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

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Old 06-06-2009, 07:11 PM
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Default need advice on how to properly install large boom antenna on roof tower


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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Old 06-06-2009, 08:55 PM
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safest way would probably be to use a bucket truck.
just my .02
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Old 06-07-2009, 07:16 AM
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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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Old 06-07-2009, 07:46 AM
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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 by Wire Weasel; 06-07-2009 at 08:36 AM.

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Old 06-07-2009, 10:09 AM
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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)


Charlie

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Old 06-07-2009, 11:39 AM
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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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Old 06-07-2009, 12:08 PM
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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

Last edited by W9WD; 06-07-2009 at 01:35 PM.

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Old 06-07-2009, 02:37 PM
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Quote:
Originally Posted by Wire Weasel View Post
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 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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