35' PVC Antenna Mast/Tower Ideas

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KD8EZP, Feb 22, 2011.

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  1. KD8EZP

    KD8EZP Ham Member

    Does anybody have any thoughts on building a 35' mast useing 4" PVC pipe?

    I was thinking of mounting the 10' x 4" pvc between two wooden 8' 4x4's that would be half mounted in a concrete base. The 4" pipe would be fixed with two bolts to that when one bolt is removed the mast could swing down. A portion of the bottom of the 4" pipe could be filled with concrete for ballast. On top of the 4" pipe would be 10' x 3" PVC pipe and on top of that 10'x 2", then on top of that 10' x 1.5". Of course they would sleeve into one another for a certain amount and acheiving aproximately 35'.

    Does this sound feasable?

    Dave
     
  2. W4AFB

    W4AFB Guest

    A 40ft Rohn push up pole would be a better bet and safer.
     
  3. N3JPB

    N3JPB Ham Member

    Dave,

    What you are describing is actually quite a popular method of installing a vertical antenna, as an example:

    http://verticaldipoles.tripod.com/MountingSystems.html

    What you are describing gives you a stable platform for housing your antenna. Now, what are you planning to put into this "empty shell"? Your radiating elements could be made of wire or made of copper pipe. Are you going to make the antenna a dipole (as in the cited example - then the center feed line must be perpendicular to the radiating elements) or as an end fed radiator with a field of buried radials? Are you planning to use a choke/balun?

    Good luck with your project.

    Regards, John (N3JPB)
     
  4. G0GQK

    G0GQK Ham Member

    What you have to consider is the weight of plastic tubing when it is moved from a horizontal position to a vertical. The idea is sound but the plastic material could be a problem as there is very little rigidity. What do you intend to do with this vertical tube ? Support a dipole or as a vertical radiator ?

    The usual method is to taper a vertical to lessen the weight as it is raised, you would be surprised at how heavy things become. If it is to be a vertical why not consider an extending fibreglass pole and extend the lower section by the addition of timber or aluminium tubing which will fit over the outside of the fibreglass.

    Or use a smaller diameter plastic tube and strengthen it by inserting wood.

    G0GQK
     
  5. K9STH

    K9STH Ham Member

    PVC is NOT rated as a structural material. When the weather gets cold, which I do believe it does in Michigan ( :rolleyes: ), and the winter wind blows, there is a VERY good chance of the PVC failing and down comes the antenna.

    Glen, K9STH
     
  6. WX7G

    WX7G Ham Member

    PVC is a terrible structural material. Wood on the other hand is very nice. And aluminum is even better.
     
  7. N8WH

    N8WH Ham Member

    sIR.i HAVE A 37FT. PVC MAST THAT HAS BEEN UP FOR 6 YEARS. i USED SCHEDULE 80 PVC PIPE AND REDUCING BELL TYPE COUPLINGS(HEAVY ON THE GLUE) ALSO I INSTALLED FOUR NYLON ROPE GUYS APROX 18 INCHES BELOW THE ANTENNA. I USED 4" TO 3" TO 2" TO 1.5". THE BELL TYPE REDUCING COUPLINGS ARE MUCH BETTER THAN THE STRAIGHT COUPLINGS.

    BILL
     
  8. WA4OTD

    WA4OTD XML Subscriber

    You can get a kit of 12 four foot fiberglass poles for about $20 that are meant to be an antenna support. They do require guy wires. You can get these on ebay or at most hamfests.
     
  9. KD8EZP

    KD8EZP Ham Member

    Wow, I didn't expect so many helpfull comments. The mast would be used to support an OCF Dipole. Also perhaps a 2 meter vert (later). Well from the comments it sounds like it might be worth having a go. The scedule 80 (or 120) pipe would be best. I'm not sure how available that is compared to just running down to lowes or something. Thanks all.

    N8WH - Where did you get the 'Bell Type Reducing Couplings'?.
     
  10. W4AFB

    W4AFB Guest

    Find a push up pole. You'll be much happier and have a safer structure.
     
  11. W0BTU

    W0BTU Ham Member

    Like the 40' A-frame made out of 2x2 wood in all the ARRL antenna books? They must work.
     
  12. Vanillaxa

    Vanillaxa New Member

    Thank you very much! I'll give it a try.

    Cheers





    ------------------------------------------------------
    typing service
     
  13. W6UX

    W6UX Premium Subscriber

    If you haven't seen what Max Gain Systems offers, I recommend you check them out: www.mgs4u.com. I've got the 50' telescoping fiberglass mast. It is solid in high winds. Needs to be guyed of course. My dipole is set at a height of 43 feet. 1/8" thick material so it's super rigid.

    Jeff W6UX
     
  14. WX7G

    WX7G Ham Member

    I have built many of the ARRL Handbook A-frame towers. Up to 40' using 2 x 4 lumber for Yagis, 2 x 2 lumber for wire antennas, and 1 x 2 lumber for lightweight wire antennas. One of the nice things about the 1 x 2 A-frame is that if it does fall down it isn't going to damage anything. And at $1 per 8' length of lumber the paint costs more than the wood.
     
  15. W0BTU

    W0BTU Ham Member

    I wonder how high you could go with 2x4 -- perhaps with 2x6 at the bottom -- for a wire antenna?
     
  16. K6OK

    K6OK Ham Member

    Modulus of elasticity of PVC pipe = 360,000 psi
    Modulus of elasticity of aluminum pipe = 10,000,000 psi

    ... which means PVC pipe is 27 times more "floppy" than aluminum (assuming the same diameter and wall thickness). Imagine a stiff breeze that makes the aluminum mast move one inch at the top; the PVC mast will bend by more than 2 feet. You'll be surprised how floppy the PVC is. It's like a noodle. With guy wires or cords it can be made to work, but eventually you'll wish you had steel, aluminum or fiberglass instead. 73 Jim
     
  17. KB0YYO

    KB0YYO Subscriber

    my experience only.
    I have used PVC and it looks good for a while. The sun tends to warm it up and it begins to show warping. After while it looks crappy. Like a not so stiff worm .
    Sure PVC is cheap and it does tend to make cheap temp antennas that usually have a short life span.
    Most importantly is that "you gotta do what you gotta do." to get on the air.

    As for the mentioned Fiberglas poles from EBAY. I bought 3 of them. They do not telescope but are Ex Military and in the green carry bag with all the military markings. Buy it now $7.50 and $24.00 for shipping NY to KS USPS.
    12 poles @ 48" long I thought it was a decent deal.
    Field day, vert antenna, support for long wire, many potential uses.
    let us know what you do and how it worked out for ya.
     
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