Antenna mast Iron Pipe, EMT, Galvanized....
I like the antenna mast design from WV7U:
WV7U Tilt-Over Antenna Mast
The only problem is, nobody near me stocks 20' section of either galvanized or black iron pipe. All I want to string up is a thin dipole for 40m. I'm wondering if I can get away with using EMT conduit for this or if that would be way too flimsy?
Just "plain" e.m.t. wouldn't be strong enough. Also, at least for decades, the "standard" length of pipe was 21 feet! Why? I have no idea. My mother's father and her eldest brother were both plumbers and when I was in elementary school and they needed a "gofer" guess who got to do the work!
You might be able to find some of the heavy duty galvanized "top rail" for chain link fences that would work. I don't know about the "top rail" used for residential chain link fences since that is relatively light, but, that which is used for industrial purposes is pretty strong.
I almost forgot: You can do the same thing with 2x4 pieces of lumber. The older ARRL Antenna Manuals had exactly the same "setup" as 7U except that the system was made of wood.
It might be okay if you guy it once it's vertical; but EMT alone, with the pull of a 40m dipole hanging off one side of it, sounds like a recipe for eventual failure.
If you are only supporting one end of a dipole, a single "back guy" heading the opposite direction from the dipole might be enough; or if you use this as the center support for an inverted vee, the load will be balanced on the mast and it would probably be okay by itself, provided the tension on both sides of the inverted vee are pretty equal.
The UPS shipping limit is 8 feet.
Why not use heavy-wall aluminum ?
You can get that in 20 foot sections from a local California aluminum distributor !
Penninger Radio carries long aluminum tubing lengths.
2" x 1/8" wall starter tube.
Can be mounted to a post in the ground or on a wall.
Mount plate is 3/8" x 3 1/2" x 20"
8 3/8" mounting holes
Shipping weight is 10 lbs.
Mount to a 4" x 4” pressure treated post with 4 to 8 - 3/8” bolts.
(For up to 30’ of mast.)
Surely you must have scaffolding erectors in your town who use steel tubes, 21 feet long ! to erect scaffolding for builders, roofers, maintenance work. Often they will sell steel tubing, especially as the house bulding market has gone down the pan. Look in your phone book there must be one nearby, and buy some steel 2" tube from them.
The cost of pipe is otrageous! Was it always this expensive? I'm being quoted about $85 for 21' of 1-1/2 black iron.
Lowes carries black pipe.
Another problem with EMT is that standard methods of connecting two pieces together is not strong enough for this purpose. IMT conduit, 2 10' with the supplied couple could work.
You would likely be better off looking around the neighborhood for a tower that someone no longer uses. Usually lots of unused towers around. A tube tower in decent shape would do the trick and likely save you some money. If you can put it up.
Originally Posted by KI6LNG
$85 does sound steep but then, it could be because black iron is meant for gas service. I use hot-dipped galvanized water pipe. The ends of my 80m cage inverted vee are each supported with two 10' sections of 1-1/2". Rigid electrical conduit is the same, except that it doesn't have a seam inside and costs a bit more. I use electrical conduit couplings, as they engage more of the male pipe threads than couplings meant for water (or gas) pipe. If you're nervous about the strength of the joint, you can weld them in place. You definitely don't want to use EMT or IMC, as they have substantially thinner walls than Schedule 40 water pipe or rigid electrical conduit. Lowes shows a store in Vacaville and there's a Home DePot in Fairfield. Thinking outside of the box (store), you may also have a plumbing or industrial metal supplier nearby. They'll have longer lengths.
Originally Posted by KI6LNG
I built a 35' tilt-up mast to support one end of a 40m dipole. I used a 10' section of 2-1/2" schedule 40 galvanized as a base (3' in concrete). The tilt-up assembly is 3 sections of 2" aluminum schedule 40 (6061 alloy), pivoted on the iron pipe 5' above ground. It does bow noticeably but has survived a couple of years of Pac NW storms.