Grounding an Antenna Mast

[Paintedcow]

Last year I put up a TV antenna mast. I didn't want to screw it to the roof, so I ran three 10 foot lengths of 1 1/4 EMT conduit up the side of the house, and bracketed it to the side of the house. I buried the bottom about 10 inches in the soil. That got the top of that mast about

8 foot above the roof. Which is where the antenna sits. (I had a machine shop make me some sturdy splicers to connect the EMT conduit sections together, because those connectors sold for EMT are too weak for my use). There are also a few guy wires to secure this mase in case of wind. Those are connected to the side of the house.

Anyhow, I never really grounded this mast, and think I should. That 10" buried into the soil is not really a suitable ground. One of the ground rods for my house's electrical system is only about 8 feet from the mast, so I can run a wire to that. My problem is how to connect that wire to the conduit. The commercial ground rod clamps are not big enough to go around that conduit. I thought about clamping it with a stainless steel hose clamp, but that's not the best connection. A muffler clamp os my other thought, but the way they rust, I'd almost think a S.S. hose clamp would be the better if the two. I suppose I could also drill a hole in the conduit and put a bolt thru is, but I'd prefer to not weaken the conduit with a hole.

Maybe some of you will have a better idea about what to use to clamp it. I'll probably use #8 or #10 bare copper wire for this, or insulated, depending on what I have laying around.

Ideally, I think a Stainless Steel muffler type clamp would be best, if I could find such a thing.

[Retired]

Try McMaster-Carr at

They have SS muffler clamps

[Micky]

That's good to know, but DD, why would these be better than stainless steel hose clamps? I assume you mean -- or at least I mean -- the kind with a worm gear. One of them would make more contact with the conduit than one of these muffler clamps would.

[gfretwell]

They may not have them at your Home Depot but they make pipe clamps that go up into 6-10" pipe. One for 1.125" EMT should be at any electrical supply. It will be a split type thing with 2 SS bolts holding it together.

[Unquestionably Confused]

I doubt that boring a hole through the EMT to connect the ground is going to be a problem. Think it out: You're at the bottom of the mast, you've bracketed and guyed the mast along the entire run, what forces other than gravity/weight of the mast are likely to be applied to the area where you will drill?

Your more immediate problem is likely to be rust at the base. Did you leave the end open and sitting on a bed of gravel? Where is the water, condensate that will build up and pool at the bottom of the mast going to go?

I had a freestanding, 40' Rohn tower for my TV antenna and rotor. The base section was set in 24" x 24" x 48" poured concrete foundation with

3/4" steel rebar driven outward of the hole before the concrete was poured. Note that the Rohn tower is heavily galvanized and the base section, IIRC was 36" - 42" in length. It took about 35 years but eventually it rusted out at the base (where the first section connects to the base piece and I came home one day to find it laying across the driveway. I didn't leave a drain for the base.

Fortunately there was no damage other than to the antenna which had seen better days anyway. As luck would have it, I found that regular galvanized pipe made a very nice reinforcing insert when slipped down inside the tower pieces. The galvanized pipe was placed and extended about 18" above the base. That setup and a friend with an aerial bucket and I was back in business. If anything, the tower is more secure than before. Yeah, I didn't do anything about the drainage issue; it will rust out again but not in my lifetime and I added a heavy steel standoff bracket (mfg by Rohn) which is attached to the studs in the sidewall of my house.

[Eagle]

[e-mail] laid this down on his screen :

Is soldering a possible solution? What material is the conduit made of?

[Ralph Mowery]

Am I understanding the rebar correctly ? All of the rebar should be enclosed in the concrete by about 2 inches. If not, when it rusts , it expands and cracks the concrete.

[Ralph Mowery]

Maks sure the copper wire is not agaisnt the EMT. It should be used with a clamp that has a seperate screw for the wire. Copper and stainless is ok.

[Unquestionably Confused]

I think you are.

This was a "belts and suspenders" move on my part. The concrete alone was sufficient and there's been no evidences whatsoever of deterioration there. Think of the 14x24x48 poured base with LEGS. I think I also pounded in a couple of metal fence T-posts as well. Even with some fairly stiff wind storms here, even without the relatively new bracket to the house (remember, that tower was unguyed and unbracketed until the rust out) that sucker was and remains perfectly plumb.

[Unquestionably Confused]

[snip]

In my installation, I drove an 8' or 10' ground rod adjacent to the tower base and then used a pre-terminated length of automotive battery cable between the ground rod and the tower, fastening the cable to the tower through one of the leg's two bolts.

[David L. Martel]

The large cables used for grounding may be aluminum. Steel and aluminum may not go together well. Copper is expensive but may be a better choice. Don't forget a lightening arrestor for the antenna cable

Dave M.

[gfretwell]

Aluminum is prohibited as a ground rod conductor.

[Paintedcow]

I was thinking about that. I think I'll use a S.S. U-bolt and clamp half of a standard two piece brass ground rod clamp, and clamp that piece to the mast. Those have a screw on them. Brass is probably better than copper against steel. (Like brass valves in galvanized pipe)

I'm glad someone mentioned a weep hole for water. I suppose some water can still get in the pipe at the pieces that connect the pipe sections, even though I covered the top of the pipe with duct tape before I raised it. Maybe I should drill at least a 1/8" hole right at ground level, even if the water can soak into the soil.

[trader_4]

What was wrong with Gfre's idea, to use a ground clamp for a water pipe, like is used to ground the service? Seems it's ideally suited to me.

[Jon Danniken]

It's EMT, so galvanized steel.

Jon

[makolber]

Do you mean aluminum is prohibited as the ground rod itself or is it also prohibited as the ground wire connected to the ground rod.

I don't see aluminum ground rods but I do see a lot of aluminum ground __wire___.

Mark

[Scott Lurndal]

NEC:

access is free, requires registration.

[Eagle]

So much for soldering.

[gfretwell]

You shouldn't see it going to a rod.

250.64(A) ... ... Where used outside, aluminum or copper-clad aluminum grounding conductors shall not be terminated within 450 mm (18 in.) of the earth.

[Paintedcow]

I'm not sure what those look like, but if I can find one that will fit a

1 1/4 inch pipe, that seems like it would be ideal.

The local hardware store dont have them, but maybe one of the big box stores does. But I dont live near any of them. About once a month I will make the 1.5 hour drive (each way).