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Thread: Grounding in the shack help, opinions.

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    Premium Member rob916's Avatar
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    Default Grounding in the shack help, opinions.

    Just setting up my radio shack properly and would like to know some of your comments, experiences.
    I have been reading for weeks and am still none the wiser.
    Should multiple transmitters and receivers be grounded to the same ground point?
    Should PC's chassis be grounded to this point as well?
    Should this point be chained to your electrical safety earth?

    I am not asking about lightning ground (this seems pretty obvious, being the shortest, straightest path of least resistance) but is certainly open to discussion.

    It all looks like a big can of worms, too many different opinions to make sense of.
    Thanks for your input.
    What happens if I press alt + F4?



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    Senior Member Studio1's Avatar
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    I work in the broadcast industry and I build and wire out studios. On-air studios are quite demanding, when it comes to grounding and power supply.

    The trick with audio equipment and mains power is to have separate earths.

    You have a "technical earth" and a "mains earth".

    The idea is that your audio gear (shack gear in your case) ONLY connects to the technical earth.

    The rest of the stuff in your house including noisy electrical appliances such as fridges, freezers, air con units et al - all connect to the normal "mains earth".

    In your shack, create a technical earth by sinking a 2 metre earth stake into the ground outside the shack. Run a 6 mm earth conduit cable inside and tag it as such.
    If possible, connect this 6 mm˛ cable to a stud point somewhere so you can attach your feeders from the hotpoints to it.

    The hotpoints are wired "star" earth.

    Each hotpoint's earth connection goes back to the tech earth stud on its own cable.

    Don't "daisy chain" the earths from one hotpoint to the next - this will cause hum loops.

    If you wire your shack this way, you should have no noise issues at all. I have wired out dozens of studios this way and never had any noise or hum issues on-air. This is important in broadcasting as if there is any noise in the system it becomes very noticeable on-air.

    In reply to your specific questions:

    Don't connect your tech earth to the main house earth.
    Yes, you can connect your computers to the tech earth - if they are connected to any of your radio gear (ie data controlled radio where there is a cable between a radio and the computer).
    If the computers are not connected to the radios in any way, then run them from a hotpoint that is connected to the main earth. This will keep noise off the tech earth.

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    Premium Member rob916's Avatar
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    Very well explained Studio1.
    Thanks for your help.
    What happens if I press alt + F4?

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    Working in big end telecommunications the situation is much the same as Studio1 mentions.

    Earth systems follow a tree structure. Loops and daisy chains aren't acceptable, and most important that not only fault protection earths from power systems are seperate, but seperate technologies are on their own branches of their own trees.

    Like the tree, the grounding system is a lot like a root system of a tree, but for simplicity a single earth stake is enough. The in ground system can have loops, the purpose is to keep all points of the ground at the same potential.

    If your water supply is copper pipe, bonding to it is more than acceptable.
    Sinking your own earth stake or earth mat is also ok.

    The final touch which seems to defy logic is to bond the protective earth and the communications earth together so that they are at the same potential.
    This is often done with a purple colour cable.

    For a simple ham shack a bond to the cold water tap with a 16mm^2 cable into the shack to a small copper busbar. Then 6mm^2 cables run out to each radio that requires it.
    You may be able to find the power protective earth stake for the 240V in your house. Use a multimeter to measure the resistance between that earth point and the bond to the water tap. If it's more than a couple of ohms then a bonding cable might be required, and you'd be best to consult a sparky for that job.

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    Premium Member rob916's Avatar
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    The mains earth is at the other end of the house. All my water pipes are pvc.
    Can you have two mains earths? Another one close to my shack?
    What happens if I press alt + F4?

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    When the state railway installed a communications hut nearby, I noticed they put an earth stake in at each corner.
    The mast is a 40 foot concrete pole with 2 pair of directionaly opposed Yagis and a long gal vetical pipe on top I took for the lightning rod.
    I am guessing that there is a pair of tranceivers (one redundant) along with maybe a landline link in the hut along with all sorts of associated equipment.
    Mains power is available and possibly a battery backup for emergencies.
    The coax from the antennas is run inside the hollow concrete mast.
    I am not sure it the lightning strap is inside or outside the mast.

    In this instance, would they have connected appliances, depending how many there are and where they are located in the hut, each to a seperate corner 'Tech' earth?
    There is an electricty meter box mounted externaly and I am sure it has its own earth wire and stake.

    Re the PVC water pipes, I remember reading a warning regarding older houses with copper/Gal water pipes that had been repaired with PVC sections.
    In this article the stove/appliance had been earthed to the pipe near the kitchen tap end but because the pipe had been repaired with PVC, that meant it was now not connected to the earth at the meter end and could become 'Live' in the event of a fault.
    The wiring here was origonaly 2 single wires ruber insulated and cotton covered, coloured black and beige? in tin conduit with an external bare earth wire running across the ceiling to the meter box and then to the Gal water pipe.Broken in 5 places the electrician found.

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    Quote Originally Posted by rob916 View Post
    The mains earth is at the other end of the house. All my water pipes are pvc.
    Can you have two mains earths? Another one close to my shack?
    Even old houses they tend to have a protective earth stake that is then bonded to a water pipe close by.

    If you have two protective earth stakes it isn't neccisary to bond them together, but it can be a good idea. They should only be bonded stake to stake at ground level and nowhere else.

    The best way to consider your earth system is to think of the worst case scenario. That is that one earth stake fails and a piece of equipment goes faulty putting active potential on the chassis. Another piece of equipment is on the other earth. When the user connects the two together with say an RCA audio cable, the sparks fly. Or worse, the user puts his hand on the faulty chassis while hanging onto the earth of the cable. Bzzzzzzzt.

    Earthing is all about distributing zero volts as evenly and as far as possible.

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    Premium Member rob916's Avatar
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    All pvc pipes from the mains. No gal anywhere. My 240v safety earth is some small dodgy copper rod. I am going to put in some real stuff for the shack.

    I got a good spot for my earth stake, under the hot water service overflow, always wet, less resistance ( is this good or bad?).
    What happens if I press alt + F4?

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    Quote Originally Posted by rob916 View Post
    All pvc pipes from the mains. No gal anywhere. My 240v safety earth is some small dodgy copper rod. I am going to put in some real stuff for the shack.

    I got a good spot for my earth stake, under the hot water service overflow, always wet, less resistance ( is this good or bad?).
    Less resistance in any earthing/grounding system is always good..

    I have several earth stakes for my workshop/control room/studio... After a lightning strike in feb 2007, I'm not taking any chances..

    I also have plastic water piping (newer house), so the water pipes cant be used for earthing.. And I also remember the old 2 core wiring in the split metal conduit with the bare earth wire - gee that takes me back!

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    On some of the signalling equipment in NSW country areas (Circa 1960's), they used the 'Ground Return System' and it was a requirement for the station staff or a fettler to water the earth stake at regular intervals, or if it failed, just to pee on it for a quick fix.
    I had an inspector get up me about the dry ground around the stake untill I told him that the signal electrician advised it didnt have to be watered as there was a common wire earth used between the signal locations and this was progressively replacing the 'Ground Return System'.
    The stake was more for lightning protection now.A real problem with miles of aerial telephony lines.
    There was also some sort of a compound put around the stake to keep the moisture there, I wonder if it was that Gell you use on plants today?

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    You can improve the Earth by "star wiring" multiple earth rods together, ie, the shack earth cable runs down to a point, and then has multiple earth rods star wired (equidistant) from this point. Multiple rods will give a lower earth resistance.
    Common sense isn't !!!

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    A friend suggested an idea. An earth stake doesn't offer a great surface area to interface with the earth. Copper has much less RF resistance than stainless steel.... but copper corrodes and would need replacement occasionally.
    So the thought was to use an old salvaged stainless steel sink, attach your earth to it, bury it and use that for your earth.
    Now try explaining that to your neighbours... hehe.

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    I would be careful where you drive in these earth stakes . Some are quite long and you will find storm water and even sewer pipes are in range of these earth stakes .

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    When I worked in the HF communications industry some years ago, we used to supply plated tubular earth stakes. I don't remember what the plating was, but I suspect it was nickel.
    Soil conductivity (resistance) varies with moisture content and is very high in dry soil conditions.
    In dry weather, e.g. summer, we used to keep the earth damp to improve soil conductivity, by pouring water down the tubular earth stake every few days.

    These were essentially RF earth's rather than mains earths, but the same rationale applies.

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    This is a simplified example of an earthing system you might find in a telephone exchange.





    Remember "TREE" is the structure definition.

    At the heart of an exchange earthing system is one big Copper Earth Bar.
    This is THE EARTH - 0V absolute (not really but it is for this example).

    Below the Earth bar are the earth states. These are sunk at the perimeter of the building or compound. How deep they are sunk depends on the engineering design. Big high voltage switching yards they may be sunk 50ft deep. But for a communications building 6ft would be suitable for most situations.

    Each stake is bonded with an earth cable to the Main Earth bar.
    They may also be bonded to each other via the next closest stakes.

    From the main earth bar everything else is connected to this one point and ONLY this one point. This is ONLY communications equipment and communications power supplies.

    Lightening rods are not connected to this earthing system. I've not shown them because they are not part of this system.

    240V power (protective earth) is included because the building has 240V GPOs, lights and 240V powered comms equipment.
    But this earthing system is to protect people from the grid electricity, not to protect equipment from noise.

    Back to the comms earth. The main bar is the trunk of the tree. From here there are branch earth bars. One for each floor or equipment room of a building, and then one earth bar for each kind of equipment.

    An earth bar for IP equipment, an earth bar for ATM, for PSTN, for ISDN, ADSL. Never shall any of these earths touch each other and they will only meet at the main earth bar.

    The same shall be said for comms DC power supplies. Though one DC distribution system may supply different pieces of equipment, it's earth is still separate. The internal power supplies in the equipment are isolated with DC to DC converters. So the Power Earth is for DC fault currents while the communications earth is for electrical comms noise.

    Even equipment racks are isolated from each other. Their earthing system may also form a tree, or more a like a vine. Still there are no loops.

    The key thinking is; If a fault occurs that current has only one way back to earth.

    240VAC has a slight exception. The purple bonding wire between the 240V protective earth and the communications earth. Why is that there if it breaks the rules ?
    The reason is that If a 240VAC fault occurs and it fails onto the comms earth, then the fault current will find the lowest resistance path back to the phase neutral protective earth.
    Normally this would be down the comms earth tree and through the ground and back to the protective earthing system. However, if there is a lower resistance path, then the current will follow that path.
    This could be a worker holding onto a power drill in one hand and his other hand is supporting him against a router. The drill goes faulty onto the bit.
    The fault current can return to the protective earth via our worker's arms or if the path via the purple bond cable is a lower resistance, then most of the current will return via the bond and trip the breaker before our worker is toast.

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    I live in units with plastic plumbing pipes, so have earthed my Icom 7000 to the Earth pin of a power point.

    It got rid of some interference in my PC speakers whilst transmitting, especially at lower freqs.

    I suppose I could 'earth' my rig to the corrugated tin roof and light up the neighbour's hifi

    As the body corporate wouldn't appreciate an earth strap running on the outside wall, is there an alternative for unit dwellers?

    Thanks.

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    have earthed my Icom 7000 to the Earth pin of a power point.
    While it works, it is a dangerous thing to do.

    As the body corporate wouldn't appreciate an earth strap running on the outside wall, is there an alternative for unit dwellers?
    Body Corp... one of my favourite institutions of stupidity.
    You have to remember that the Body Corp is supposed to be there to make things better and easier for everybody. If they are making things harder, then they aren't doing their job and this is your signal to fvck with them.
    You'll have to assess their helpfulness yourself. If you find they are not helpful; Don't ask permission, it's easier just to demand forgiveness.
    Screwing them around costs them more money and time than it does for you to deny all involvement in your crimes.

    I'd look to the cold water tap first thing and try and confirm that it is (or isn't) Earth potential. Connect your earth cable to the water pipe in where the hot water system is.

    There is another option and that is to find the cable risers in the building for power and telephone and put your own earth cable in there. If you can get permission, fine. If not and you can get access to the risers. Do it anyway.
    There isn't a sparky on the planet that will rip out an official looking earth cable.

    A standard earth strap is actually a very low visible thing anyway.
    A galvanised metal strip down the side of the building or even a bare wire fixed to the wall down to an earth stake.

    Low resistance and low visibility is the key.

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    My friend got an old car radiator and cut down his HF noise .

    Bury the radiator.

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