the TenTec out the window.

  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    You don't need any additional ground wires for your DC powered rig nor your UL approved Astron power supply.

    Really the only time you need to add grounding is with vintage 120V AC equipment that was built prior to 3 wire line cords and homes with 3 wire grounded outlets. Your modern rig and power supply are fine as they are.
    Last edited: Nov 27, 2019
    N0TZU likes this.
  5. KH6AQ

    KH6AQ Ham Member QRZ Page

    "So the actual question: how often do I need to drive a ground rod in along the 133 foot route?"

    I believe the answer is no additional ground rods are required.
    KA0HCP likes this.
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    No additional ground rods are required by code.
  7. AK5B

    AK5B Ham Member QRZ Page

    Really? I thought the rule was every 16 feet for 8 foot rods between the tower or mast and the service panel ground---am I all wrong on this?
  8. KF5LJW

    KF5LJW Ham Member QRZ Page

    TRF, good job. I have something to add. You want to use a 3-Wire Power Supply for the Equipment Ground. However if using an Astron, you need to check and see Negative Output is Floating. In other words no continuity of any kind between the chassis and Negative output Terminal. You will only have to take it apart if you get a reading. Astron has a significant consistency deign flaw. You will find the Negative either Floating, Bonded to Chassis, Somewhere in between with a resistor. You want it to float. If not, fairly easy to located and fix. It does two nasty things; puts the AC Ground in Parallel with your Radio Negative Conductor, thus you are forcing DC current on your AC Ground. 2nd opens you up to all kinds of common mode noise like buzzing in audio and RFI issues. Astron is the only one with this problem. All others to my knowledge float.

    Your radio will be bonded to dirt via Coax Shield.
    AK5B, N0TZU and K7TRF like this.
  9. K7TRF

    K7TRF Premium Subscriber QRZ Page

    There are best practices, but I don't recall any code requirements for intermediate ground rods. Personally in the OPs situation I'd at least place one at the corner of the house where the bonding wire makes a 90 degree bend.
    AK5B and N0TZU like this.
  10. KF5LJW

    KF5LJW Ham Member QRZ Page

    He did say by CODE. By code there is no additional requirement because it is considered a Supplemental Ground covered by NEC 205.53. Now if we are talking about adding supplemental rods, the code only requires 6-feet between rods. There is a big difference between code requirements and design. Codes are not a how-to or DIY manual. :D
    AK5B likes this.

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