Antenna mast Iron Pipe, EMT, Galvanized....

Discussion in 'General Technical Questions and Answers' started by KI6LNG, Dec 20, 2009.

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  1. KI6LNG

    KI6LNG XML Subscriber

    Hi everyone,

    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?
     
  2. K9STH

    K9STH Ham Member

    LNG:

    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.

    Glen, K9STH
     
  3. WB2WIK

    WB2WIK Premium Subscriber

    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.
     
  4. W9GB

    W9GB Ham Member

    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.
    http://www.penningerradio.com/gallery.asp?id=14&cc=

    TJ-200
    Tipper Junior.
    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.
    $ 139.95
    http://www.penningerradio.com/gallery.asp?id=3&cc=
    Mount to a 4" x 4” pressure treated post with 4 to 8 - 3/8” bolts.
    (For up to 30’ of mast.)
     
  5. G0GQK

    G0GQK Ham Member

    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.

    G0GQK
     
  6. KI6LNG

    KI6LNG XML Subscriber

    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.
     
  7. KA9MOT

    KA9MOT Ham Member

    Lowes carries black pipe.
     
  8. NI3S

    NI3S Ham Member

    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.
     
  9. VE3FMC

    VE3FMC XML Subscriber

    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.
     
  10. WA7PRC

    WA7PRC Ham Member

    $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.

    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.

    vy 73,
    Bryan WA7PRC
     
  11. KC4RAN

    KC4RAN Ham Member

    Just don't weld galvanized metal. People die that way.
     
  12. KB7IIE

    KB7IIE Ham Member

    Antenna Mast Pipe Alternatives

    Consider the 4' fiberglass pole sections used by the US Military and are routinely found as surplus on the market. The batch of 12 that I purchased was fairly inexpensive, very well made and incredibly strong in the typical NW wind storms. Several aftermarket supply's also offer aluminum and composite guy ring supports to slip onto any section you want to tie down. They are 1 1/2 inches OD some are in Army green, others are in camouflage.

    If you are unable to find them in your location, search for them on eBay and go from there.
     
  13. KJ4QCV

    KJ4QCV Ham Member

    how about 2 10' sections from lowes, home depot, wherever have them thread the ends and use a coupler.
     
  14. K9KJM

    K9KJM Ham Member

    The 21 foot length sections of nice galvanized schedule water pipe are as close as your local full service PLUMBER. (Most of them really know how to charge however...)
    You MIGHT be able to get some good used if you can find a local full service plumbing shop who replaces deep well pump pipe. (Most new replacement pipe is now plastic, But many times they pull out the 21 foot sections of galvanized pipe, And the sections near the top of the well are usually in good shape.) Doesnt cost any more to ask. Also check with your local scrap/salvage type yards.

    Most home supply type stores only have the 10 foot length pipes, And if you use a coupler, You do reduce the overall strength a lot.
     
  15. AK4MP

    AK4MP SR. DX DATABASE MANAGER

    Keep the info coming folks. I'm thinking about one of these applications
    for use when I get my 40' tower up. Need something thick walled for 4 beams and a verticle antenna to sit in a Ham IV rotor
     
  16. AC0YW

    AC0YW Ham Member

    http://www.mgs4u.com/index.html Might have something you could adapt to your support needs, the material is VERY high quality and quite strong. In don't think you would want to try a rotor on a single member support system though due to twist forces. The material at the link will work for a wire though.
     
    Last edited: Dec 21, 2009
  17. WA4VBC

    WA4VBC Ham Member

    You might try the local salvage yard, as they often have pipe of various sizes and cheaper than new. I have a nice section of 1-1/2" stainless steel pipe I picked up from one that I plan to make an antenna mounting bracket from.
     
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