Site grounding

[rebelwireless]

This is a little electrical engineering 101

tower is a resistor and goes to ground separately

ground cable is a resistor and goes to ground separately

ethernet cable is a resistor and goes to ground separately

each resistor (tower, ground cable, ethernet cable) that goes to ground causes a voltage dividing.

12v line, 4k resistor on end, 2k resistor in middle (creating a 2:1 ratio). If you connect a multimeter to the ground and touch the positive side, you will see 12v, move the ground lead to between the two resistors and you will see 8v, now read on each side of the centered resistor and you get 4v. That is exactly what is happening with ground potential. The 'missing' voltage is eaten by the resistor. If this is just static electricity, it's probably going to take a while to burn up the radio, but if you get a lightning strike or even just clouds passing over quickly, the resistor/radio will eat more and more load until it fails catastrophically.

This also means that the opposite ground (the less effective ground) can actually look like a positive lead (because of the voltage dividing affect), so you will be putting load on the radio. Bond the grounds and the radio will no longer have to carry the load. REALLY good grounding avoids the need to bond the grounds.

[lligetfa]

12v line, 4k resistor on end, 2k resistor in middle (creating a 2:1 ratio)...

We are dealing with a lot more than 12V and the amps will factor in as well.

I really don't understand why you say "REALLY good grounding avoids the need to bond the grounds". Bonding provides a bit of "bird on the wire" like the guy in this video.
https://www.youtube.com/watch?v=9tzga6qAaBA

[rebelwireless]

The 12v was just an example at familiar voltages and can be proven with available parts.

If you have good grounding on both sides, you minimize difference potential. For example, making sure the transformer has a good ground as well as tower means you don't need to bind the transformers ground to the towers ground. If the transformer has a poor ground, you can get a potential difference, you could bond that ground to the tower to eliminate the potential, better to improve the ground like Chris's example above.


Also, this phpbb then kinda sucks on my phone.

[sirhc]

Bonding ALL ground systems together is the best way to eliminate ground potential differences.

Even if your tower ground is good and your service ground is good there will still be a potential difference which your Ethernet cable then becomes the point of equilibrium which is a BAD thing.

Plus the way lightning works which is counter intuitive to what people think where as the positive charge builds up on the surface of the ground in the top-soil above the clay sub-soil. If the ground rod that does not penetrate the clay sub-soil about 18" is all but useless especially when the soil becomes wet unless your region of the country has a high content of conductive minerals like iron sulfate fround in coal mining regions which makes your well water smell like rotten eggs. The more ground rods you have spread as far apart as possible in different directions all bonded together can allow that positive charge to be dissipated before lightning can occur. If the positive charge is eliminated then an equal amount of the negative charge is remove from the atmosphere.....think of it as the Yin and the Yang of lightening where there must me an equal opposite force or it can not exist.

https://www.youtube.com/watch?v=pHV6u-RwroY

[lligetfa]

Bonding is not only desirable, it is an NEC requirement.

Oh, and Chris, lightening is something you put in your hair. Mind you, lightning could also lighten your hair.

[WHT]

Uhh....Bonding to ground has never been an NEC requirement.

[WHT]

Normally I put the #6 green wire's lug under the clam-shell nut then when I am done tightening it I spray it with cold galv.

Not a bad idea to protect the hardware. Lot of people cringe at painting copper with zinc rich paint...the worst will happen is the zinc will galvanicly erode away.

[ISW-Mike]

Whenever you have a mix of metals....you can actually make your own 'inert' jumpers. Steel is very easy to plate with copper, and there isn't much that doesn't adhere to copper. There are numerous sources for getting copper plating materials....the most simple is just voltage and a piece of pretty copper and of course an electrolytic solution. You can plate it as long as you want, and it will just continue to build up on the steel. Once you build it up nice and thick, plate the other half of the jumper with nickel. Use Stainless is another option (not for plating - least likely to interact).

If going copper to galv steel, you can easily strip off galv w/ acid or a sand blaster. Start by duct taping 1/2 of the galv steel to keep the galv plating in place. On the untaped stripped side, place another piece of duct tape over about 1/2" of the virgin steel. This will keep it from getting copper plated. Once plated and tape removed, hit the center unfinished steel with a light steel wool removing any surface rust that may have built up, clean off the dust, and immediately coat with a bare metal primer. Once installed you can hit the whole thing with paint or a clear coat. You will not have to worry about the metals corroding each other.
You can get 24k gold plating solutions too....if you have money just burning a hole in your pocket :)

[sirhc]

PEOPLE I SPENT SOME TIME AND UPDATE POST ONE OF THIS THREAD, PLEASE TAKE A MOMENT AND RE-READ IT!

[dcshobby]

Hey Chris,

Can you post something about the benefits of running Fiber and AC or DC power up to a Netonix switch from the base to the antennas and then short ethernet runs from the Netonix to the radios on top? This seems it would take care of much of the potential ethernet issues and grounding problems. Would there be any suggestions for grounding the power cable from the top to the bottom in this situation?

Thanks