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. KI7HSB

    KI7HSB Ham Member QRZ Page

    Dereck, I really appreciate your posting these articles... I'm currently designing my first HF station and need all the help I can get!
     
  2. KF5LJW

    KF5LJW Ham Member QRZ Page

    Let me know if I can help.
     
  3. KF4ITA

    KF4ITA Ham Member QRZ Page

    No transmitter, a receive only station.
    I'm building a BOG antenna and using Cat6 cable with a shield for my feed line.
    The feed line is 230ft long. I'll have ground rods at the antenna where it meets the feed line.
    And ground rods at the entrance to the house. My question, do I want to make a connection at both ends
    to the ground rods.

    If I do that, Is that asking for current flow in the shield?

    Should I just make the ground connection at the house only?
    Not sure how to proceed.
    Mikek KF4ITA
     
  4. W3TDH

    W3TDH Ham Member QRZ Page

    I have been retired for over 5 years now and I no longer keep up with the latest edition of the US National Electric Code (NEC). The last addition that I have here at home has a section 250.52 (A)(6) which reads "
    (6) Other Listed Electrodes. Other listed grounding electrodes shall be permitted." Were do I find reference to radials in the NEC?
     
  5. KG5IFY

    KG5IFY XML Subscriber QRZ Page

    Forgive my ignorance, I'm sure as a licensed operator I should be more knowledgeable on this, but here we are...

    My home's electrical panel is in my garage, with the ground rod directly outside. My shack is on the other side of the home. I'm running an end-fed antenna right now. I don't understand how I'm supposed to properly ground my antenna and station to my home's panel ground.
     
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  6. W1GHD

    W1GHD XML Subscriber QRZ Page

    My Inverted L is terminated at the corner of my property, with the coax direct-buried to my entry panel. The coax for my dipole comes down on the opposite corner of the house; it is also direct-buried to the entry panel. My VHF/UHF antenna coax is routed there as well.

    My Polyphasers are mounted in the entry panel and bonded to the electrical service ground. All cables enter the basement at this point and route into my shack.

    With proper planning, it can be done. Use good quality coax, and you can add the length needed without performance issues on HF frequencies. My LMR-400 is overkill on HF, but it can be direct-buried and there is virtually no loss in the extra length needed to set up a proper ground system.
     
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  7. W3TDH

    W3TDH Ham Member QRZ Page

    W1GHD has provided one good answer and there are others. If you bring all of your antenna leads in at the location closest to your electrical service's first enclosure then it is very easy to bond the Electrical Grounding Electrode System to the Antenna's Grounding Electrode/s. From experience doing electronic shelters for communications in many different places I would strongly suggest that you have more than one Grounding Electrode protecting the Antenna Lead In.

    The basic rule of thumb is that if you are using driven rods you should drive them twice their own length apart. With 8 foot rods that is 16 feet apart. You drive the first rod it's own length from any structure which extends into the earth. The most likely of those is the portion of your basement wall which extends underground. The footer of that wall will extend another foot below the inside depth of the basement wall. So if your basement's depth approaches half of it's height into the earth come out from the basement wall 8 feet. If your electrical service is mounted on the side of the home your side yard may well be less that 16 foot wide but that is not a problem because you wouldn't have been going straight out from the wall any way. You can go out at an angle to a point 16 feet from the first electrode that is 1 foot from your property line and drive the second rod there. For the third electrode you run the Grounding Electrode Conductor (GEC) 16 feet in that other direction to a point 1 foot inside the property line. Drive the third rod there. The minimum size of the Grounding Electrode Conductor is #6 American Wire Gauge (AWG) if you protect it from physical damage by using Rigid Metallic or Rigid Non Metallic Conduit until it is 1&1/2 foot underground. The electrical code requires that the GEC be buried 1&1/2 foot deep but as long as it is deep enough to avoid being cut by lawn care and gardening equipment you'll be all right. If you have a wide side yard then the angle between the wires going to each ground rod should be no closer than 45 degrees. That will form an equilateral triangle that is 16 feet on each side so that all of the ground rods are at least twice their length apart. This is the same arrangement that you would use to ground an antenna tower. The manufacturers instructions would end up with exactly the same dimensions between the rods with each one coming directly away from a tower leg.

    By now you have figured out that the installation of a Grounding Electrode System; often called a Grounding Array in communications work; is going to take some work. This also offers you an opportunity to vastly improve the Grounding of your entire home. One form of Grounding Electrode is called a Ground Ring. That is a bare copper wire sized #2 AWG or larger buried not less than 30 inches and not less than 20 foot long encircling the entire building. Since you are not building this as the Electrical Service Grounding Electrode System you do not have to encircle the building. Test done at the National Institute of Standards and Technology (NIST) show that the actual length needed to make a significant improvement is 20 feet. Longer is in fact better but each additional foot provides less benefit than any of the first 20 feet did. To gain the significant improvement demonstrated in the NIST tests you need only dig the trench one more foot below the minimum depth of bury if the wire was just serving as the Grounding Electrode Conductor. You would also increase the size of the conductor from # 6 AWG to #2 AWG. In addition you will drive the Driven Rod Electrodes through the bottom of the trench thus placing them 2&1/2 feet deeper into the water table. If you do take on building a fully effective Grounding Electrode System make the job a little easier and buy 3 Harger 305 Ground Rod Clamps. They can be found for less than $15 on line and they save a lot of work.

    I have met a lot of hams who will install 100ds of ground radials for a counterpoise field beneath a vertical antenna and yet the same people will balk at installing a fully effective Grounding Electrode System to protect their home were the wires enter the building. Why is there never time to do it right but always time to do it again.

    --
    Tom W3TDH
     
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  8. KI7HSB

    KI7HSB Ham Member QRZ Page

    You're not ignorant, You're learning.

    Look at me... I went from tech to general to extra in just a couple months... because I could. I hold multiple engineering degrees, one of which is in electronics engineering. For me, the exam questions were easy, but I'm still building my first HF station and despite all my book learning and knowledge, I still have had to ask the same type of bone head questions about grounding and lighting protection and such as you are now.

    The FCC say that its a "license to operate", but for you, its really a license to learn.
     
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  9. N5YPJ

    N5YPJ QRZ Moderator QRZ Page

    Hi Dereck

    We recently replaced our gravel - tar roof with a sheet metal roof, galvanized unpainted metal panels screwed on to a plywood roof decking. Most of the antenna system is at least partially "over" the roof with the base of the 30 meter Delta loop entirely over it. Available space dictates the antenna placement.

    The baseball size hail storm that created the need for a new roof seems to have beat up the overhead electrical distribution system as since then my noise level has gotten quite high. 30 meters seems to be the worst band at 20 DB noise level but other bands range from 6 to 10 DB depending time of day. I plan to contact AEP Texas to ask them to check out what could be causing the problem.

    I'd like your opinion on grounding the metal roof to the bonded service - shack ground system and any recommendations on hardware if grounding is recommended.

    Thanks. Have a nice day.

    Richard
     
    Last edited: May 10, 2020
  10. KF5LJW

    KF5LJW Ham Member QRZ Page

    Hey Richard sorry for the delay in response, been gone a while. As for the metal roof, electrical codes are pretty clear on the subject. Metal objects likely to come into contact with electrical conductors shall be bonded. You have an antenna over it right? Maybe even your electrical service? Does not make any difference which one or both, they are likely to come into contact with the roof.

    As for method, if you have an overhead electrical service with a Weather Head Riser, bond it to the Riser Pipe with at least a 10 AWG. Otherwise run a bonding jumper from the AC Service Ground. If you have a radial electrode in a convenient location, drop straight down. You want to treat it as a Lightning Down Conductor. Just be aware, the roof will act as a Ground Plane and interact with your wire antenna.

    As for the noise coinciding with a hail storm sounds like cracked insulators arcing. You can help the POCO if you can get a old AM Transistor Radio or Walkman with AM. Something with earphones and a sledge hammer. Use the radio tuned to lower frequency off any active channels. You wanna listen to bacon frying. Drive or walk the line to find the source (pole). When you think you have located the pole or group of poles, thump them with the sledge hammer. If you hear a loud crash of noise, you found bad isolators. Tell the POCO what you did, they will know exactly what is happening as that is how they test isolators. They just use a different receiver.

    One last thing is to make sure your Service Neutral is in good repair and working order. I hesitate to tell you how, If you are not comfortable, hire a Sparky to do this. Open up your Main Service Panel, take a DMM and measure and monitor voltages on L1-L2, L1-N, L2-N. Pay close attention to the L1-N and L2-N. They should be roughly equal at all times. Do this with a lot of loads turned on in the house. Turn on all the 120 volt gizmos you got. If you see any imbalance in voltage, you got a Service Neutral issue. Call the POCO immediately, and you will hear the tires squeal as the Service Man pulls up before you get the phone hung up. If everything is normal L1-L2 = 230 to 250 volts, L1-N = L2-N = 115 to 125 volts. If L1-N = 160 and L2-N = 80 volts you are in extreme danger, and yeah extreme RFI.

    So first check your service out to eliminate the problem is yours. If you can go on battery, turn off your service also works to trouble shoot. Once you know you are good, go hunting.
     

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