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ROHN Allowable vs. Effective table help?

Discussion in 'Amateur Radio Antennas' started by PA770, Jan 9, 2019.

  1. Blackcat630

    Blackcat630 Sr. Member

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    A couple things,



    I will definitely echo the quality of Norms fabrications. I dealt with them for my 45g rotor plate. Nice people to deal with, reasonably priced and good quality.

    If you are only going 30 ft with a 3 element and a vertical above that, I think 45g might be over kill. I don't know what kind of winds you deal with or ice but at only 30 ft with your wind load... 25g would probably suffice. With that said... If you would ever like to put a larger antenna in the future or add another 10 ft section (un guyed) you might want to go with 45.
     
    Captain Kilowatt likes this.

  2. PA770

    PA770 W9WDX Member

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    The Maco 103 is 3.99 sq ft and I don't know the load on the A99.. thinking 1.5 or less. So like 5.5 total for both.

    The 25G says like 5.3 in 100 mph at 30' on the G sheet as shown on page 1 of this post.
     
  3. Blackcat630

    Blackcat630 Sr. Member

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    Sounds like it should play just fine...
     
  4. oldtymer

    oldtymer Member

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    Stick with 2" mast & definitely use a thrust bearing.
     
  5. PA770

    PA770 W9WDX Member

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    So the AG3 top section would be out unless I get a shelf and add a bearing..

    How do people get away with out a bearing on some of those setups??

    Very conflicting.
     
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    You NEED something at the top to take the sideways bending away from the rotator. Usually that is done with a bearing however some operators successfully use a top section with a sleeve that the mast fits inside and freely rotates inside. It does the same thing. That AG3 top section will do the same thing. Using a bearing also will allow you take the weight off the rotator whereas the AG3 top section will not. This is not a concern with what you propose however as it is not very heavy at all. Once you start talking a couple hundred pounds of mast/antenna weight it is HIGHLY recommended to use a bearing but by then you would be far outside thew ratings of Rohn 25 anyway.
     
    Shadetree Mechanic and PA770 like this.
  7. PA770

    PA770 W9WDX Member

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    Thank you.. just started a new thread to focus on the set-up aspect.. hopefully that doesn't aggravate you too much Cap't..
     
  8. Blackcat630

    Blackcat630 Sr. Member

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    IMO......If you use a decent rotor and the AG3 I really don't think the thrust bearing is necessary. The downward force of the mast and 3 element / a99 shouldn't be all that much on a decent rotor. The nose cone will take away the side ways bending as Capt K mentioned.
     
    Captain Kilowatt likes this.
  9. oldtymer

    oldtymer Member

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    No the tapered top would not be useless but the thrust bearing allows for expansion
    if you wish to put a bigger beam or stack a 6 meter or vhf antenna up there.
    Plan for the future not the present.
     
    Blackcat630 and BJ radionut like this.

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