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Single Point Grounding 4 Dummies

Discussion in 'General Technical Questions and Answers' started by KF5LJW, May 18, 2020.

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  1. KF5LJW

    KF5LJW Ham Member QRZ Page

    Due to overwhelming response, questions, phone calls, and thirst for more information, I decided to make a follow up. While talking on the phone with many of you, I was no table to cover some topics and connect all the dots.

    Bonding and Grounding can be a very confusing subject full of conflicting information, magic, and myths. As a result, leads many to misunderstand and come to the wrong conclusions. Many ideas when put to the test of Ohm’s, Series, and Parallel Circuit Laws fail to hold up. Ground becomes a meaningless mystery resulting in not knowing one Ground System from another, what it does, and doesn’t do. You are left with everything becomes Ground. Just one rats nest of jumbled up thoughts. Fortunately, it need not be complicated, in fact is straight forward and easy to understand.

    Single Point Grounding has been around a long time. Originally developed in the 70’s by Bell Labs during the digital switching era. Since that time has migrated from telecom switching to all facets of telecommunications and electrical codes. Default choice used in the wireless, cellular, commercial carriers, LMR, and Broadcast technologies. There are many grounding and bonding standards out there like Motorola R56, ANSI T-333. And ARRL Grounding and Bonding for Amateurs. All are based on Single Point Ground methods. They use it because it works well with a long-documented proven history. It is easy to implement anywhere, even on top of a high-rise building. SPG meets three primary objectives;

    1. Meets or exceeds all electrical codes making it as safe as possible.

    2. Maximum lightning and utility high voltage protection architecture offered.

    3. Minimizes RFI/EMF issues.

    The confusion starts by not identifying what Ground System is being considered, what it does, and most importantly what it does not do. There can many Ground Systems in any given facility. Examples are: Earth Ground (ground electrodes), Lightning Protection System (LPS), AC Equipment Ground Conductor (EGC), DC Equipment Ground Conductors (DCEG), Station Ground, Chassis Ground, Signal Ground and so on. Ground Systems are not interchangeable with each other, or capable of doing what the other Ground System can do. All Ground Systems are dedicated circuits, isolated from each other, and originate at a Single Common Point called GROUND. Doing so means each Ground System is at the same voltage potential with no voltage differences between any two Ground Systems. Apply Ohm’s Law to test; 0 current through essentially 0 Ohms between the two far ends of any two Ground Systems. Voltage = 0 Amps x Y Ohms = 0 Voltage. Free of noise, current, voltage, and is safe.

    We hams get off fairly easy. Two of the three Ground Systems you need are already built for you. At most a ham operator will only require 3 Ground Systems consisting of Earth Ground, AC Equipment Ground, and a possibly Station Ground MIGHT be needed for some. It is important to understand what each of the three Ground Systems does and especially what it cannot do.

    Let’s start from the ground up with Earth Ground. This Ground System trips up a lot of people, leading them to draw the wrong conclusions from the start. From there, all other assumptions and conclusions are wrong based on a false assumptions to start with. It leads to conclusions that that will not stand up to any test of Ohm’s, Series, or Parallel Circuit laws. Examples;

    a. Earth Ground, is a magic conductor with lower impedance than your coax shield.

    b. Makes fuses and breakers operate.

    c. Where you dump noise.

    d. More Earth Grounds are better than one.

    All the above is false. To be true would require dirt to be as good of a conductor as copper. All easily disproved with either Ohm’s Law and/or basic circuit analysis using Series and Parallel Circuit Laws. That is why all electrical codes and best practices do not permit dirt to be used as a conductor, not even RF. Dirt is not capable of doing any of those things at low voltages because the resistance is way too high, even the mythical 5-Ohm ground is way too high to be of any use as a conductor. If you bust the 5-Ohm myth, the rest of the Dominoes fall and the logic falls apart. Let’s Bust it now so we can move on past it.

    A 5-Ohm Ground Resistance reading is a Power Frequency measurement made at 140 to 190 Hz. Those frequencies are close enough to DC that we can ignore the impedance and say the DC Resistance is 5-Ohm’s. Has nothing to do with any RF frequencies or lightning. Ground Electrode Systems (GES) are made from mostly Ground Rods which are Inductively coupled to Earth. Great for DC and low power frequencies. Lower in frequency you go below 60 Hz, the lower the total Impedance is until you bottom out at 5-Ohms DC resistance. You know what happens as the Frequency goes up right? Impedance goes off the scale up toward infinity.

    If that was not enough, compound the fact there is no single wire conductor or cable that will conduct any RF frequency without a lot of Impedance getting in the way. DC and 60 Hz, not problem. Example say we construct a Station Ground System with a 10-foot length of 750 MCM Fine Stranded DLO Cable. Has massive surface area, Constructed of fine stranded copper wire with a cross-sectional area the size of your wrist. One end to a dirt 5-ohm ground, and the other end inside the shack bonded to Station Ground BAR. It is a Single Wire Ground Cable. Not ran or associated with any associated circuit conductors cancelling out inductance. As such, we look up the impedance at various frequencies in IEEE-1100 for a 10-foot section of 750 MCM. First stop is 1 Mhz and the 750 cable has roughly 1000-ohms of impedance in series with our 5-ohms. Incidentally about the same Impedance with 6 AWG. As we move up in Frequency the Impedance raises proportionately with frequency. We keep going up and magic happens. At around 24 Mhz we get a dip in impedance as we hit resonance and it goes down to 30 or 40 Ohms in series with 5 ohms. Completely worthless as a circuit conductor. A circuit conductor like a coax shield, battery return, or neutral is on the order of single digit milli-Ohms, like .009 Ohms in parallel with what? Did you say 10’s, 100’s, or 1000’s of Ohm’s maybe even open circuit. Won’t work, BUSTED.

    That 5-Ohm Ground comes from the Civil War and early days of telephone party lines. They used dirt as a return circuit conductor to make the clacker clack and your phone ring. Both used earth as a circuit conductor from DC (Telegraph) up to 50 Hz (telephone ringer frequencies), where it was possible to use earth as a circuit. Those days are long gone. No more telegraph or party lines. Ring voltage today is only applied Tip to Ring.

    What Earth Ground is for. Nothing more, nothing less.

    1. Primary and most important function is providing a planned Fault Path to earth for utility high voltage and lightning faults. Must be capable of safely (thermally) sinking those fault currents to earth, returning them to their source (Utility or Earth). It prevents outside faults from entering and seeking EARTH inside. This is not limited to the Electric Utility. Any source or services like CATV, Telephone. ISP, and Radio Antenna Coax can all carry lightning utility faults. All those services are capable of carrying lethal surges if they come in contact with the Utility and Lightning upstream, or a direct strike. It protects you, your equipment, and your home from the outside World by not allowing outside faults to enter and exit via another Earth Ground. Assuming you do not provide another path to Earth through your home.

    2. Primary interest to hams is; Earth Ground provides a 0-VOLT Reference Point for all Electrical, Electronic, and Ground Systems. Two important points need to be noted. From a safety and code point of view, provides 0-Volt Touch Potential difference on raceways, equipment frames, equipment chassis, and exposed metal surfaces. So, when you touch something, it does not shock you under normal operating conditions. From a performance point of view, provides 0-Volt Reference between all electrical systems like AC, DC, Ground Systems, and Input/output signal ports. It is the Single Point from which ALL VOLTAGES ARE REFERENCED to. It is a Singular Point, not up or downstream electrically. If you think ham radio systems are sensitive to noise, you have not seen nothing yet. Try data centers with 10’s of thousands of I/O ports interconnected to multiple electrical, electronic and all ground systems. They have to be using the exact same 0-Volt reference point. Otherwise you will just run a lot of errors, caused by common mode currents flowing between systems. It is very important to understand 0-Volt Refence Point. Otherwise you can end up putting yourself between two Earth Grounds caught hopelessly lost inside a Ground Loop.

    3. Planned discharge path for static electricity. The one and only current you are permitted to dump into dirt.

    4. Lastly shorts out capacitance coupling between circuit conductors inside a facility. Eventually damaging the wire insulation. Your home wiring is way to small (lengths of circuits) to worry about this. Thus, a moot point.

    5. Keeps the Boogie Man and Gremlins outside where they belong. Its magic in that way.

    Earth Ground only does two things you as a ham should be concerned with. 1 and 2 above. It is not capable of doing anything else. This Ground System is where you need to invest you hard earned dollars as this is where you get the most bang for your buck. Improving what the Electrician did initially. Expand it away from your house using Radials to direct lightning and utility faults away from you.

    Where is Earth Ground? Outside obviously, and it is a System. NEC calls Earth Ground a Ground Electrode System aka GES as defined in NEC 250.50 and 250.52. It consists of Rods, Pipes, Metal Plates, Building Steel. Ground Rings. Concrete Encased Electrodes, Underground Metal Storage Tanks. Well Casings, Cold Water Pipe, Radials, and Bonding Jumpers beneath the surface. All Electrodes available must be used and bonded together to form a common GES per NEC 250.54. If none are available, then you must provide at least two Ground Electrodes made from any of the above listed. Once constructed, you connect or interface to the GES at one point only via the Ground Electrode Conductor aka GEC. The conductor rising up out of the ground going to your AC Service Disconnect Device, your meter can.

    That brings us to the two Equipment Ground Systems used in the shack. One you must have, and already have is the AC Equipment Ground. The other if needed, is a Station Ground. Both perform similar functions, and are not interchangeable with each other. They are separate, isolated, and dedicated Ground Systems. They both Originate from a Singular Point called Ground. Both do roughly the same job

    1. Provides a planned dedicated fault path back to the source of power in the event of an accidental contact between line and chassis or battery positive to chassis. It allows your over current protection device (Fuses and Breaker) to operate quickly and efficiently to clear the fault.

    2. Extends 0-Volt Reference from Earth to the equipment frames/chassis, and provides your 0-Volt reference to I/O ports. No touch potential on equipment frames to shock you if touched, and a nice quite 0-volt reference for I/O ports.

    Short story is all Equipment Grounds, both AC Equipment Ground Conductors and Station Ground Conductors are for safety and 0-Volt reference only. Nothing more, nothing less. If you were to force or allow currents to flow on your Equipment Grounds, you completely defeat their purpose, turning them into Circuit Conductors. If you force or allow any kind of current, be it DC or AC (RF = AC) will induce a voltage drop along the length of the conductor. Ohms law confirms this: Voltage = Current x Resistance. If you have current flowing in Equipment Grounds means all your equipment chassis are at different voltage potentials with respect to O-Volt Reference located at the other end of your Equipment Grounds. Your equipment frames and chassis will not be at 0-volts.

    Let’s go into a little more detail on Equipment Grounds starting with AC Equipment Grounds. For many of you is all you need, and already done for you. You can and should improve this circuit. Money well spent Run at least one Dedicated 20-Amp over-sized circuit to the shack with a Quad Receptacle using 10-3 NMB cable. This has more to do with controlling Voltage Loss using over-sized circuit conductors.

    From a Ground Performance point of view, eliminates possible common mode currents being injected into the AC Equipment Ground Conductor (EGC) either upstream or downstream from you. Your wall outlets are not dedicated circuits. Typically, there are 3 or more daisy-chained together called General Purpose Outlets. That can allow say your AV system on the same circuit in the next room to dump noise currents into the EGC. A dedicated Branch Circuit eliminates that possibility and one less thing to worry about and go wrong like ejecting Grandma from her power lift chair when you key up.

    The AC Equipment Ground is already a true Single Point Ground as required by electrical codes used in all facilities. Work with it, not against it. It was designed to operate as efficiently and effectively as possible. It is fine-tuned machine tuned exactly to 60-Hz or any power frequency used. Does not require or need Earth Ground to operate a fuse of breaker.

    This is accomplished by using a Transmission Line consisting of 3 tightly coupled conductors called Line, Neutral, and EGC . Those three conductors are closely spaced tightly together which results in magnetically coupling the three conductors together just like a Coax or Twin Lead transmission line. Under normal operating conditions current only flows in Line and Neutral circuit conductors. The current, be it DC or AC (RF = AC) in each conductor is 180 degrees out of phase with each other. This interaction cancels out Mutual Inductance between the two conductors, eliminating Inductance leaving you with mostly the pure DC Resistance of the conductors. The Impedance is canceled out making it possible to transfer power at any frequency from DC to light. Single wire circuits cannot do that. It is impossible. Ohm’s Law confirms. Voltage / Resistance = Current. Code requires all Branch Circuits to be closely coupled for this very reason. Not magic, basic fundamentals.

    So, if all you have is plug n cord connected equipment connected to AC power, your done. If this is you, all you really need to do is run a dedicated AC circuit to the shack, and consider improving your Earth Ground System. Install a NEC defined 250.94 Inter-System Bonding Bar on the GEC coming up out of dirt going to your AC Meter Can to facilitate bonding your coax shields and ADU’s before going into your house. Be sure all other services are bonded like CATV, SATV, ISP, and Telco. Stick a fork in it, your done.

    Now someone going to come along and say something like, I have not considered RF currents are being induced in Ground Systems by a high-powered transmitter. That fact has not escaped me, or other Power Quality and RF Engineers. It is a symptom of a compromised antenna system we ham radio operators are famous for. Your antenna is either too close to the house (within 2 wavelengths of less), and/or not high enough above dirt. You made a transformer using brute force RF magnetically coupling into your Ground Systems. Your active antenna elements are too close. (house with wires). Or not high enough above dirt making a Cloud Warmer and Earth Work Spa heating up dirt being less than ¼ wavelength above dirt. You shot yourself in the foot and now suffering ground losses. You got what you ask for. Dang physics does it again. However, that someone special is right about 1% of the time, and he has got me.

    Your Equipment Grounds is a long wire, generally 20 to 50 feet one-way length, with 8 feet of insulation stripped off one end, bare wire end stuck in the mud, running up out of the mud a few feet, turns horizontal and runs 10 to 40 feet and dead ends into an open circuit (your equipment chassis) going nowhere. A long wire stuck in mud standing up above dirt. Sounds familiar huh? You have an antenna where at a few predictable frequencies will resonate and allow RF current to flow. That Frequency is predictable and likely will not fall in an operational frequency. So, someone is right about 1% of the time. Put your antenna too close, within 2 wave lengths, and RF is going to magnetically couple into your equipment ground at a few resonate frequencies with the transformer you worked on so hard to make. Even then is a very poor conductor, otherwise open circuit at all other frequencies. Very easy to work with and stop the current.

    Meanwhile Power Quality and RF Engineers have known about this for decades, and know exactly how to resolve it. They too run into situations where it is not possible to keep antennas far enough away from the equipment shelter. They know how to resolve the issue quickly and effectively ridding themselves of Ground Losses and chasing ghost.

    A Power Quality Engineer would use something you cannot see, inexpensive, and extremely effective at removing Common Mode Current, an AC Line Common Mode Filter. Example, install a common mode AC Line Filter inside the DC Power Supply or Linear just after the On/Off switch to Block or Choke off RF currents from flowing on the EGC. They even make them with MOV’s to add Surge Protection.

    An RF Engineer on the other hand is a crude bull in a china shop. He would wind the AC Power Cord around an ugly large Snap-On core. Ugly but very effective. Nope they would never try to improve Earth Ground because they know that will not work, they tried it once and failed. Nope they choke the snot out of Ground Systems to block RF currents. Essentially a very very Low Pass Filter that allows the EGC to do its job with power frequencies unimpeded, and essentially an Open Circuit to 1 Mhz and higher frequencies. No more RF current on ground conductors

    Moving on to Station Ground. More myths about this than all the other Ground Systems combined, and can get hams into trouble. Somehow it escapes all the laws of physics. Once you bust the 5-Ohm myth coupled with Single Wire Ground issues with series Impedance, the rest of the myths fall. Many will have a hard time accepting the Station Ground only functions are:

    1. Provides a planned fault path between AC 120 volt systems, DC 12 volt systems, and Auxiliary Equipment.

    2. 0-Volt Touch Potential Reference for Auxiliary Equipment like an Antenna Tuner.

    Ever wonder what those Ground Terminal Studs on the back of your radio equipment is used for? That is where a Station Ground comes in. Not every piece of equipment requires the Ground Stud to be terminated. This is one case, if it is not required, don’t do it because you will corrupt your Ground System. How do you know what equipment needs a bonding jumper to the Station Ground Bar?

    Real simple, if the equipment in question does not have an AC Power Cord, it is already properly grounded and DO NOT connect to Station Ground. It is for auxiliary passive equipment like; Antenna Tuner, SWR Bridges, and Coax Switches. All those pieces of electrical equipment are passive with exposed metal surfaces. They just have input and output ports. All electrical codes and practices require anything with metal that might come in contact with sources of electrical power like DC, AC, and RF, shall be bonded to Ground in the event there is a fault, and provide 0-Volt Touch Potential. Ever get a tingle when you touch your Antenna Tuner when the mic is keyed up? That tells you have a problem with Grounding. Coax Shields are not a Ground, they are grounded circuit conductors carrying normal operating current just like the neutral in an AC branch circuit or negative battery return in a DC feeder circuit. The Aux equipment is required to have a Safety Ground hard wired. No matter what the coaxes are doing, it will always have a solid safety ground. You can read up on it in ARRL Grounding and Bonding for Amateurs.

    What about your radio. Maybe, maybe not. Depends how and what is supplying power. Here is the bottom line. If it is a 12-volt radio, using a DC Power Supply, the answer depends if you left the bonding jumper inside the DC power bonding Negative to chassis or not. You should remove the jumper. Your radio will be Floating and require a bond to the Station Ground.

    Make no doubt about it, a Station Ground is a poor ground. Being a Single Wire Ground makes it unusable for anything except power frequencies from DC to 60 Hz. Even at 60 Hz is impeded not being coupled with an associated circuit conductor. Unlike the finely tuned high performance of an AC EGC being part of a Transmission Line to cancel out Inductance, the impedance on a Single Wire Ground is just way too high to be used for anything else other than power frequencies. Ever been led to believe a Station Ground is RF Ground?

    Even if you could make Ground impedance say .001 Ohm’s, last thing you would want to do is bleed off current from a coax shield and force it to flow on ground systems and dirt. Talk about common mode noise, you just generated it on purpose. You do the exact opposite, choke the snot out of it putting it back on the coax shield where it belongs.

    OK to construct a Station Ground is pretty straight forward with a few options to fit your application. This is one ground you want to oversize. Has nothing to do with AC or RF, and everything to do with DC resistance in the event there is a cross-system fault between AC and DC Systems. Use a 6 AWG, stranded copper, green insulation, for less than 40-feet, 4 AWG for greater than 40 feet. One end goes to NEC 250.94 IBT at the AC Service, and the other inside the shack. Inside the shack you have a few options. I prefer a copper buss bar drilled out for two-hole compression terminals, and land the conductor right in the middle of the buss bar. Never use the end points.

    Where I believe the RF Ground myth comes from is another option, a steel table to use as a Ground Plane to facilitate physically mounting Auxiliary Equipment directly on the table so there are no wire grounds between mounted equipment. Extremely low impedance between each device mounted to the Ground Plane, but to earth, other than DC and 60 Hz is unusable.

    Warning here, do not make incidental contact with any ground system especially EARTH GROUND. In radio sites, we use equipment racks bolted to the concrete floor. The concrete floor is part of Earth Ground system. We place 1/4 -inch isolation pads under the racks, and isolation bushings on the floor anchor bolts to electrically isolate the equipment racks. You get the idea, nothing complicated about it.

    Like the AC EGC, your Station Ground Conductor can resonate, and you fix it the same way, Choke it. You can even get ahead of it now by using a Choke. Wrap the Station Ground Cable around a large Snap-On like an RF Engineer would wrap the AC power cord before you terminate to a buss. That will block RF and allow Power Frequencies to flow in the event of a fault. Otherwise no current flows during normal operation and you have 0-voltage and current free Antenna Tuner you can touch when the mic is keyed up and not open/close the garage door.

    So where is GROUND? You know the Ground Systems now, what they do, and what they cannot do. But where exactly is Ground? It can be anywhere the designer wants it to be. An “X” on a wall where a Buss Bar is installed. On top of a sky scraper, a basement, or a ham sandwich on your dining room table. Wherever Ground is determined to be is a singular point in space, it does not move, it begins where it ends and goes nowhere else except straight to EARTH. It is the Point we declare 0-Voltage Reference, where all voltage measurements are referenced too.

    Hams get off here easy again because scientist, engineers, and electricians have already made the decision for you. How easy is that? Your home is configured as a Single Point Grounded System where one of the Circuit Conductors is referenced to Earth. Makes over current protection easy to implement so you only have to use fuses and breakers on the ungrounded Circuit Conductor like AC Line and DC Positive. Ground is not the cable disappearing into dirt. GROUND is the point where the GEC is bonded together to the AC Service Neutral Conductor inside your Meter Can.

    Obviously, you cannot access that point directly, but we do have what is called a Ground Window, an imaginary window within a 3-feet radius of that spot to effectively be the same spot electrically. Big ole Ground Bars telecom use make it huge and convenient. In other words, your NEC 250.94 IBT is bonded to the GEC between the AC Meter Can and dirt as close to the meter can as possible. All cables entering are bonded, and have to pass through the Ground Window before entering. From that point, never touches any Ground System again. Beyond that point is an Open Circuit. No outside currents can enter because there is no path to take with a single point connection. Work with it and life is simple, it was designed that way.

    Very simple, extremely effective, and easy to implement. Just needs to be thought and laid out before you get started making rats nest with no rhyme or reason.
     
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  2. KQ0J

    KQ0J XML Subscriber QRZ Page

    Would you mind if I sent this to the members of our radio club via email ? With your authorship of course...
     
  3. KF5LJW

    KF5LJW Ham Member QRZ Page

    Thank you for asking. Check your email.
     
  4. W9WQA

    W9WQA Ham Member QRZ Page

    W. O. W.
     
  5. W6KCS

    W6KCS Ham Member QRZ Page

    This is excellent, Dereck. I know it's past the edit time limit, but I hope the forum moderators/admins would allow you to make any edits you think are needed.
     
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    It needs more than a few edits. It is almost incomprehensible...
     
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  7. W4HWD

    W4HWD Platinum Subscriber Platinum Subscriber QRZ Page

    That was alot and hard to digest.

    Simple question:

    So do I need to bond my rig and tuner ground terminals (both DC powered off the same Astron power supply) to the ground lug on the power supply or amplifier (both of which plug into the wall)?

    A simple “yes” or “no” will do.
     
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    upload_2020-5-19_18-32-0.jpeg
     
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  9. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Not an option. He would need to just create a new thread and ask this one to be deleted, but all the replies would go away with it.

    You can take DAYS to write an article for QRZ.... but you only have 30 minutes to edit it once it's posted.

    On really long pieces like this, it's always best to write the article, read and re-read, print it out and read it some more - have a friend read it - whatever - before ever hitting "reply". The second you do that, the clock is ticking. We do not have an option to "enable post-30-minute" editing for users.

    Dave
    W7UUU
     
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  10. WA7ARK

    WA7ARK Ham Member QRZ Page

    Yes.

    I bond my Rig (IC7300) to my tuner chassis (PalStar) to my amplifier chassis (AL80b). That bonding wire also visits other shack accessories, including a DELL tower computer that is plugged into the Rig using USB. That bonding wire also runs though the shack wall to the entry panel where all my outside coax runs are grounded before they enter the building. The entry panel is also bonded to the electric service grounding system (Ufer, in my case). A separate bonding wire runs from the coax entry panel to the tower base.

    But hey, according to our resident expert, I don't have a clue as to what I am doing, and he thinks I don't own or have ever read this:
    upload_2020-5-19_16-57-48.png
     
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