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Feedline and grounding questions

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by NY8I, Sep 15, 2019.

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  1. NY8I

    NY8I Ham Member QRZ Page

    Hi all,
    I am in the process of setting up some external antennas and want to check a couple of things. I'm going to be setting up multi-band dipole for HF and a Comet GP-3 for UHF/VHF. SGC remote antenna tuner for the dipole.

    Coax from both antennas will run to a basement utility room window through a plexiglass bulkhead I've made. I'm having an electrical contractor install an external ground rod and run additional #6 wire to the utility ground. I've explained what I'm trying to accomplish to the contractor. I have the following questions:

    a. The house (70's construction) is built on a slope and as far as I can tell the utility ground where the service enters the house is not visible. The contractor showed me the ground wire that connects to the incoming water main (all well underground for many feet), to which he is planning to bond the additional ground rod which is about 30 feet away. Is this common for the utility ground to basically be the water main? And, would that additional wire be OK to run through the house or does it have to run outside?

    b. I am going to use a metal entrance panel box with a copper ground sheet to which the new rod will be connected. The box will have lightning suppressors in between the incoming coax, and the outgoing coax, mounted on the grounding sheet - so all coax shields will be tied and grounded at one point. Does it matter if the box is installed outside the basement window or inside ~4 feet of additional distance from the ground rod? The ground wire will need to also come into the house in that case, through the bulkhead.

    c. Finally, I will use a copper busbar to bond my radio, PS and other equipment grounds together and run a ground wire to the ground rod (which is bonded to utility ground).

    Any advice/thoughts would be really appreciated!

    Thanks

    NY8I
     
  2. N5AF

    N5AF Premium Subscriber QRZ Page

    You are on the right track, but a couple of observations.

    1. Do NOT run the bonding between the new installed rod and the mains ground rod inside the house. Keep it outside and buried. Be sure your electrical contractor uses heavy gauge solid copper. I'd recommend #4 AWG solid copper, but I'm prone to overkill when it comes to grounding. (My home took a direct strike 35 years ago - it changes your perspective..)

    2. I would not put my coaxial grounding panel inside. In the event of a strike, you want the energy being shunted to ground outside, not coming inside then going back out. ;)

    I never lived in a location where it was common to bond to the water lines for grounding, so I can't speak to that part of your question. I personally have not seen that configuration in Florida or Texas, at least in residential construction built in the last 30-40 years.

    My coaxial panel right is outside the window to the shack. I have a copper bus bar under the desk. Radios and gear are connected to copper bar, and a single wire runs out my window panel back to the coaxial suppressor panel. The coaxial panel is connected to the mains ground via 2" copper strap. Everything here is connected back to the mains ground which goes down 24-feet. (Very soft soil at my QTH) I have six (16-foot long, two per tower leg) additional rods some distance out from my tower foundation in a radial pattern, all of which are tied back to the mains ground via single heavy conductor.

    I'm fortunate my mains entrance & ground is within 10-feet of my operating position. Keeps the wire runs very short. Good for my 240V feed too! I've linked some pictures below. The mains ground rod is about a foot to the right of the underground conduit coming up to the meter can.

    Overall view: https://i.imgur.com/aNCRdNI.jpg

    Window panel during construction phase - testing window fit: https://i.imgur.com/XS9Pfu5.jpg

    Completed window feed through 4-SO-239, 2 N-female, 4 F-female and two studs with wingnuts. Outdoor facing F, N and SO239's all have caps on them when not in use: https://i.imgur.com/VZjJBhA.jpg

    I recommend reading the first three sticky threads in this forum on grounding do's and don'ts by KF5LJW. He sums it up nicely in his first post: https://forums.qrz.com/index.php?threads/grounding-dos-donts-why-part-1.335582/

    Good luck!
     
    NE1U, AJ5J and WA7ARK like this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I have seen the "water pipe ground" as the main utility ground for a service panel, plenty of times. Homes from the 50s and 60s mostly; if the water pipe is an outdoor connection and goes directly underground, all metal (copper or galvanized) without interruption, it can make a fine ground.

    Earth isn't a good conductor anyway, but it's what we have and it's big and can dissipate a lot of energy...because it's big.:)

    I'd also avoid bringing in anything from outside to inside unless it's grounded outside. Not sure an "entrance panel box" is even needed; if you use a sheet of copper, brass, aluminum or galvanized steel to replace the window pane instead of plexiglas, that new "metal pane" can be your grounded entrance panel, without adding another one. But no harm in using a separate entrance panel box -- just adds "another thing" to the system, and probably some cost.

    Where cost is not much of an object, like in many commercial BC-telecom-industrial applications (where thousands of $$ may be spent on grounding systems), they do all sorts of stuff that most hams wouldn't do -- and those all work, but can be expensive.

    At my company, we had a big EMC test lab for many years and the "ground" for the lab was a 3" copper rod going 10' into the ground, right through the cement slab of the building. Making the "hole" for that probably cost a few $K, just to prep it. I remember jackhammers making a lot of noise.:p Then, everything in the lab from the ground of the anechoic chamber to all the test benches was all bonded to that using about 3" wide solid copper "foil" that was very thick and had to be cut on a pneumatic shear because you sure couldn't cut it with scissors or tin snips. None of that was for "safety," so bonding to the utility ground wasn't the issue -- it was to keep everything as close to "RF ground" as possible.

    Hams don't need to do that unless they have very deep pockets and feel like wasting money.:)
     
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  4. K0UO

    K0UO Platinum Subscriber Platinum Subscriber QRZ Page

    Screenshot_20190915-173434_Chrome.jpg Look on the Antenna forum, the first three post.
    Grounds: Has been hashed over hundreds of times, there's excellent information and comments about all your grounding needs there, so just do some reading.
     
  5. AI3V

    AI3V Ham Member QRZ Page

    You must not have very many smart people working there if you paid many thousands of dollars to drill a 3" hole in concrete:

    https://www.unitedrentals.com/marke...rete-masonry/core-drills/diamond-core-bit-3#/

    https://www.unitedrentals.com/marketplace/equipment/concrete-masonry/core-drills#/

    And you can cut 3" x 1/4" copper busbar with one of these, about 2 minutes a cut:

    [​IMG]

    Special pneumatic shears steve? Are you positive?

    Rege
     
    K0UO likes this.
  6. WB2JIX

    WB2JIX Ham Member QRZ Page

    I can see where this is going ....................................................
     
  7. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    A cold water pipe is no longer a preferred grounding conductor for AC mains. There is now the fact that PVC pipe has replaced metal pipe for most construction these days.

    In fact, unless the metal pipe joints were "wiped", which has not been common since before World War II, a cold water pipe often was not a good conductor. This is because the pipe joint compound, which was used to prevent leaks, in the connectors between pipe joints, elbows, etc., is a very good electrical insulator and there is often not a continuous electrical connection in the metal piping. Also, a lot of pipe has a fairly thick painted exterior which also insulates the pipe from contact with the earth. Galvanized pipe does come in contact with the earth but the pipe joint compound still is a problem. Soldered copper pipe does present a good conductor but copper pipe is not, generally, used for buried water lines.

    All conductors between ground rods, etc., must be kept external to the residence. To meet NFPA NEC (National Electrical Code), coaxial cable shields, from antennas, are to be grounded at the point where they enter the building. If equipment is to be grounded (which I do recommend), those connections should come to a single point inside the building and then a single conductor, as short as possible, then go outside to a ground rod as close to the building as possible.

    LJW and I differ, in some areas, about what we recommend for grounding. Neither one of us is wrong! We just have different approaches to achieving an excellent grounding system. For over 30-years, I have been a telecommunications consultant and 2 of my specialties are lightning protection and grounding. My recommendations have been implemented by, among others, several television transmitter manufacturers and the United States Naval War College.

    Glen, K9STH
     
  8. WR2E

    WR2E Ham Member QRZ Page

    Highly unlikely STH.

    The NPT threading that is used on water piping is a tapered thread. (NPT)

    Joint compound is used as LUBRICATION to allow tightening them properly, NOT a 'sealant'.

    When properly tightened, there is ALWAYS going to be full METAL TO METAL contact because of the way the threads are designed.

    The threads are designed such that there is an interference fit in the tapered threading.

    The interfering threads actually deform to create the seal when they are in contact with each other and the joint is properly tightened.

    This deformation forms the leak tight joint, and closes the 'spiral leak path' that exists, NOT the joint compound.

    I challenge you to show us a documented case where a properly installed water pipe system won't have full electrical conductivity across a threaded joint.

    I'm sure there are other reasons for not using water piping for ground these days, but joint compound insulating the two parts is definitely NOT one of them.
     
    WQ4G likes this.
  9. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    2E:

    The pipe threads are supposed to make metal to metal contact. However, in the past, I have seen a fair number of cases where the resistance across the pipe joints, when actually measured, has been anywhere from several hundred ohms to almost infinity.

    I have been informed that this was due to the pipe joint compound being / becoming an insulator.

    As for being a sealer to prevent leaks:

    https://www.doityourself.com/stry/pipe-joint-compound-vs-pipe-thread-sealant

    https://www.pvcfittingsonline.com/resource-center/pipe-thread-sealant-vs-pipe-joint-compound/

    https://www.oatey.com/ASSETS/DOCUMENTS/ITEMS/EN/Submittal_Hercules_TFEPipeJointTape.pdf

    The last one references electrical insulation.

    My mother's father, and her eldest brother, were plumbers and, in elementary school and junior high school, when they needed a "gofer", I was elected. It was not that long before I was cutting pipe, threading pipe, joining pipe, etc. In the 1950s, the pipe joint compound was more like putty rather than the liquids used today (or TFE tape). When the coupling was attached properly, the joint compound "oozed" out and was then wiped off to form a smooth seal between the end of the coupling and the pipe itself.

    Disassembling old pipe often showed dried joint compound throughout the surface between the pipe threads and the coupling. Although I had no reason to check the electrical conductivity, I am pretty sure that it was not all that good. Sometimes the pipe threads were pretty clean and sometimes the joint compound was caked all over the surface.

    It is primarily older houses / buildings where cold water pipes were / are used for grounding the AC mains. I do suspect that the majority of those pipes had the older type of joint compound used. Since plumbers were not interested in the electrical conductivity of the pipe, that feature was never checked. Therefore, it is a "hit and miss" if there was a good electrical contact made. Probably, most of the connections did have a good contact. However, there are still going to be a number of connections that do not have all that good electrical contact.

    Glen, K9STH



     
  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    Plain and simple:
    If your plumbing is used as your ground, please install a ground rod.

    Ed
     
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