Proper Grounding Methods


#1

There are always some interesting debates on the proper method of grounding radios. Which method do you perform and why.

I have always been under the impression to do the following.

Radio - Ground to Tower via ground wire to metal mast or grounding junction for lightning strikes.

For ESD:

Radio----FTP Cable (Coiled at Radio for resistance) — Transient Protector (Ground to Tower) ------------------Transient Protector (Ground Via Building Ground)—POE Port.

But what if your tower isn’t R56 or is a water tank or non grounded object to which your radio mounts on. Do you run a ground wire up along with the FTP?

Thoughts?


#2

Let’s see if I can explain it they way I understand it…

Let’s start backwards…:-

For proper ground configuration. Every location needs two grounds (Electrical Ground, and Earth Ground). And both(all of them if multiple exist) of these Two Grounds should be bonded together.

Every tall structure with any kind of lighting protection will have some sort of a Earth Ground on it.

Grounding the Radio, is normally protection for any kind of lighting NOT to go thru the radio (to the electrical ground ).

Shielded cable is grounded simply for ESD protection (not lighting, wire is too thin, it will act as a fuse).

If the Earth Ground and System(Electical) Ground are not bonded together, then you will loose ethernet ports due to electricity flowing between the two grounds via the cable and Electronics…

Moral of the story is:-

  1. Find the Earth ground on the structure, and ground your hardware, radio, mast, surge protector to it.
  2. Find the Electrical ground and make sure your electronic equipment is grounded to it.

MOST important: Check the resistance (ohm meter) between the electrical ground and the earth ground, and make sure that it is less than 5ohms… otherwise you are asking for trouble.

BTW (Water Tanks, are metal structures, they are most likley using all of the structure as the earth ground).

I have seen folks run a separate ground wire (earth ground), I believe it is simply because they don’t / cannot trust the quality of the earth ground at the top of the structure, and they want to make sure that they earth ground at the bottom of the structure is connected (very low resistance) to the earth ground at the top of the tower.

Also, coiling Ethernet wire at the top, won’t do much to the resistance, it could create some impedance … but overall in my opinion it does not contribute anything to the ‘protection’ of the system, other than you have some excess cable…

:smile:


#3

Thanks Faisal,

Any recommendations on surge protectora that you use? Should I be placing one at the top and bottom of the cable run?

Thanks


#4

Good Question Kevin,

The jury is out on this one… So, the thought process behind the two surge protectors (one at the top, and one at the bottom) is to get the ‘surge’ to exit the closest point, without travelling down the wire itself.

So, base on this, the next question becomes, how tall is the tower ? and how long is the cable run between the top and the bottom ?

Most of our stuff is on Rooftops, as such the cable runs are not very long, we put a (ethernet) surge protector Either outside or inside before the switch.

Though, we recently installed a 6ghz Licensed link (using LMR 400) cable, and we did what was recommended by the MFG. a gas tube surge protector near the radio, and one near the IDU…

The key thing is to make sure that both (all of these surge protectors) are grounded to a common ground… and they don’t have any (less than 5ohms) differential between them…

(For Ethernet surge protectors we have used a variety of them, no particular affinity to any one on them… get one that will work, i.e. pass the POE, and is in the form factor that you can work with)

Regards


#5

BTW, Kevin, I just read your profile… looks like you all do contract installs… If that is the case, then do it by the book (regardless of sense and sensibility) … Here is a nice doc on this… http://www.reeve.com/Documents/Articles%20Papers/AntennaSystemGroundingRequirements_Reeve.pdf

The primary reason why I am saying what I said above is because you need to cover any potential liability … if you do it by the book and stuff goes poof it is act of god… but if you don’t do it by the book and the stuff goes poof then they may come after you !

:slight_smile: