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Grounding

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#1
I have a question about grounding a base antenna mast. The installer for my Dish TV, mounted on a 4 ft pole, grounded the double coax to the steel frame under my mobile home. The installer for my satellite dish, mounted on a 6 ft pole, did the same. I plan to put up a 12 ft pole for my base antenna. Can I ground this pole the same way to the steel frame. For so far I know this steel frame is grounded to the power line which comes in my mobile home. The power line is grounded to a 8 ft bar 20 ft away from my home where the power line comes in from the power company. Please advice.
 

thinder

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Silverdale WA
#2
Yes,The frame of mobile home must be grounded to the common neutral of your triplex incoming power line so it would create an acceptable earth ground.However no guarantee that it would be a good RF ground. If you have any doubt about ground take an ohm meter ,touch one lead to the the round ground hole with a 3 prong extension cord and the other to the frame and you should get about a 4 ohm short. Hope this helps
 
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#4
And the metal frame AND neutral are connected to a ground rod????

That is where a ground for your antenna mast should go DIRECTLY to.
 
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#6
Ideally (NEC/National Electrical Code Articles 250 and 810) your antenna would have its own grounding electrode and this would be bonded to the building or trailer grounding system. If you're at low risk for lightning strikes, you'll probably be okay with just bonding the mast to the trailer frame.
 
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Lisbon MD
#7
All good advice here. The only thing I can add to it is that for lighting avoidance, I suggest running a SECOND ground wire from the antenna STRAIGHT DOWN to a ground rod. Bond (connect) that ground rod to the other ground system with heavy (I'm envisioning at least #10 or larger) ground wire.

Any bends in the ground wire will incur extra inductance. The straighter that ground wire is, the more likely that most of the lightning charge will follow it.

This is extra insurance. Do note, I've seen instances where a direct lightning strike hit (not far from where you live) and that extra ground wire was missing. It destroyed a lot of equipment. Other places with that ground wire have taken similar direct hits and there wasn't even significant damage.
 
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#8
Grounding is like an old wife's tale. If you ask 3 people what the correct way of doing it are, you will get between 5 and 8 answers.

Maybe the better thing to do is to actually do some homework on the subject. There are numerous threads about grounding on the Internet. The strange thing is they all don't say the same thing.

So lets take a step back and try looking at this from a different prospective. First as the question about is the trailer frame, is it actually grounded. Look around and see if you can find any ground wire from the frame going to a ground rod. If you do find a ground wire, does it have the paint removed from under the ground lug? Was there an anti oxidant grease applied between the frame and the ground lug? Does the ground lug have two holes and both have bolts through them? Reason for the 2 hole lug is that with only one hole and one bolt, they can work loose with it being yanked on or hit by a lawn mower.

Now that you have found or not found the trailer frame grounded or not, lets talk about the "Telecommunications" antenna you brought up the question on in the first place. In the NEC (national Electrical Code) there is a section devoted just to telecommunications antennas. The section says something to the effect that you can have a separate grounding of the telecommunications system and then connect that to the electrical ground. In short, the grounding ring ground around the communications shelter and the ground ring around the antenna system can be tied to the electrical ground. This ground ring is made up of multiple ground rods space twice their length around the ring. All the connections are exothermically welded.

To make it simple, it is a good practice to add a ground rod to the base of any antenna structure, and use surge protection on the antenna transmission line. I would not use anything smaller than a #10 wire. The telecommunication companies use a #2 solid wire for their outside grounds.

The size of the ground rod will depend on your soil. If you have good soil with low resistance, a single 8 foot ground rod should be enough. If you have sandy soil, it may take 20 or more feet in length to get a low resistance ground. It may even require multiple ground rods to get a low resistance ground. The goal that the telecommunications companies look for is a ground that is 5 Ohms or less. If you have to use multiple ground rods, make sure you space them at least twice their length apart.

One other place you could check is your home owners insurance company. Many times the insurance company will have their own guide lines that you should be following. If you have a strike and damage is done, the insurance company might just say something to the effect that you have not followed our guide lines and we are not paying the claim.

I have surge protectors on all my coax cables coming into my radio room. They are all connected to various ground rods as they don't all enter the workshop at the same location.
 
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