Advice sought for installing a 2" WISP antenna in an existing 3.5" cut-off mast hole

Any ideas for installing a new antenna mast into an old antenna hole?

OLD: I have an old 3.5 inch ID steel tube sunk in 30 inches of concrete. I'm guessing this was an old satellite dish cut off flush with the surface (unfortunately). No threads but the steel is 1/4 thick (or so) and in good shape and it goes down to 30 inches in the concrete.

NEW: I simply need an antenna mast of about 12 feet high for a new WISP 802.11 antenna & radio setup. Winds can be high at times. Soil is rocky clay. I prefer NOT to have guy wires as the kids play in that area.

IDEA: The best idea is to find a way to shove a 3.5 inch OD pipe 30 inches into the existing pipe and then thread successively smaller pipe down to 2 inches for the final mast. But I can't find a source for 3.5 inch OD pipe that has threads on at least one end so that I can put a reducer on that end.

COMPROMISE: I can easily find 2 inch and 1 1/2 inch threaded galvanized water pipe with reducer fittings and caps - but I can't find 3.5 inch water pipe and associated fittings for the bottom portion of the mast.

TWO QUESTIONS: Q1: If I stick with the original idea, where would I get a 3.5 inch OD pipe that has threads that can hold a reducer to more available widths?

Q2: If I go with what I have right now, how would YOU shore up the pipe but still allow easy removal for maintenance?

DETAILS: Currently it's working but physically wobbling. I remove the entire mast to service the antenna.

The mast is comprised of a five foot length of 2 inch ID threaded galvanized water pipe sitting 30 inches deep inside the existing 3.5 inch ID iron pipe cut flush at the concrete. This five foot length of water pipe sticks roughly 2 1/2 feet out of the ground where I then threaded on a reducer which couples easily to the 10 foot length of 1 1/2 inch ID threaded water pipe forming the bulk of the mast, and which is capped at the top (to prevent water from filling the pipe).

The 14 dBi planar 2.4 Ghz antenna at top is roughly pointed at the WISP access point; the Bullet M2 radio tells me it has an ACK/Distance of

55/2.6 miles respectively (I'm not sure if that's important); this radio sees a signal strength of -56 dBm (pretty good); with a transmit CCQ of 83% (just ok).

It's working - but it's not a permanent solution.

I am stuck at HOW to fix the antenna in the ground so that it won't wobble & spin (short of digging a new hole & concreting it in) yet being able to service the antenna (I have ladders but not a 12 foot high step ladder - plus the ground is sloping so it's unsafe to ladder it).

Do you have ideas how to affix the antenna mast into the old 3.5 inch ID hole while still being able to remove the entire mast for antenna service?

NOTE: In the future I'd like to add a TV antenna but that's not the primary goal.

All ideas welcome.

Reply to
Frank Wilson
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Put a clamp on the pipe about 5' off the ground Attach to outriders at an angle that are set in the ground These will give you rotational and vertical stability By loosening the clamp, you can rotate the pipe to re-orient it as needed.

As to climbing up the pipe to service it, use climbing sticks like the ones deer hunters use to go up to their stands

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climbing sticks kits can even be joined to multiply the height reached.

Reply to

Assuming you've found the 3.5" OD pipe, all you need is a way to attach your

2" mast. Threading with a reducer is one way, so the next step is find some way to put threads on your 3.5" OD pipe.

  1. Find an oil or water well supplier. They'll probably have some way to thread the sucker.

  2. Buy your own 3.5" pipe threading die (~5.00).
Reply to

Fix to the 2" OD final mast a pair of 2" ID/3.5" OD centering spacers/"donuts" near bottom and top of the 30" submerged portion of the final mast.

Insert final mast with spacers into the old 3.5" ID shaft. Easy in, easy out for maintenance.

Reply to

Try looking in the Forums at this site.

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under Search for Antenna Mounting.

Reply to

If the dimensions you give are accurate....

You could use 3" pipe (has a 3.5" OD) obtained from McMaster Carr.

You could could a full length insert (24" to 36") and then use a coupling w/ a threaded reducing bushing.


Buy a short piece of 3" SCH 80 pipe to make adapter donuts as suggested by another poster.

check out

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?page=3Dpipeandtube the dimensions given have tolerance on them and the various pipe sizes & thicknesses might need some "machining" to get a proper fix.

You could wet anchor a 2" pipe (2-3/8" OD) into the existing hole using a high strength setting compound.

Threaded pipe joints in bending situations make me nervous.

cheers Bob

Reply to

Note whatever you use as "cement", it has to set in the winter. Well unless the OP is from down under.

I run into installations in the boonies where it looks like stakes were epoxied into crevices of rock. Any idea what kind of compounds are used to do this? This is sort of the case where you don't know how to ask the right question in google. In fact one spot had threaded pipe in the rock, and I suspect they found a hole and just filled it to set the pipe rather than dig into rock.

Reply to

I'm not sure I understand this suggestion.

The existing 3.5" ID pipe is cut flush with the concrete so I can't put any clamp on that.

I guess you're suggesting I put a clamp on the five-foot length of 2" ID galvanized water pipe (which is about 2 1/2" OD). But I don't understand the 'outriders' part.

Interesting idea. I found a video of them being used. They are supposed to go around trees though, so I am not sure if they'll work on 1 1/2" ID water pipe (about 2" OD).

I think it may be time to invest in a taller 12' stepladder (which I could use for trimming trees around the antenna also).

Reply to
Frank Wilson

I'm told (by local plumbers) that I might be able to find inexpensive (about $50) yellow steel "ballard" (or "bollard") pipes at 3.5" OD:

Ballards/bollards are, I am told, the name for those removable posts that utilities put all around transformers and other vulnerable equipment in parking lots so that trucks/cars don't run them over.

I'm not sure if they're called 'ballards' or 'bollards'.

This site calls them ballards:

This one calls them bollards:

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Threading with a reducer is one way, so the next step is

Reply to
Frank Wilson

Sorry about that last post - I hit the send button too soon! I'll clarify.

Local plumbers told me to look for 'ballards' or 'bollards', which are apparently inexpensive pipe posts ($50) that are about the right diameter which are designed to be used as "dissuasive perimeter control" barrier posts around areas so that cars don't drive through them.

This site calls them "Pipe Ballards" but they only have 3" diameters:

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This site calls them "Steel Bollard Posts" & but they only have 4", 5", &

6" diameters:
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This is a bollard FAQ:

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I'm still googling for a 3.5" OD bollard/ballard post ...

Reply to
Frank Wilson

That would be about the size used for a big C-band 8ft dish. DBS dishes use smaller pipes, usually 2".

How's your stick arc welding? Jack hammer enough of the concrete from around the pipe to expose enough of the original 3.5" ID steel pipe to make an effective weld. Find an internal sleeve that's approximately the correct size. My guess is 3" steel pipe will have roughly a 3.5" OD can will make a good sleeve. You might have to do some grinding to the OD in order to get it to fit. Pound it into the original 3" pipe in the ground. Make some effort to get the pipe to be exactly vertical. It makes antenna aiming MUCH easier. Tack weld in place.

When you're done welding the stub/nipple, you'll probably need to mix a little concrete and fill in the area around the welt to prevent water accumulation. I suggest removing as much slag as possible and painting with a rust resistant paint, before applying the concrete.

At this point, you have several choices. If you use a threaded 3" steel pipe, you can attach any of an assortment of pipe fittings to extend the pipe to the desired altitude. However, I wouldn't do that.

12ft is a LONG way to go with a single steel pipe. Even with pipe fitting or pipe union, it's going to wobble. You're also looking at 7.3 lbs per foot for 3" pipe or 88 lbs of pipe.

If you don't like guy wires, you'll need to do a good stick arc welding job.

You can go to a smaller diameter pipe, but if your 2.4GHz antenna has a narrow beamwidth, you're going to have alignment stability problems, especially when the wind is blowing. For example, the common 24dBi parabolic dish antenna has about a 6 degree -3dB beamwidth, which has to be aimed within about a 3 degree range to be usable. That's not easy on top of a 12 ft pole unless it's VERY stable.

Any plumbing vendor. Ask for 3" ID 40 steel pipe. I would NOT try to pound a 12ft pipe length into the 3.5" pipe that's in the ground (unless you have a 15ft ladder and find it entertaining to use a sledge hammer on top of the ladder). Use a welded stub/nipple pipe as previously described.

Nipple sleeve welded in order to extend the original pipe above ground level. Use a pipe coupler if you want to make it strong an permanent. Use a pipe union to make it removable but not so strong. Unions are not made for this type of service. I couldn't find if it will handle the bending load. That should be researched before building.

Why do you need to lower the pipe? A 12ft step ladder should be sufficient.

Ubiquiti products are good. A 14dBi panel antenna means it's probably a sector antenna (kinda rectangular looking), which will have about a

15 degree vertical beamwidth and about a 60 degree horizontal beamwidth. That's not very critical or difficult to aim. If your pipe is really vertical, and you have line of sight, you could probably preset the antenna and not worry about tweaking it once erected.

As previously mentioned, chip away some of the concrete. Pound in a

3" pipe stub/nipple. Arc weld. Add mast.

Yep. Get a 12ft ladder. Without guys, the pipe will not support your weight so forget about slithering up the pipe using foot pegs or an ascender. If this bothers you, I suggest you forget about the pipe, and switch to a 10 ft section of Rohn 25 tower. Weld the base plate to what's left of the 3.5" pipe in the ground. You will also need to drill into the concrete to secure the base plate mounting bolts.

Hmmm... with small brats climbing everything in sight, maybe not...

You'll have a problem trying to get the 1.625" U bolts that come with the typical TV antenna to fit the pipe.

Good luck. Try not to kill yourself doing this.

Reply to
Jeff Liebermann

Two part catalytic mixes will set at any temperature.

"Anchor bolt grout", usually a two part epoxy. You'll find it at any hardware store that sells to builders:

Look for Loctite 1108757. You won't like the price.

I carry several star drills in my install kit. I hate pounding holes by hand into existing concrete pads, but it works. I've never tried it on rocks.

Reply to
Jeff Liebermann

I hear they might still have some spare stuff left over from Boston's Big Dig....

Reply to
danny burstein

How big is the pad. You might drill 3-4 holes and make another mount, using cement bolts. Probably need a welded plate.


Reply to

Hi Jeff,

This is Soda Springs unconsolidated rocky stuff so I need the 3.5" ID pipe set in concrete! :)

My WISP just now suggested I use something called "unistruts" to secure the 2" ID water pipe (2-3/8" OD) into the 3.5" ID hole.

Do you have any experience with unistruts?

Reply to
Frank Wilson

Hi Jeff,

This is Soda Springs unconsolidated rocky stuff so I need the 3.5" ID pipe set in concrete! :)

My WISP just now suggested I use something called "unistruts" to secure the 2" ID water pipe (2-3/8" OD) into the 3.5" ID hole.

Do you have any experience with unistruts?

Reply to
Frank Wilson

If you are going to weld, and rather than use guy ropes, you could brace the pole effectively by using standoff tabs and full length reinforcing rod in four vertical positions.

Reply to
Dr Who

Look for an "orchard ladder". It has a pipe stabilizer on the other side to keep from bending the mast with your weight.

Tilt over masts and towers are available commercially from the various tower suppliers. You will not like the price. You can also make your own. Look at the photos for ideas:

If you change your mind about the guy wires, it can be done quite easily with a base mounted hinge point. You also won't need a heavy weight mast as a simple 10+5ft, 1 5/8" dia, will suffice if you keep the weight down. For example, no rotator. If wind loading is a problem, go to an antenna with a smaller wind load, such as a 19dbi or

24dBi barbeque grill parabolic dish. As for the kids, you might try installing springs on the guys. When they crash into the guy wires, the damage will be minimal.

Ok, get a heavy duty ladder and work with a mattress under the ladder.

That will work, but ever fitting will weaken the mast and possibly make it wobble. For mounting the TV antenna, you can build some manner of adapter or creative mounting contrivance. I have a mess of these for the occasion (except mine are 1/4" aluminum and much larger). Make your own to fit.

That you could have figured out yourself.

1.315 OD which is less than 1.625 for the TV mast. Yes, it will fit.
Reply to
Jeff Liebermann

I think the gray stuff is what they used. Thanks.

The place where I saw this pipe and anchors was listed to have a seismic sensor in the general area. I suspect the antenna was mounted with the pipe in the ground (actually rocky hillside) and guy wire eyelets. You wouldn't even notice this spot if you weren't hiking up the hill. My guess is it would have been too much work to take it out.

Reply to
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