Grounding redundancy?

[Alliance01TX]

Grounding

Howdy

As noted in the prior post and a couple of excellent references (Motorola Tower) are well stated. While the NEC is an excellent house wiring reference, but (in my one-sided view) is-not in the RF world and I have historically not grounded my RF grid to the home electrical entry points nor grounding water pipes.

This might sound counter to reason, but using a multi-ground-grid 'isolation' seems to lower the noise levels on HF and get's me more indendent of other man-made noise generators. Ihave the space so that was a main factor....

Agree this is difficult for some station set up's as space and other factors prevent grids,etc....

The main point is tie the grounds together and get the Ohms lowest possible between any gounding points and do use a Poly or like (Alfa Delta also makes great units) arrestors as you might be more likely to get static damage than lighting in some parts of the country....

Be safe!

Thx

Bill

 

[roth_ritter]

Howdy
The main point is tie the grounds together and get the Ohms lowest possible between any gounding points and do use a Poly or like (Alfa Delta also makes great units) arrestors as you might be more likely to get static damage than lighting in some parts of the country....

Agreed, but how to do you tie the grounds together when the two points are at opposite ends of the building or house?

 

[n5ims]

Agreed, but how to do you tie the grounds together when the two points are at opposite ends of the building or house?

Generally the best way to do this is to bury a rather large wire from one of the ground rods around the house to the other. While that will tie the two together, it's best to help make that a continuous ground by placing ground rods every 8 feet connected to this wire connecting the original two rods as well. The 8 feet number is based on the length of most ground rods. If you use rods of different lengths, you should change this value as appropriate. While the shortest path is probably the best, it's not always possible (in my case I have a driveway that prevents this). I've heard that it is best to make a complete circuit (run the wire all around your house). This will allow a good connection even if the wire gets cut in one location. It also helps provide a better ground since all that distance and ground rods provide maximum surface area for the ground circuit to make contact with the soil.

 

[roth_ritter]

Thanks n5ims, that's basically what I'm hearing from another thread on this as well. I guess I've been a little baffled by it, having flash backs from the mantra "short and straight as possible", which in terms of bonding the two is not really possible in a lot of situations. This is where mixups between RF and electrical come into play.

 

[n5ims]

Thanks n5ims, that's basically what I'm hearing from another thread on this as well. I guess I've been a little baffled by it, having flash backs from the mantra "short and straight as possible", which in terms of bonding the two is not really possible in a lot of situations. This is where mixups between RF and electrical come into play.

The along-the-route ground rods are what help to compensate for the "short and straight as possible". It can be pictured as though current paths flow in straight lines between each connected ground rod to help equalize the energy along that entire area. If they weren't connected directly by that large and long ground wire what you would end up with is a difference in potential that could easily fry equipment.

Studies of multiple victums in a ground strike type lightning injury tend to indicate that the injury severity depends on not only how close they were to the strike, but also how they were positioned. If imaginary circles were drawn from the point of the strike to the victim locations (basically showing their distance from the strike) with each point of the victim's ground contact indicated the severity can often be predicted. Folks closer will normally get worse damage than those further away (kind of a "duh" result!). What was interesting though was folks that were standing and had both feet on the same imaginary circle had much less damage than others at the same distance that were standing perpendicular to the imaginary circle. This is believed to be caused by the potential difference being minimal if they were standing on the circle but greater in the folks that had one foot much closer to the strike than their other foot.

 

[Cruiseomatic]

I know this is an old one but here goes,

All those "hams" are stating 8ft. long copper rods. I was always told 6 ft. long rods. I also read somewhere that I would need 3 ground rods that are 6 - 8 ft. long. And what is the deal with Halite (Rock Salt)? Does it really work? What is the REAL truth and how is it that one concept, Radio Transcieving, has SO many different "facts"? Hell, Eham has so many different "opinions" about RF and safety grounding. People claiming to be experts and engineers... What and/or where is the REAL truth?

 

[n5ims]

I know this is an old one but here goes,

All those "hams" are stating 8ft. long copper rods. I was always told 6 ft. long rods. I also read somewhere that I would need 3 ground rods that are 6 - 8 ft. long. And what is the deal with Halite (Rock Salt)? Does it really work? What is the REAL truth and how is it that one concept, Radio Transcieving, has SO many different "facts"? Hell, Eham has so many different "opinions" about RF and safety grounding. People claiming to be experts and engineers... What and/or where is the REAL truth?

6' or 8', whatever floats your boat (or is available at your local supplier). Just remember that when making your ground runs you should pound in a rod each time you reach the length of your ground rod (every 8' for an 8' ground rod or every 6' for a 6' ground rod).

What the salt does is lower the ground resistance. The down side is salt can also speed up the corrosion and make it so you need to redo your ground system more often.

One thing on the "real truth" issue. There isn't one single way grounding should be done (only a minimum recommended level). What works great with one type of soil and normal storm profile may not work so well with another soil type and normal storm profile. For example, an install in Florida (where lightning storms are common and soil is sandy and a high salt content) you might get by with a few longer rods while an install in a high plains desert area (with few storms, but poor soil conductivity and shallow soil levels) you may need a large number of rather short ground rods with a buried mesh ground screen.