Industry Forums > Wireless Service Providers > Proper Grounding Techniques for CPE's, AP's and Antennas?

Proper Grounding Techniques for CPE's, AP's and Antennas?

*kicks the door to the rabid dog kennel open*

release the hounds!

reply to popcorrin
Please expect some rather passionate responses

reply to popcorrin
Q1: "I've searched the forums and while there are posts on the subject, there is nothing concrete on the best practices to use."

A1: Our forum member robbin posted a link to Motorola document from which I copied an excellent diagram and marked it up with some comments: »Re: [Bus. Ops] CPE grounding 'Poll'

Q2: "Is it important to use surge suppressors on both the coax going to the antenna and on the cat5 no matter where you are installing?"

A2 part1: You must protect the customer premises from surge event due to moral obligation if not regulations! Usually it is just a single CAT5 cable going to indoor router, so use a decent PoE surge protector near the entry point at low height close to building safety ground so you can bond using a short strap.

A2 part2: If you are willing to sacrifice the radio, you can skip both coax and PoE surge protectors at the radio end - just make sure your setup can't be blamed for any building fires!

But if you want the radio to survive even a modest surge from a far away lightning storm, it must be in a properly shielded enclosure and you must surge protect every single entry point. That includes all RF ports, Ethernet data pairs and any PoE power conductors. Now the grounds of all the protection devices need to be bonded together - but remember this does not include PoE negative pair!!!

Now the combined bonded "ground" of the protectors need to dissipate the surging electrons through tower body or building/silo frame, or an appropriately large conducting surface routed properly to real ground.

Q3: "If this is the case, why doesn't all the eqpmnt that is sold come standard with the proper surge suppressors."

A3: Due to lack of regulations, satellite and radio equipment manufacturers do get away with providing a vague suggestion to "ground" equipment.

Pobability of losing outdoor equipment to a surge event is 1 in 100 while starting a fire is in the 1 in 100,000 range, both seems so low that we have become complacent. More effort is spent educating golfers or scouts who have less than 1 in 1,000,000 chance of dying in a thunderstorm!

Q4: "When installing a cpe on the roof of a house does a person need to run a grounding cable to earth from the CPE? If so what gauge should it be and what would constitute a sufficient grounding rod?"

A4: Re-read A2-part 2 above. You need an appropriately large low inductance conducting surface to divert many many joules from even a nearby strike! A long run of "grounding wire" may fail in that crucial task even if meets electrical safety code!!! This is where some understanding of lightning and physics is important.

Q5: "If you have surge suppressors, is proper grounding that important. Vice versa, if everything is very well grounded are surge suppressors that important."

Surge suppression is very important to protect customer equipment inside the house, and optionally to protect the radio on the pole. Simple grounding is not sufficient for either task.

Proper grounding is usually the easiest way for surge protectors to divert all those electrons but do remember that avionics in aircrafts are required to be fully protected from even direct lightning strike without usage of a "grounding wire" !

Q6: "If you install an access point on a concrete structure such as a grain silo what would be the best way to ground it. I have read that grain silos are considered Ufers and can be grounded to? How would you attach a ground to concrete?"

The mounting hardware is often sufficient to bond your equipment to typical concrete structure, but you can also use stainless strap tightly fitted around silo body.

Wow, thanks for all the great info EMC-guy!

As far as cat5 surge suppression goes, you would suggest putting a suppressor at both ends( one near the customers equipment and one near the radio?

I'd just put the protector at the building entrance.

That is what is required by code, at least in the USA.

reply to popcorrin
How important is it when grounding the eqpmnt that the ground point ties into the existing building ground?

For instance, let's say you are installing the cpe on a metal pole in the customer's yard a good distance from the house, is it imperative that a ground wire is ran from that cpe to existing building ground? Wouldn't the metal pole provide a good earth ground?

What about when installing the eqpmnt on a house. Is it a bad idea to install your own ground rod and ground to that?

One thing that irritates me is that I have bought a few cpe's that seem designed with no provisions for grounding or surge suppression. Nanostations for instance.
I feel that the proper eqpmnt and documentation should be included with these products.
It would seem to me that with the way most of these products are designed that the majority of people aren't bothering with proper grounding.
Also, surge suppression items don't seem to be that common for vendors to carry. Some major vendors carry very little in the line of surge suppression which makes me think that they don't sell much along those lines, which then makes me think that people aren't using the proper grounding and surge suppression because it's not cost effective?

reply to popcorrin
It is very important to tie two different ground potentials together. Failure to do so will result in a difference in potential, which could (and does) result in damaged equipment and pose a threat to life itself.

Plus, if an event occurs you want ALL electrical items to be at the same potential. Everything rises together, everything falls together during the event, so damage is minimized. It is when you get some devices rising and some falling (voltage up on some voltage lower down on others) at different times, you get damage.

It is best to properly install a protector on the antenna jack of the radio just as it enters the radio. Properly installed means bonded to a known, functional electrode system. Easier to do on a tower site than a residential install, which is why most of us just ground at the building entrance (ground/bond the PoE runs before they enter the building).

It is less costly to protect the POE run than it is to install coaxial protectors and then install poe protectors and then install all of the required bonding materials to get everything at equipotential....

Some CPE's have built in POE protection at the CPE. Some do not. It's no big deal, so long as you bond the POE before it enters the building.

Keep in mind that my whole post has centered around CPE protection. Your AP sites should always have much more bonding and grounding and everything as the risk is higher there, as usually they are mounted on higher points, plus the failure of a single AP could cost you much more money (due to the number of customers it affects) than the failure of one CPE.
--
"No job is so important, and no service is so urgent that we cannot take the time to perform our work safely."
-- AT&T, Your World, Destroyed.
--Safety One Tower Rescue Certified
--LLigetfa:"Wimax is like teenage sex. Everyone talks about doing it."

The only product that I have seen that is designed for grounding the cat5 at the building entrance is the one for the canopy line.

I have seen a few power injectors though that have surge suppression built in. These of course are to be used indoors. Is there a problem using these instead, I know most of the suggestions are to use surge suppression outside right before it enters?

reply to popcorrin
»www.transtector.com/ProductData?···Ethernet

They make a whole line of POE protectors for both manufacturer specific applications, and other applications.

reply to popcorrin
I believe polyphaser makes some as well.

reply to popcorrin
Came back to browse for a day and saw this topic near and dear to my heart. Lots of good information posted in previous grounding threads here.

Steve

reply to AMD Phreak

said by AMD Phreak:

*kicks the door to the rabid dog kennel open*

release the hounds!

reply to popcorrin

reply to popcorrin

reply to popcorrin
Would bonding your equipment to a safety ground inside an existing outlet box be acceptable?

reply to popcorrin

reply to EMC_guy
Why is Cat5 ground not to be bonded to "safety"? Define "safety"? This is not an objection, I'm trying to learn something from this thread as well.
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if you fail to plan, you plan to fail