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need advice on how to properly install large boom antenna on roof tower

Discussion in 'Amateur Radio Antennas' started by Maniac373, Jun 7, 2009.

  1. Maniac373

    Maniac373 Base Station Extrordinare

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    First let me say I am taking my tech exam this coming Saturday (1 week from today).

    I have decided that I want to install a glen martin RT-936 (9 foot tall) roof top tower on my 2 story house. I am going to use a T2X tail twister rotor, a 24 foot long aluminum pipe (2" outside diameter / 1/2" wall / 1" inside diameter) for mast.

    I am putting up a large 40 foot boom beam antenna, with an omnidirectional antenna above it. I have the instructions on how to reinforce the roof-- so that wont be the problem-- I just need to know the SAFEST way to install the beam up on the mast-- I can get the roof tower mounted, I can get the mast mounted, I can even get the Omnidirectional antenna mounted on the mast... But I am scratching my head on how to get the beam on the mast once the mast is mounted in the rotor, which will be nested inside the roof top tower.


    I asked a friend, and he said I should try to get a truck with a cherry picker/ lift bucket, and install the beam that way.

    ????

    suggestions are welcome.

    Thanks

    Charlie


     
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  2. ajm1571

    ajm1571 Active Member

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    safest way would probably be to use a bucket truck.
    just my .02
     
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  3. W9WD

    W9WD Guest

    Yep
    Bucket truck.

    You'd be surprised how fast the height gets scary.

    I think I would build the whole mast/antenna/guys/coax on the ground and then use the bucket truck to lift the whole contraption to the roof and attach it.


    Good luck with your test
     
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  4. Wire Weasel

    Wire Weasel Senior Moment

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    Hi Maniac,

    The 24' mast you're suggesting sounds long. Does it really need to be that long? I know you want "the higher the better", but that will only serve for your vertical. The beam is for DX'ing and the extra height won't make any difference there.

    You're going to be a Tech and am getting a beam with a 40' boom? Is that just for 10 meters? That's going to be the biggest 10 meter beam in the world. Sounds like overkill to me.

    This rig is going to be a huge wind/weight load. It will not support itself at this length and you'll have to use guy wires.

    I would put this monster beam on only 5 feet of mast and you'll probably need a thrust bearing unit above the rotor to support the vertical side-to-side motion. You can install the beam on the mast, and then stick it in the rotor all at once with just the 3 guys picking it up. Put the vertical somewhere else to get it higher, or live with it on the tower at the reduced height.

    It doesn't matter how large or heavy duty a mast pipe is, you just don't see long masts supporting large beams. It's not done. It's too unwieldy. Most hams would put a a regular tower, use a thrust bearing above rotor, and probably like a short 5 foot mast for a beam this size.


    If you get it up just as you want, oh do come back and post us some pics fer sure.

    good luck
     
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    Last edited: Jun 7, 2009
  5. Maniac373

    Maniac373 Base Station Extrordinare

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    Im sorry I wasn't clear on this-- OOPS!

    The beam will only be 5 feet higher than the roof mounted tower (Glen Martin RT-936/9 feet tall)-- I will be using a T2X tailtwister rotor, and a Jogunn GS-065 heavy duty thrust bearing. The omnidirectional antenna will be mounted on the top of the 24 foot mast. The omnidirectional antenna has radials coming out at a downward angle-- I need the radials to have a good distance between the omni antennas radials and the boom on the horizontal beam. Thats the reason for the 24 foot long mast.

    here is a pic of my omnidirectional antenna. (please notice where the mast attaches)
    [​IMG]

    Charlie
     
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  6. Wire Weasel

    Wire Weasel Senior Moment

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    Same problem Charlie. A 24' mast ain't gonna hold itself up + the vetical on top of it. You'll need guy wires under the vertical to hold the thing up. The guy wire connection disk will have to be able to rotate, and you'll have to be able to tie the guy wires off at points that won't interfere with the big beam. There doesn't have to be that much separation between the vertical's radials and the beam. This could be additionally great shortened if you went with an Antron 99 or Imax 2000. The radial kit is not needed at all.

    More good luck
     
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  7. W9WD

    W9WD Guest

    Can't you just remove the radials from the omni and use the yagi elements for the ground plane?
    That's what I'm going to do
     
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    Last edited by a moderator: Jun 7, 2009
  8. Maniac373

    Maniac373 Base Station Extrordinare

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    The Aluminum pipe I am going with is 24 feet long. 2 inch outside diameter, 1/2 inch wall thickness, and 1 inch inside diameter-- the solid mounting bar on the omnidirectional antenna will slide right into the top of the mast. I will just have to run a bolt through the top of the mast to hold the antenna in place.

    you still think I need a set of guy wires? Do you think the mast pipe will bend with the omnidirectional antenna pictured up on top?

    The radials facing at a downward angle are active-- they help lower the angle of radiation so this 1/4 wave antenna will transmit similar to a 5/8 wave. They cannot be removed, the antenna will not work as it was originally designed.

    How far away would you recommend I mount the omnidirectional antenna above the beam?

    Charlie
     
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  9. Wire Weasel

    Wire Weasel Senior Moment

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    Hey Charlie, I'll agree with you that 2" alum. pipe with 1/2" wall thickness is going to be strong. But it's going to be heavy too at 24' long. That's a lot of wind load. But you can get away with it by using guys wires.

    I still say you don't need that much separation between them and you're going to alot of expense and trouble just to get your vertical up a little higher...

    Hey...more power to ya bro
     
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  10. Marconi

    Marconi Supporting Member

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    I agree with Wire Weasel, the mast is too long. I'm not even sure the Glenn Martain is rated or will support that big of mast at that length, plus the weight of that hugh beam. The wind load alone will be considerable without all that mast.

    You really need to check with Glenn Martain about the 40' beam even with a 5' foot mast. You need to check with your supplier of the Tailtwister and see if it is up to the tast with such a big beam, heavy duty or not.

    The Glenn Martain is probably not a good idea, you really need a good strong tower, maybe even free standing type that will take the torque and lateral energy that mother nature will send your way from time to time. The roof of your house was not built to withstand such business.

    After you get that stuff up on your roof you will immediately become the cause of every communication and electronic device problem in the neighborhood.

    Be safe and keep us posted.
     
    #10
  11. Captain Kilowatt

    Captain Kilowatt Professional Amateur Staff Member

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    I am surprised it has not been asked already but just what kind of antenna is the 40 foot long beam anyway? What band(s) does it cover? My concern is not so much with the mast and vertical (well a little bit) but rather with the ability of the Glen Martin roof tower to support such a large antenna regardless of how well the roof is reinforced.Roof mounted antennas are subjected to a lot of weird wind forces that result from uplifts caused bu the angle of the roof and this places odd bending moments on such a large antenna. Again, what is the model of the antenna?
     
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  12. W5LZ

    W5LZ Crotchety Old Bastard

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    I think you've already gotten some very good advice, talk to 'Glen Martin' about what you propose to do. It would only be a guess, but I think I can tell you what you will be advised to do/not do. I also think you can guess what that 'guess' would be, right?
    - 'Doc


    Completely beside the point...
    The only antenna with a 40 foot boom that I've -any- experience with definitely was not for 11 meters. It was also not something the average person would ever have to worry about putting up. Oh, I'd love to have one! But not after seeing the 'mechanics' of the thing. It was built to 'government specifications' sort of, and considering the weather where it was erected, that's a very good idea!
     
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  13. rfoverlord

    rfoverlord guardian of freedom

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    I'm kinda curious myself, since my tennadydyne has a 24ft. boom and 38ft. ele. and as far as that vertical he would be better off with something less gimicky like a 10K or even a V58 with one of those you wouldn't need that much mast. I would, if you already have the mast, go ahead and mount the vertical on it and find a way to get it upright on a calm day and see how much it sways while it's on the ground
     
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  14. Maniac373

    Maniac373 Base Station Extrordinare

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    I have rethought this idea, and decided that the 40' boom isn't practical for the area I am trying to install. Now I am thinking of going with a Signal Engineering Lightning 4+ Quad antenna (real close to an 18' boom), with a ham IV rotor inside the Glen Martin RT-936 rooftop tower. I have a med duty Rohn BX series tower that is 40' tall-- Im just going to mount the merlin omni antenna up on top, on the other side of the yard-- far enough away so that the Quad wont come in contact with it when it turns.

    Charlie
     
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  15. linearone

    linearone King of NY

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    you keep arguing with logic and reason and disagreeing with the guys who have done this before and can tell you ti wont work yet you STILL argue the point. If you know what you are doing and are sure that 24 ft of 1/2" thick pipe will work then by all means do it. Please be sure to scan the copy of the home owners insurance claim before you submit it when it falls off the roof and kills the neighbors kid.
     
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