Quick grounding question

[sallen07]

OK so I am in the very early stages of *thinking about* putting up a mast with a couple antennas and I want to validate my understanding of grounding requirements. (And yes, I've looked at NEC). My office (and 'shack', such as it is right now) is located at the opposite end of our house from where the power enters (and where the current ground rod is). I know that a mast will require a ground rod, and that the two ground rods need to be bonded together. Is doing so really just as easy as running a 6 AWG ground wire around the back of the house between the two and burying it? Or running it through a conduit mounted on the outside of the house?

 

[mc48]

Search Mike Holt, grounding and bonding for help.

 

[wcsd45]

Without intent to be evasive, my instinct was that grounding did not lend itself to quick question. Recommend ARRL Grounding and Bonding book. Having worked thru that, I developed design then vetted design with licensed electrician. I have similar situation to yours and because of that went with the design/vet route. My instinct on the ground wire is bury it.

73 and good luck,
Chuck KC9QBY

 

[lbashaw]

Similar situation. went to one of the "box" stores and purchased an 8 foot 3/8 diameter copper rod and drove it into the ground closer to shack. I used 4 AWG cable. Even with that and protectors in-line, I still disconnect antennas during storms.

 

[prcguy]

I'm not so sure the mast needs to be grounded but the coax must be as it enters the house. For moderate runs up to 30ft or so 10ga copper is legal to use and if the run is a lot longer you must upsize the wire gauge but I don't have info on what size for how many feet.

You can probably make a legal ground running from the AC entry point of the house to the closest point of the coax using 10 gauge or larger copper wire. If you drive in another ground rod that complicates things requiring the large guage wire to bond that rod back to the AC entry point.

OK so I am in the very early stages of *thinking about* putting up a mast with a couple antennas and I want to validate my understanding of grounding requirements. (And yes, I've looked at NEC). My office (and 'shack', such as it is right now) is located at the opposite end of our house from where the power enters (and where the current ground rod is). I know that a mast will require a ground rod, and that the two ground rods need to be bonded together. Is doing so really just as easy as running a 6 AWG ground wire around the back of the house between the two and burying it? Or running it through a conduit mounted on the outside of the house?

 

[WA0CBW]

Grounding metal antenna masts is described in NEC section 810.15 and antenna discharge units in section 810.20f(3). A ground rod may not be need if there is an intersystem bonding termination. The section describes a number of suitable intersystem bonding points most of which are usually not available in family residential housing. In those cases a ground rod is required. Also if a ground wire cannot be buried it should be protected from physical contact by running it in conduit (plastic) or metal (raceway) which must be grounded at both ends.
Bill

 

[wwhitby]

OP, I had a similar situation at my house. My city requires masts and towers to be located in the back yard. My electrical service delivery point is on the side of the house. So, I put the mast in at the back with a ground rod next to the mast. The mast, coax and lightning arrestors are attached to that ground rod. I then put another ground rod in at the corner of the house, half way between the mast and the electrical ground. I then connect those two ground rods together with 6 AWG bare copper ground wire buried underground. I then connected that ground rod on the corner to the electrical ground with 6 AWG bare copper ground wire. Since the shack is in the room opposite the electrical ground rod, I ran an insulated ground wire through the wall, connecting the copper bus bar where the ground wires for my equipment to the electrical ground.

 

[CharlieWhiskey]

As far as disconnecting your antennas during a storm, keep in mind that commercial two way radio sites and cell towers are installed with grounding and lightning protection which can be duplicated at your home station. No one goes around to those sites to disconnect/reconnect antennas whenever there is a passing storm. The equipment survives all but a direct hit.

 

[prcguy]

This is absolutely true and they do survive direct hits all the time with no damage. Problem is do you want to trench around the entire perimeter of the house, bury hundreds of feet of 500MCM copper cable, install 10ft ground rods every 20ft, retrofit your electrical panel and more? And that doesn't include any arrestors or antenna/phone line specific protection. You can maybe do this for $10k yourself or hire a licensed contractor and spend $30k on up.

As far as disconnecting your antennas during a storm, keep in mind that commercial two way radio sites and cell towers are installed with grounding and lightning protection which can be duplicated at your home station. No one goes around to those sites to disconnect/reconnect antennas whenever there is a passing storm. The equipment survives all but a direct hit.

 

[needairtime]

This is interesting, I was thinking that especially commercial broadcast radio and theoretically commercial 2-way repeater systems should be designed to take direct lightning hits, but I heard that a local ham repeater administrator had their repeater blown out (repeater, cabling, duplexer, whole nine yards) by a lightning strike despite having lighting arresters on the coax. Perhaps the there is indeed more can be done, maybe not on the cheap, to have a radio or repeater system that can be run (or not if not needed) during rainstorms without risking blowing a radio or its cabling/duplexer/etc. even if you don't disconnect it? Any good documentation on how to do this? Or is it pretty much build a shield around the antenna to make the lighting rather strike the shield than the main mast?

 

[prcguy]

A commercial repeater site that allows amateur systems in would usually have the proper tower, power and other grounding/protection to survive direct hits. As long as the amateur puts in equivalent rated arrestors on their feedline and grounds to spec it should also survive. Except for the antenna, which can get blown to bits.

If its an amateur built repeater site then all bets are off and I would not trust it to survive.

This is interesting, I was thinking that especially commercial broadcast radio and theoretically commercial 2-way repeater systems should be designed to take direct lightning hits, but I heard that a local ham repeater administrator had their repeater blown out (repeater, cabling, duplexer, whole nine yards) by a lightning strike despite having lighting arresters on the coax. Perhaps the there is indeed more can be done, maybe not on the cheap, to have a radio or repeater system that can be run (or not if not needed) during rainstorms without risking blowing a radio or its cabling/duplexer/etc. even if you don't disconnect it? Any good documentation on how to do this? Or is it pretty much build a shield around the antenna to make the lighting rather strike the shield than the main mast?

 

[needairtime]

I'd have to get more details on what the site was, I got the impression it was a colocated site with commercial radio but now you're getting me to doubt it. But regardless, any good documentation for someone to build their own home radio system to withstand direct strikes much like commercial radio?

 

[prcguy]

http://keekles.org/~bryan/grounding/R56%20Standard%2081089E50-A.PDF

I'd have to get more details on what the site was, I got the impression it was a colocated site with commercial radio but now you're getting me to doubt it. But regardless, any good documentation for someone to build their own home radio system to withstand direct strikes much like commercial radio?

 

[WA0CBW]

I was a project manager for Motorola for 35 years installing some of the first cellular and public safety sites in the Midwest and I can tell you no amount of "grounding" will prevent a lightning strike. You "ground" to hopefully reduce the damage caused by a strike. The truth is you ground until you run out of money and then you buy an insurance policy. It's much easier to ground a green site than to retro fit an existing site. Retro fitting a residential home can be very difficult and expensive. The minimum you should do is follow the NEC and the ARRL recommendations for grounding. Again that will not prevent a lightning strike or prevent any damage to your equipment. It may reduce damage........ or it may not.

But if you decide to ground the NEC, ARRL and Motorola R56 are good guides to follow.
Bill

 

[wwhitby]

This is interesting, I was thinking that especially commercial broadcast radio and theoretically commercial 2-way repeater systems should be designed to take direct lightning hits, but I heard that a local ham repeater administrator had their repeater blown out (repeater, cabling, duplexer, whole nine yards) by a lightning strike despite having lighting arresters on the coax. Perhaps the there is indeed more can be done, maybe not on the cheap, to have a radio or repeater system that can be run (or not if not needed) during rainstorms without risking blowing a radio or its cabling/duplexer/etc. even if you don't disconnect it? Any good documentation on how to do this? Or is it pretty much build a shield around the antenna to make the lighting rather strike the shield than the main mast?

FWIW, my local PD has a repeater located on a tower in the city. Several years ago, it took a direct lightning strike that did a great deal of damage. We also had a cell tower taken out almost 30 years ago due to a lightning strike. I'm just saying this to say that commercial, public safety , and cellular system can still get damaged or destroyed by lightning strikes.

 

[prcguy]

Depends on who built them and how they were built. If they didn't do all the stuff needed to survive, then it won't.

FWIW, my local PD has a repeater located on a tower in the city. Several years ago, it took a direct lightning strike that did a great deal of damage. We also had a cell tower taken out almost 30 years ago due to a lightning strike. I'm just saying this to say that commercial, public safety , and cellular system can still get damaged or destroyed by lightning strikes.

 

[W5lz]

" I know that a mast will require a ground rod, and that the two ground rods need to be bonded together. Is doing so really just as easy as running a 6 AWG ground wire around the back of the house between the two and burying it? Or running it through a conduit mounted on the outside of the house?"

If you are going to run such a ground, then don't place it in conduit, that defeats it's purpose, you want it to dissipate stuff to dirt. You can have any number of ground rods, but they should all be connected together in a ground 'system'!
Grounding is seldom a -simple- procedure, and to have a 'good' ground it's going to be bigger than you thought to start with. It does pay off though.

 

[prcguy]

Generally the NEC requires primary ground wires as described by WA0CBW in post #6 that are accessible to people, to be run inside a conduit that is also grounded. Every ground wire from the AC electrical panel on a house or commercial building to the ground rod I have seen is run inside flex conduit. Every ground wire from one ground rod to another that is above ground and touchable by people is run inside conduit.

Are you saying to ignore the National Electrical Code? Its all there in the code if you take the time to read it.

" I know that a mast will require a ground rod, and that the two ground rods need to be bonded together. Is doing so really just as easy as running a 6 AWG ground wire around the back of the house between the two and burying it? Or running it through a conduit mounted on the outside of the house?"

If you are going to run such a ground, then don't place it in conduit, that defeats it's purpose, you want it to dissipate stuff to dirt. You can have any number of ground rods, but they should all be connected together in a ground 'system'!
Grounding is seldom a -simple- procedure, and to have a 'good' ground it's going to be bigger than you thought to start with. It does pay off though.

 

[MUTNAV]

I don't think that is what he was saying, I think he meant that it's better to bury the connecting wire so that in increases the surface area in contact with the ground, of course anything that can be contacted by a person should be protected.

Thanks
Joel

 

[MUTNAV]

of course I love to post one of my favorite reference

DTIC ADA239808: Military Handbook. Grounding, Bonding, and Shielding for Electronic Equipments and Facilities. Volume 2. Applications : Defense Technical Information Center : Free Download, Borrow, and Streaming : Internet Archive

I also like to remember that Glideslope towers, in the middle of flat and open airfields, are expected to survive storms with lots of lightning around, and generally they are grounded in accordance with this (or a newer) reference.

Thanks
Joel