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Grounding Rig In Basement

Discussion in 'General Technical Questions and Answers' started by KA7CTM, Feb 14, 2018.

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  1. KA7CTM

    KA7CTM Ham Member QRZ Page

    Getting into HF after a looooong time only doing 2m/70cm. Question is what should I ground out my HF rig to in a dug in basement? Copper water main pipe coming in from ground? Steel support pillar bolted to floor? Drive a stake just outside escape window and wire to that? Will the concrete floor provide a solid enough ground if I just lay a copper wire on the floor with a cinder block on it? Can I tap into the ground of an existing GFCI outlet or any other outlet? Thanks.
     
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    If your rig has a 3 prong AC cord then you don't need any additional safety ground at the rig itself.

    You should ground your antenna feed line where it enters the home and that ground should be bonded back to the AC service ground but that's not in the basement per se, it's where the coax enters your home.

    The need to ground each piece of equipment at its chassis is really a holdover from days when rigs had two prong AC cords and lacked an explicit AC safety ground. If you're running vintage gear like that then the best plan is to update their power cords for grounded three prong cords but if you don't want to do that you could run a shack ground bus for AC safety and make sure that's tied back to the home AC ground (not neutral) wiring.

    Basically there's three kinds of ground hams deal with:

    - AC safety ground: That's covered by modern home wiring and 3 prong outlets but could be handled with chassis grounding at the rigs if necessary.

    - RF Return: This is really part of the antenna system and if your antenna is well balanced like a dipole or doublet or vertical with a good field of radials then it's built into the antenna. If you run something like a random wire straight out of a shack tuner (not a great solution for a basement shack) then yes you'd want a good RF 'ground' very near the shack but that should be radials, ground screening, some form of counterpoise, etc. as it's really serving as a part of the radiating antenna and ground rods do not make for a good RF ground. Ground buses and other things in your shack are no substitute for a well planned antenna system that includes sufficient RF return and that should really happen outdoors, not in your basement.

    - Lightning surge protection ground: This is provided by grounding your coax shield and ideally using a lightning surge suppressor at the point where the coax enters your building. That ground point should either be the AC service ground itself or should be bonded back to the AC service ground with heavy gauge conductor. This isn't really about direct lightning strikes, if that happens all bets are off, it's about local or regional lightning induced surge events that momentarily cause either your antenna ground or the AC service ground to jump in potential. Grounding your coax shield where it enters the building and having that ground point bonded back to the AC service ground minimizes any ground circuit potential differences during such events which is a good thing.

    You'll still see magazine articles and web posts advocating a bus bar in your shack to tie all your equipment grounds together. There's really no reason for this in a home with modern wiring and rigs with modern AC cords. I suspect it's an attempt to cover the three bases described above and dates back to days when homes didn't run explicit ground wiring and antennas like random wires or Zepps fed straight out of a rig or tuner or were more common.
     
    KG7E likes this.
  3. N9AXL

    N9AXL Ham Member QRZ Page

    I run all vintage equipment (Drake mostly right now). I have everything connected by strap to a bus bar (copper pipe) which then goes through a passthrough to a four foot copper pipe in the ground outside the basement shack. All I can say is that this seems to work well enough. I keep hearing different things from "what you have is fine. Enjoy your radios" to "You are in immediate danger of burning down your house because you aren't running everything back to the house ground" In my case I think -- although I'm not sure -- it would be the large conduit on my deck where the electric enters the house -- that's where the direct TV people put their ground wire. I keep everything unplugged and the coax disconnected when I'm not operating. I guess that will have to be enough until someone who knows more tells me different.
     
  4. KA7CTM

    KA7CTM Ham Member QRZ Page

    Confused. I am running modern gear that is attached to a separate power supply. The power supply obviously plugs into the home. So, am I to understand that the power supply will supply the grounding even though there is a marked "GROUND" terminal on the back of the transceiver? I thought that the transceiver needs its own ground to disperse the RF energy from the antenna. I am just running a dipole at the moment..
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Correct, if you have modern three prong, thus grounded, AC outlets there is no reason to use the ground lug on the rig. It does not provide any additional safety ground and is not necessary.
    No, that's a common misunderstanding but there is no 'RF energy from the antenna to disperse' in a well balanced antenna system that includes your dipole. There may be some residual common mode on your feed line depending on installation specifics but even then the best place to add grounding is at the coax entry point to the home via NEC guidelines which also provides some safety for lightning induced ground potential surges.

    Your dipole, whether fed with coax or fed with balanced feed line and tuned in the shack as what's commonly called a doublet is a balanced RF antenna. Its design includes both a radiating element and an RF return. If the dipole is cut well (equal length in the halves) and installed well (up in the clear with the feed line running perpendicular to the antenna and away from electrical noise sources) your antenna won't have any extra energy to disperse.

    In real world installations there's often a bit of imbalance that presents itself as common mode currents on the feed line (the outer shield of coax fed antennas). A good current choke balun at the antenna feed point can minimize common mode currents which can lead to noise issues and or RFI in the shack issues. Grounding the coax shield where the coax enters the house with a ground rod bonded back to the AC service entry ground can further minimize common mode current issues in the shack as can a second common mode choke (aka line isolator) at the point where the coax enters the house.

    So if you skip the coax entry grounding and the choke balun/isolator and happen to have a somewhat unbalanced antenna then yes you could have some common mode and in that case it's possible that grounding the rig would improve receiver noise or other common mode issues. But that's really not the best way to handle those issues and is sort of a band aid to the actual problem but why you might read that some ham saw great improvement in things like RFI or receive noise after they grounded their rig. If it helps then the problem is elsewhere and there are better ways to deal with it.

    Best practices would be to:
    - Ensure the overall antenna system is well balanced as it should be in the case of a dipole, Yagi, Hexbeam, vertical or inverted-L with a good field of radials, etc.
    - Use a current balun at the antenna feed point (which does nothing if the antenna is well balanced but is cheap insurance against common mode issues)
    - Ground the coax shield and perhaps use a lightning arrestor where the coax enters the home with that ground bonded back to your AC service ground per NEC
    - Perhaps use another common mode choke (line isolator) at that same point which again won't really do anything if the antenna system is well balanced and not coupling energy either from the antenna itself (e.g. feed line runs parallel and not perpendicular to the antenna) or from local noise sources (e.g. feed line runs next to a CATV or DSL line and picks up broadband RFI that elevates your receiver noise floor)

    But really all of the above are about the antenna system itself. Grounding the rig's chassis is not the best place to deal with antenna system balance and common mode issues.
     
    KG7E and WD8T like this.
  6. W6UV

    W6UV Premium Subscriber QRZ Page

    No, it doesn't. If you have common mode current on the shield of your coax, you need a choke mounted (preferably) at the antenna feed point to force it into the antenna rather than onto the coax shield. You can buy a current balun and use that at the feed point of your dipole, or just coil some of the coax into a loop and tape or tie wrap it so it stays in place. This is all described in the ARRL Handbook and Antenna Book.
     
  7. WA3QGD

    WA3QGD Ham Member QRZ Page

    First,a bond is what your are doing with your coax or other antennae connection,it shall not be a current carrying conductor,bonding and grounding limits the level of a potential fault.If you have RF currents on your grounding system,you have an antennae problem.You are not building a commercial head end 24/7 communications system.You may need up to a #10 copper wire to cover the bonding needs of a 1500watt amateur station.Knowing what the Terms mean as to point of entry.Attachment point,Service point and others will lead to a clearer understanding.Now if your worried about lightning then it's an entirely different problem with it's own specific requirements.To meet minimum national electrical code requirements you are required to BOND to the electrical service grounding electrode SYSTEM,and then only to DISCHARGE when a potential difference exceeding the devices set level of clamping allows.If your carrying current on a grounding electrode system then you have a fault that needs to be eliminated and everything that is connected to that fault is at some potential above ground.You can Thank an engineer for making it so unclear.
     
  8. W5RKL

    W5RKL Ham Member QRZ Page

    I recommend reading Tom Rauch, W8JI, website on grounding.


    Click the following link.

    http://w8ji.com/ground_systems.htm

    When the page comes up, click the "House Ground Layout" link and study the drawings and write ups Tom has provided.


    73
    Mike W5RKL
    www.w5rkl.com
     
  9. WA9SVD

    WA9SVD Ham Member QRZ Page

    Whatever you do, the LAST thing you want is to ground INSIDE your building! A ground rod (8' or more, or maybe a couple, TIED to your electrical system ground is the best, and really only, way to go. You do NOT want to invite the lightning inside your house! Ands thaty INCLUDES the ground.
     
  10. K9STH

    K9STH Ham Member Volunteer Moderator QRZ Page

    Having been, before retiring, a telecommunications consultant with one of my "specialties" being lightning protection and grounding, I always do recommend having external, to the building, ground rods connected to the equipment in addition to the ground provided by the ground rod where the AC mains enter the building.

    Frankly, way too many of these electrical "grounds" are not that good. Sometimes, the electrical contractor does not follow "code" and puts in a much shorter than the required 8-foot ground rod. Sometimes, the contractor does not make that good a connection at either the entrance point or at the rod itself. Often, over time, corrosion builds up on the electrical entrance ground connections and that can cause problems.

    Of course, any added ground rods definitely need to be connected to the electrical entrance ground rods per NFPA NEC ("national electrical code") requirements. Also, the shield, of any coaxial cables, needs to be grounded as near the point of entry in the building as possible. In addition, when there is a tower, metal mast, etc., involved, then the coaxial cable shield needs to be grounded as near the top of that support and at the point where the cable leaves the support to go into the building.

    Frankly, the main usable function of the various lightning protection devices, placed on the coaxial cable, is to get the shield grounded. There are other ways, that are considerably cheaper, to achieve the same thing. The manufacturer of Heliax, as well as some of the other manufacturers of such cable, has available a kit to ground the shield of the cable. Although these are not that expensive, the amateur radio operator can do the same thing for well under $1.00 per cable using some braid, a hose clamp, and some cheap black plastic tape.

    Here is an example of how to do this:

    coax-grounding-1.jpg

    Another thing is that the better r.f. grounding rods are not that effective for lightning protection and the better grounding rods for lightning protection are often not that effective for r.f. grounding. However, to meet NFPA NEC requirements, as well as being the right thing to do, all ground rods need to be connected together and with the ground rod at the AC mains entrance. Of course, there are situations where doing such is a practical impossibility. But, whenever possible, this needs to be avoided.

    Also, for r.f. grounding, as short a connection as possible, between inside and outside, needs to be as short as possible. It is possible to have longer connections if the inductance of the conductor is at a relative minimum. For example, aluminum flashing, that is available in widths from like 4-inches to at least 30-inches, can be used up to the point where contact is made with the soil. Since aluminum corrodes badly when in contact with most soil types, one needs to keep the aluminum a few inches away from the soil and then transition from the aluminum to a large diameter copper wire going to the ground rod. Of course, provision to handle the dissimilar metals needs to be employed.

    For r.f. grounding, a series of 5-foot rods placed 12-feet apart is much better than a single rod 8-feet or 10-feet long. In fact, chemical ground rods, that are easy to make, work better than solid ground rods for r.f. grounding. However, such rods are usually not that good for lightning protection. As such, the usual 8-foot to 10-foot rods need to be employed for lightning protection as well as the shorter chemical rods for better r.f. grounding. Again, they all need to be connected together.

    Glen, K9STH
     

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