Antenna/Coax Grounding

[Guest NotMakingTrouble]

Browsing the interwebs reveals there is a wide variance in opinion about how to properly ground an antenna/coax system. Asking about it seems to be a good way to start a food fight. That's not my intent here; I'm just trying to nail down "right" in my effort to keep the installation safe.

As my point of reference I'm starting with this interpretation of the NEC. and repeated in the articles found here and here. My takeaway is the grounding goes to the rod at the service panel. What I'm not sure about is the need to run two separate wires to the rod as is shown in the illustrations in the video and articles referenced above. They show the wire from the antenna mast going to the rod and a totally separate wire going from the arrestor to the rod. What I'm wondering.... my question is... can those two wires not be connected together so that a single wire runs to the rod? Illustration of my specific situation below.

The interpretation of the NEC in the above references suggests I need two ground wires running side-by-side the long (and expensive) distance to the rod. Illustration here. What I'm wondering about is whether two separate wires are actually required. Can I not tie the two wires together at the mast as illustrated here?

Thanks in advance for any advice you're willing to share.

 

[OffRoaderX]

No matter what someone posts, someone else is going come along and post the opposite- and both will decree that they are correct because they took a test and are therefore "experts".

Good luck.

[WRYZ926]

Yes there are many opinions on this subject. Your best bet is to follow NEC when it comes to grounding your antennas, coax, and radios.

Here are a couple of other links that will be helpful for you.

https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

https://www.arrl.org/grounding

GMRS and amateur radio antennas, coax and equipment require the same grounding techniques.

[SteveShannon]

15 minutes ago, Guest NotMakingTrouble said:

Browsing the interwebs reveals there is a wide variance in opinion about how to properly ground an antenna/coax system. Asking about it seems to be a good way to start a food fight. That's not my intent here; I'm just trying to nail down "right" in my effort to keep the installation safe.

As my point of reference I'm starting with this interpretation of the NEC. and repeated in the articles found here and here. My takeaway is the grounding goes to the rod at the service panel. What I'm not sure about is the need to run two separate wires to the rod as is shown in the illustrations in the video and articles referenced above. They show the wire from the antenna mast going to the rod and a totally separate wire going from the arrestor to the rod. What I'm wondering.... my question is... can those two wires not be connected together so that a single wire runs to the rod? Illustration of my specific situation below.

The interpretation of the NEC in the above references suggests I need two ground wires running side-by-side the long (and expensive) distance to the rod. Illustration here. What I'm wondering about is whether two separate wires are actually required. Can I not tie the two wires together at the mast as illustrated here?

Thanks in advance for any advice you're willing to share.

 

You do not need two separate parallel conductors. You’re allowed to bond them together where they physically intersect. Understand that bonding is required to be permanent, using connections that cannot be easily undone.  Typical bonding methods include thermite copper welding or crimped connectors, not bolted cable clamps. 
The Mike Holt videos are very good. The Bible for comm site lightning protection is R56 from Motorola, but it’s very complicated and overkill for anyone other than a professional communications technician. 
I really like the succinct approach taken by the Reeve document.  It agrees with the Holt videos well:

https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

 

[WRXL702]

The Motorola R56 Manual Is The Standard Used By Most Public Safety Communication Sites For System Grounding.

Tap / Click On Chapters 4 & 5 To View.

 

https://northgeorgiacommunications.com/wp-content/uploads/2022/05/Motorola-Standards-and-Guidelines-for-Communication-Sites-R56-Manual.pdf

[WRUE951]

  https://reeve.com/Documents/Articles Papers/Reeve_AntennaSystemGroundingRequirements.pdf

 

https://thenecwiki.com/2021/02/article-810/

[WRYZ926]

The reeve.com PDF file must be a good reference considering three of us have posted links to it. 

And nothing will protect your setup from a direct lightening strike. Read through the references we provided and go with what works best for you and still meets NEC. 

PS: definitely unplug everything before hand if you know a lightening storm is heading your way.

 

[Guest NotMakingTrouble]

2 hours ago, SteveShannon said:

You do not need two separate parallel conductors. You’re allowed to bond them together where they physically intersect.

Excellent. Thanks for that.

[SteveShannon]

18 hours ago, Guest NotMakingTrouble said:

Excellent. Thanks for that.

What you’ll probably want to do is place a ground rod at the base of the mast.  The coax will lead from the antenna feedpoint to the lead-in to the house where you will place an antenna discharge unit.  A ground wire will lead back from the ADU to the mast where it and the wire running from the mast will be bonded to that ground rod using a three wire connector. The three wires are: the wire from the ADU, the wire from the mast, and the wire that then runs to the service ground which would be a single buried #6 or greater bare wire.

I would make all of the ground rod connections using either crimp on Burndy style connectors or one-shot thermite connections.  
But I’m in Montana, unfamiliar with your local electrical inspectors, and with only a line drawing to work with. The only things I’m certain of are that your mast needs a ground rod, that ground rod must be bonded to the service ground, your ADU needs to be connected to your service ground, and I believe the NEC allows the wire from your ADU to be connected to the wire from the mast to the mast ground rod.

@WRUU653 - what would you recommend?  

[WRYZ926]

I might have over did things in my setup. The service ground is in between my mast and where the coax cables enter the house. I put a ground rod at the base of the mast and another right below where the coax bulk head is. I tied both grounds rods to my service ground with 6 gauge wire. All of the ADU's are grounded to the rod at the entry point.

I made my own bulkhead using metal plates and long bulkheads (to get through the wall) along with a piece of 1/4" 20 all thread for grounding. I ran grounds from all my radios and my tuner to the all thread which is also connected to the ground rod just outside.

[SteveShannon]

31 minutes ago, WRYZ926 said:

I might have over did things in my setup. The service ground is in between my mast and where the coax cables enter the house. I put a ground rod at the base of the mast and another right below where the coax bulk head is. I tied both grounds rods to my service ground with 6 gauge wire. All of the ADU's are grounded to the rod at the entry point.

I made my own bulkhead using metal plates and long bulkheads (to get through the wall) along with a piece of 1/4" 20 all thread for grounding. I ran grounds from all my radios and my tuner to the all thread which is also connected to the ground rod just outside.

Nice!

[WRUU653]

1 hour ago, SteveShannon said:

@WRUU653 - what would you recommend?

You can use one wire or two. All roads need to lead to the service ground though. As the video mentions you can't run to two separate and separated grounds, they need to be bonded. bonding is different than grounding, bonding all grounds together removes any potential between grounds. This is why you don't use one ground rod at the service and another at the mast without them being connected ("bonded") together. 

[Guest NotMakingTrouble]

1 hour ago, WRUU653 said:

This is why you don't use one ground rod at the service and another at the mast without them being connected ("bonded") together. 

Which is why I wonder about the need for a rod at the base of the mast. Why not just run the wire from the mast directly to the rod at the service panel?

In the video linked above as well as the associated illustrations there is no indication of a second rod.

[SteveShannon]

5 hours ago, Guest NotMakingTrouble said:

Which is why I wonder about the need for a rod at the base of the mast. Why not just run the wire from the mast directly to the rod at the service panel?

In the video linked above as well as the associated illustrations there is no indication of a second rod.

It's better to have a ground rod right there (but it must be bonded to the service ground) and that's certainly what the ARRL would recommend, but there's no requirement to do so.  Remember, electricity takes the path of least resistance (but it divides itself amongst all paths). If you have a short wire going to your house and a long wire going to your service ground, a portion of the energy could easily go towards the house.

So, I would, but it's really up to you.

[WRUU653]

1 hour ago, Guest NotMakingTrouble said:

Which is why I wonder about the need for a rod at the base of the mast. Why not just run the wire from the mast directly to the rod at the service panel?

In the video linked above as well as the associated illustrations there is no indication of a second rod.

 You don't need a second rod. If the mast is mounted to the home I probably wouldn't have a second rod. If I had a tower that's another story. Each situation can be different depending on where and how your set up is so I try to avoid absolutes but the links @WRYZ926 included do a great job of covering different scenarios. You can find the relevant codes in the NEC 810.21, 250.52 and 250.70. 

[WRXB215]

Keep in mind that the ultimate goal is to keep the lightening outside of the living space. And while you are doing that, don't introduce any ground loops.

[WRYZ926]

1 hour ago, WRXB215 said:

Keep in mind that the ultimate goal is to keep the lightening outside of the living space. And while you are doing that, don't introduce any ground loops.

I have thought about a fused link between the ground post on my bulkhead and ground rod.. Either way, I do always disconnect everything when a lightening storm approaches. Everything els will help with near strikes and for static discharges.

[WRUU653]

2 hours ago, WRYZ926 said:

I have thought about a fused link between the ground post on my bulkhead and ground rod

It sounds like what you have is good if I'm understanding it. You don't want to fuse a ground because if energy can't go to the ground it will go somewhere and that may not be where you want it to go. Side story to illustrate this is people using surge suppressing plug strips and plugging them into an older non grounded outlet. The plug strip suppression goes to ground when it sees a surge and if the ground is not there the energy has to go somewhere and I have personally witnessed these plug strips having caught fire in a non grounded situation. Like @SteveShannon said electricity will take the path of least resistance which is why we want to help it go somewhere safer. I have a surge suppressor for my service panel as well as plugs throughout the house for the very reason that what may not be fully captured by one can be captured by another down stream.

[WRYZ926]

@WRUU653 I will leave my setup as it is. All of my ADU ground go directly to the ground rod and I have a separate wire from the 1/4" 20 all thread to the ground rod.

I was only thinking about keeping any lightening from coming in on the 1/4" 20 all thread the all of my stations are grounded to. The all thread goes thru the wall and then down to the ground rod.

[SteveShannon]

28 minutes ago, WRYZ926 said:

@WRUU653 I will leave my setup as it is. All of my ADU ground go directly to the ground rod and I have a separate wire from the 1/4" 20 all thread to the ground rod.

I was only thinking about keeping any lightening from coming in on the 1/4" 20 all thread the all of my stations are grounded to. The all thread goes thru the wall and then down to the ground rod.

Lightning is capable of jumping the gap from the earth to the sky. The gap in a burned fuse would just be ionized fuse metal and highly conductive. Watch a lineman open a switch under load sometime and you’ll immediately understand why fuses can’t interrupt lightning. The contacts would have to operate fast, open far, and something would need to quench the arc. 
However, I’ve heard there are lightning arresters that incorporate inductors to present greater impedance to the rapid onset of voltage along the center conductor of coax. I don’t know anything more about them. When I heard about them I thought I needed to follow up but I didn’t. Sorry. 

[WRYZ926]

I won't worry about changing anything with my setup then. I did use terminal rings to connect my grounds inside to the all thread along with a wing nut so I can always just disconnect them when needed..