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Author Topic: Proper station grounding. Daisychain or independent grounding question  (Read 378 times)

N2RRA

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Hello everyone,

We are going to go over properly grounding your station taking a consensus, because I need a little refresher. Much like the NEC book tends to get revised every few years I’m curious to find out what the consensus out there is to properly grounding your station not only for electrical shock and lightning strike  prevention, but of course none other than RFI and EMI protection.

So here is the big question.

How many of you have daisy chained your grounds between equipment before going to your single point ground rod, or independently ground strap each piece of equipment to a ground bar that goes to a ground rod?

As far as materials used I always use flat ground straps. I use everything from three-quarter inch, 1 inch and 2 inch wide flat copper ground straps and braided ground flat straps. For me there is no other adequate substitute, but if you have to of course electrical conductors can be used.

So who will say which is the best method?

Thank you for all your input in advance.
« Last Edit: March 17, 2021, 03:05:05 PM by N2RRA »
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W6QW

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« Last Edit: March 17, 2021, 03:58:02 PM by W6QW »
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WA9AFM

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Get a copy of "Grounding and Bonding For The Radio Amateur" by Ward Silver, N0AX.  It cover electrical safety, RF management, and lightning protection; they are all related.
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N0JX

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The simple answer to your question:
Do not daisy chain (serially connect) your equipment to a ground wire. Connect them all as close as you can to a single point ground. This prevents ground loops and voltage potentials between the equipment ground connections.
« Last Edit: March 18, 2021, 05:37:42 AM by N0JX »
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K0UA

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"Consensus on grounding".  Not that there is funny, I don't care who you are.
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73  James K0UA

KF5LJW

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Just about every ham daisy chains their grounds and lost in a Ground Loop. It comes from Elmers using 1950/60 outdated practices. It comes from th eold days when homes used 2-wure grounding and topology. Back then placing a ground rod outside the shack was best practice. Today it is deadly and guaranteed to generate RFI/EMI.

Today it is really simple, NEC 250-94 requires Single Point Ground. Bring your coax in with the AC Service and bond everything to the same point. All you bing in th ehouse is your coax and a single #6 AWG for your Station Safety Ground for the DC equipment. 

Two excellent free articles that are up to date and will walk you through it.

https://www.repeater-builder.com/tech-info/bonding/amateur-radio-bonding.html
https://www.mikeholt.com/instructor2/img/product/pdf/17LED-1498-sample.pdf

The picture below pretty much sums up what goes on outdoors. Inside just a ground bar so you can connect a dedicated safety ground for each piece of equipment without a 3-wire power cord with ground.


« Last Edit: March 18, 2021, 10:53:49 AM by KF5LJW »
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W6QW

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@KF5LJW

The NEC 250.94 that you refer to is a shock and safety standard and can be counterproductive to EMI/RFI mitigation.  For instance, the use of a circular bonding wires allowed per NEC adds unwanted RF return current impedance compared to flat-plane current return straps.  Accordingly, implementation of a robust communications system in the field requires a knowledge of what is not only important to the likes of  ITIC or IAEI constituents but RF telecommunications constituents, as well.   Here is a tutorial that will help with the understanding of proper grounding techniques for RF EMI control:

https://m.eet.com/media/1114898/duff_ch_5.pdf
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KF5LJW

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@KF5LJW

The NEC 250.94 that you refer to is a shock and safety standard and can be counterproductive to EMI/RFI mitigation.  For instance, the use of a circular bonding wires allowed per NEC adds unwanted RF return current impedance compared to flat-plane current return straps. 

Have you read any of my work? Your are correct NEC allows you to use wire for a ground. However you can also use something else like a real ground buss like all commercial sites use called an Equipotentiality Ground Plane where the impedance between any two points is essentially 0-ohms.

Example all the Antenna Discharge Units bond directly to a buss bar, there is no wire. AC/DC circuit bond to the same place. When you have no current or voltages in ground conductors, you have no RFI/EMI. No reason to make it complicated.

Myself an an army of RF engineers and hams to 30 years for NEC to make Single Point Ground the law. NEC is minimum requirement. Instead of a screw type buss bar using wire, can be replaced with a buss bar eliminating the noisy wire. Inside the shack everything is a safety ground, and you want as high of impedance to RF as you can possible have.

The biggest issue for hams is placing their radio in a ground loop, and using a DC power supply with a galvanic bond across primary to secondary. When you place a ground rod outside the shack and bring you coax in with it, you are in a Ground Loop and lost the RFI/EMI battle. That is just a minor problem, the real concern is the extreme danger it places you in. NEC 250-94 closed that loophole.
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W6QW

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Today it is really simple, NEC 250-94 requires Single Point Ground. Bring your coax in with the AC Service and bond everything to the same point. All you bing in th ehouse is your coax and a single #6 AWG for your Station Safety Ground for the DC equipment. 


The point to my challenge to your above statement is that it incorrectly suggests that implementation will mitigate the potential EMI/RFI situation.  That is not necessarily correct and that is why I suggested that short reference tutorial as an educational opportunity.

I am very familiar with NEC 250.94.  As NEC only addresses the requirements to meet the safety requirements of NFPA, the utilization of apparatus such as equipotential bonding busses and planes that you mention are meant to address electrical safety behavior alone.  NEC does not care about RF - that is why the engineering communities have developed standards and practices that specifically address RF behaviors which your NEC referral does not. While NEC does not preclude the application of standards from IEEE, ITU, etc that have been developed to address EMI physics, it should not be used as the method to mitigate such. That is why your suggestion and pictorial could be misleading.

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N2RRA

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"Consensus on grounding".  Not that there is funny, I don't care who you are.

There’s always gonna be a moron troll with stupid responses. Now, that there is funny and I don’t care who you are.
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N2RRA

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Re: Proper station grounding. Daisychain or independent grounding question
« Reply #10 on: March 20, 2021, 01:50:28 PM »

Thanks for all the consensus and opinions on grounding your station. Appreciate those who all gave intelligent valuable responses. All the links were noted and looked into.

Seems there’s still a little debate on proper grounding and bonding and the reason why I brought this topic up was, because I feel the NEC electrical code on binding relates to electrical installations, but is not entirely a model method when you’re installing amateur radio station in line. It always gets a tad controversial.

There are links to web pages where I found discrepancy’s and were on the right track, but made minor mistakes that I saw as counter productive. As in 3ft to 6ft. 1/2” copper tubing running underneath their desks with a million #12ga. wires all over the place unto the tubing creating a ground loop. Then running #6ga. wire up to 50+ft. away to a ground rod in which I know most don’t even buy the largest ground rod obtainable like a 3/4” x 10ft. long and get ithe full 10ft. Into the ground.

That’s why I mentioned a ground bar in the beginning and flat copper straps for a reason that no one really mentioned. In my opinion it’s a crucial component in the system.

Anyway, great suggestions and good topic to go over. There was a little debate, but debates are good refreshers.

73
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