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Metal roof question

Discussion in 'CB Antennas' started by okie, Oct 17, 2019.

  1. okie

    okie Member

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    I am putting up my first beam this week and was going to mount it above a piece 30' of 2-7/8 oilfield pipe.

    With the pipe and a piece of mast, the bottom of the vertical elements will be only about 7 or 8' above my metal roof. Will the beam being that close to a metal roof cause interference? Btw, the beam is a Maco Y Quad.


     

  2. Unit 75

    Unit 75 Sweet Home Alabama

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    It probably will. Being too close to the metal roof is going to mess with your antennas radiation pattern. If it isn't too much trouble try it and see what your match is like on both horizontal and vertical polarities. I think your horizontal SWR will be high.
     
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  3. okie

    okie Member

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    Unit 75, thanks. What do you think is the minimum clearance I need? I have several pieces of 5' (1.5") Rohn mast pipe but I dont want to be too flimsy.
     
  4. Unit 75

    Unit 75 Sweet Home Alabama

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    I ran the same antenna mounted on a pole/mast that ran upside the back of the house. I would say that the antenna was probably 12-15 feet above the metal roof and I had issues on the horizontal but the vertical was ok. I ended up buying a 45 foot tower, which cured my problem. You do not want to run a pole that high as it will bend in the wind. Every install is different due to location and surroundings. I would say the higher the better is the best advice I can give you at the moment. The only way to know for sure is to try it out. Going up that extra 10 feet (using the tower) cured my problem.
     
  5. 357magnum

    357magnum Sr. Member

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    I wanted to put a steel roof on my house . I'm also installing a Sirio 27-4 Beam . I only wanted a short mast coming out of the rotor , I asked around & told The Wife ... Conventional Shingles it is !:LOL:
     
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  6. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    :whistle:If you do it right the metal roof will be the ground plane.
     
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  7. 357magnum

    357magnum Sr. Member

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    Shade , Wouldn't work for me ( I don't think ) as I was going to mount mine on the end of my house . Depending on direction the amount of beam exposed to the metal roof would vary . I guess if you used a Tri-pod & metal was completely under beam , you might have a shot ? I just don't want to take any chance & don't feel like putting up a tower which is the way it should be done .;):confused: IMO
     
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  8. dledinger

    dledinger WDX995 / 2NC995

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    You have to have a magmount beam if you want it to work right.
     
  9. 357magnum

    357magnum Sr. Member

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    dled ,(y)o_O:ROFLMAO:
     
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  10. Jay Mojave

    Jay Mojave Well-Known Member

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    Hello okie: The Y quad beam antenna might be slightly effected by the metal roof. If the antenna could be higher that would be better.

    Be advised metal roofs mostly are not grounded, that means they will pick up noise, static and the such. Especially during a lightning storm.

    If the antenna mast is grounded and the upper part connected to the metal roof these noise and static energies will use the mast to flow these noises and static to ground causing a very noisy receive. And drive ya nutzoid trying to fix it. But not all metal roofs will do this. The metal roof is constructed to NOT leak and NOT fly off in heavy winds. Its NOT designed to NOT give off Radio Interference. And some do.

    I would give that antenna install a try at least so maybe if you get it higher in the further you can compare it to being closer to the metal roof. Good luck. Please let us know how it all turns out.

    Jay in the Great Mojave Desert
     
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  11. Marconi

    Marconi Usually if I can hear em' I can talk to em'.

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    Hello Okie. I have a model of the Maco 103C antenna that I setup Vertical.

    I also have a modeling object that I made, a metal pitched roof 17'H x 30'L x 38'W.

    I set this vertical M103C model on a mast connected to the ground and 2' feet from the building at its peak. The bottom of the vertical elements are about 7.5' feet above the 17' foot roof peak.

    Note: these models do not necessarily represent what will happen at your location.

    I think Jay gave you a reasonable expectation in answer to your question and I see the models below in support of his suggestions.

    Models in the PDF file below.

    1. shows the starting model, a vertical Maco 103C with no metal building.
    2. shows the beam 2' feet from the metal roof of a building and pointing North over the roof top.
    3. shows the same view as #2 with the beam pointing South away from the metal roof.
    4. shows the beam rotated 90* degrees pointing to the East.

    As I rotated the antenna in these three directions I noticed the feed point match changing. So, I tweaked each model a bit to make for an improved match. On rotating your antenna in this situation...you might expect the match to vary as you rotate.

    I will also do the horizontal version later just as Unit 75 suggested, and see what modeling might suggest there as well. Again, I think Jay is right.

    Okie, keep us posted on your progress.
     

    Attached Files:

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  12. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    The best way is to mount it is on a tripod in the center of the roof. It will affect your radiation pattern to some degree. But the swr should be lower than trying mounting off of the side.
     
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  13. okie

    okie Member

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    Thank you all for the help and the pdf file. I ended up breaking the antenna but not beyond repair. I had a 30' joint of 2-3/8" oilfield pipe on a tilt base with a couple of pieces of Rohn 5' mast. About 40' total. Swrs were 2.0+ but made good skip contacts and talked to several base stations 45 or so miles away. Layed it over and added 2 more pieces of Rohn mast pipe and should not have. The mast broke on the way up and the Y quad was bent badly on the rejection side. Ordered a 103c from Copper but am going to try and repair this or maybe use the parts to build a vertical or something.
    Going to put the 103c up on the piece of 30' oilfield pipe with one 5' Rohn mast and call it good.
    Again, thank you for all the advice. Was working well until I started trying to go taller and taller. .... live and learn
     

    Attached Files:

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  14. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    That Rohn pipe as well as the top rail fence pipe seem too thin. I did a tilt over with 10 foot sections of water pipe. I would love to have used a 30ft section like you did. Here is a link to the Vector 4k install that I did with the tilt over mast.

    https://www.worldwidedx.com/threads/sirio-new-vector-4000-install.226677/
     
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  15. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Is your Oil field pipe drill string or completion tubing?
     

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