Grounding of an outdoor omni wifi antenna

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Grounding of an outdoor omni wifi antenna

Postby JimmyCage » Tue Oct 25, 2011 6:31 pm

Hi,

What I want to do : Mount an outdoor Omni-directional antenna on a house and connect it to a high power access point, which is inside the house, using a 40 feet LMR-400 Coaxial cable.

I'm about to install my first wifi antenna on a house for a customer. I'd like to do it right. At first I thought it was going to be easy. I saw some diagrams on manufacturer's websites. I saw some jobs done by amateurs online. It looked pretty easy. But then I stumbled upon a website with good information on the NEC (National Electrical Code in the USA) grounding requirements for installing antennas and coaxial cable : Satellite System Grounding (DBS Install) :
http://www.dbsinstall.com/diy/Grounding-1.asp

It made me think about covering my butt a little more, in case something would happen after the installation.

According to the NEC , the equipment should be grounded, so if something happens (like if a powerline falls on the equipment), it won't be a hazzard for humans life (cause a fire; electrocution) because it will be grounded. It's also a good way to discharge static electricity build ups. It makes sense. The NEC code requires the mast (or mount) of the antenna to be grounded. Plus they require that the coaxial cable is grounded. They require that the mast and the coaxial cable are grounded before the point of entry of the coax cable into the house (so if there's a surge, it won't go in the house, but be dissipated in the ground beforehand). (Note: I don't want to invest in sophisticated direct lightning strike protection.)

I've found some information on how to do this for satellite dishes.
Search for ground in this document (DirecTV dish install guide): http://www.directv.com/learn/pdf/SelfInstallGuide.pdf

My problem is, I don't find any indications that wifi installers are grounding their antenna mount anywhere... It seems that everyone are installing their equipment like they think. Or as the pretty looking diagrams they find on manufacturers websites.

Many company are selling some inline surge arrestors that you put in between two coaxial cables.
Look at "Simple Setup" Option 1 here: (AmpedWireless coax)
http://www.ampedwireless.com/products/apc25ex.html
In that example, the surge protector is inside the house...

My question is : Does the NEC code require, for wifi installations :
The grounding of the antenna mast?
The grounding of the coax cable, outside the house, before the point of entry (that is : put the surge protector outside the house and not inside)?
Do we have to ground to the main ground of the house absolutely? Or is it OK to just drive a metal rod in the ground, outdoor, close to the antenna?

Do you guys have any other suggestions for a first antenna install like this?
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Re: Grounding of an outdoor omni wifi antenna

Postby Barry » Wed Oct 26, 2011 6:12 am

We grounded all our microwave gear just inside the building. Mainly because it was on top of a building, but it also protects the connections from the weather.
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Re: Grounding of an outdoor omni wifi antenna

Postby Thorn » Wed Oct 26, 2011 7:31 am

It really depends on the local and state electrical codes, and whether they have no code, NEC, or some more stringent standard. Start by checking with the building inspector's office for the municipality where you're doing the installation. They should be able to tell you what is required, including whether or not you have to be a licensed electrician, rated for low-voltage installations.
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Re: Grounding of an outdoor omni wifi antenna

Postby JimmyCage » Wed Oct 26, 2011 8:19 am

Thank you for the answers.

What is a common practice among most wifi installers? Do they ground the coax before or after it enters the building? Do they ground the antenna mast also (or just the coax cable)?

Also, do you guy crimp you own LMR-400 cables? Or do you prefer buying them with the connector already installed? I know how to crimp a connector on a RG59 cable, but is it possible to do it reliably, on our own, for LMR-400 coax?
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Re: Grounding of an outdoor omni wifi antenna

Postby Thorn » Wed Oct 26, 2011 8:53 am

For me, it depends on the install, and where the nearest ground point is located. Although to tell you the truth, I haven't done an exterior install in at least two years. There just hasn't been any call for it here.

As far as the LMR-400 or any LMR-xxx, I crimp my own. It's a lot cheaper than buying them per-installed. Of course, like with a lot things, doing it right requires the correct tools. You can't do it with a pair of pliers and a prayer, and expect that you'll get the right impedance. I have two RF Industries RFA-4005 crimping tools, one equipped with a RFA-4005-1 die set, and the other with a RFA-4005-2. They are priced at about $225-$250 each. Extra dies cost about $35-$50 per set. If you want to just by one tool, and two die sets, it will only cost about $300 as opposed to approximately $500, but swapping the dies multiple times on a job gets to be a pain in the neck real quick.

Also, get the correct coax cable-cutters and strippers. LMR cable is expensive stuff, and you'll waste a lot of it -or blow the installation- if you don't have the right tools.

(No G8t, not THOSE kinds of strippers!)
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Re: Grounding of an outdoor omni wifi antenna

Postby JimmyCage » Wed Oct 26, 2011 6:19 pm

Thorn wrote:For me, it depends on the install, and where the nearest ground point is located. As far as the LMR-400 or any LMR-xxx, I crimp my own. It's a lot cheaper than buying them per-installed.


Thanks for the tips man. I appreciate it. I'll look for a good crimping tool then.
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Re: Grounding of an outdoor omni wifi antenna

Postby criswat » Mon May 21, 2012 2:23 am

The information you shared in the post about the antenna is really very nice. I am glad I visited here and come to know about it. I have gathered a huge knowledge being here. I will definitely look forward to it while installing it.
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Re: Grounding of an outdoor omni wifi antenna

Postby kupa » Wed Aug 22, 2012 5:15 am

Thorn wrote:For me, it depends on the install, and where the nearest ground point is located. Although to tell you the truth, I haven't done an exterior install in at least two years. There just hasn't been any call for it here.

As far as the LMR-400 or any LMR-xxx, I crimp my own. It's a lot cheaper than buying them per-installed. Of course, like with a lot things, doing it right requires the correct tools. You can't do it with a pair of pliers and a prayer, and expect that you'll get the right impedance. I have two RF Industries RFA-4005 crimping tools, one equipped with a RFA-4005-1 die set, and the other with a RFA-4005-2. They are priced at about $225-$250 each. Extra dies cost about $35-$50 per set. If you want to just by one tool, and two die sets, it will only cost about $300 as opposed to approximately $500, but swapping the dies multiple times on a job gets to be a pain in the neck real quick.

Also, get the correct coax cable-cutters and strippers. LMR cable is expensive stuff, and you'll waste a lot of it -or blow the installation- if you don't have the right tools.

(No G8t, not THOSE kinds of strippers!)


Exelent,thanks :)


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