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HexBeam + Rohn H50 + RT-424 ?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF6ABU, Jan 27, 2011.

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  1. KF6ABU

    KF6ABU Ham Member QRZ Page

    I’m trying to come up with a directional solution. I am a property renter.

    My idea is a Glen Martin RT-424 on the ground (securely) with my Yaesu 450 rotor and thrust bearing in the RT-424, a Rohn H50 telescoping mast with the top section removed, to a hex beam probably from DX Engineering. The H50 will be secured to the eaves of the house at the 2nd story level in a way that allows it to still rotate (is the plan).

    I think this will leave about 15ft of mast part extended past the eave brace. Does this sound OK? I live in Southern California.. No snow or ice, occasional wind of SoCal strength (not really sure of the MPH). I was thinking in this way no guys would be needed.

    Access to, and installation of the beam would take place on the second story roof.
     
  2. N4ERZ

    N4ERZ XML Subscriber QRZ Page

    Does that put the hex beam above your roof in the clear or tucked away "behind" the roof?
     
  3. K5PO

    K5PO XML Subscriber QRZ Page

    I was debating a similar setup with a hex beam on a Rohn telescoping mast. I was concerned that even with the light weight and wind surface or the hex beam, it and the rotator may exceed the Rohn mast's capabilities. Hope to hear the thoughts of others.
     
  4. KF6ABU

    KF6ABU Ham Member QRZ Page

    Above the roof, in the clear.

    The rotor will be down below, so the only windload and weight will be the hexbeam. Its about 20lbs and maybe 5lbs of wind resistance.
     
  5. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    36' of mast rotating above the RT is a lot. Alignment to a very good rotary bearing attached to the house will be extremely critical: If you miss by a tenth of an inch, it's not going to rotate.

    Even with a house mounted bearing, unless that's up very high (like >20' above ground) the mast will not self support with any load on it at all. The H50 was designed to be guyed every ten feet (five sets of guys).

    This might work if you guy it just below the beam (as small a load as that is) using a rotating guy ring, which the H50 does come with standard. Three guys at that location, with 120 degrees between the guys, will probably make this work. But alignment of the tower, rotator, RT thrust bearing, and house bearing is very critical. If there's a one degree tilt, this probably won't work. But with perfect alignment, it probably will.

    It would be better to put the RT on the roof with a much shorter mast, and make it a "non permanent" installation. Many good ways to do that, so once it's removed there will be no trace it was ever there.
     
  6. KF6ABU

    KF6ABU Ham Member QRZ Page

    The eave where it will attach is certainly over 20ft high.

    I can add a guy in 3 or maybe even 4 directions above the roof, not the end of the world.

    I can guy the mast below the roof level at 12ft or so without an issue using a guy ring but only in 2 locations due to it being against a wall.

    What about a guy 12ft or so, a U-Bolt with close spacing keeping it secure but still rotatable to the eave, then another guy above that? At the level below the roof the mast is nestled in a way and not exposed to wind at all

     
  7. KF6ABU

    KF6ABU Ham Member QRZ Page

    I am not to confident I will be able to do that...
     
  8. WA8FOZ

    WA8FOZ Premium Subscriber QRZ Page

    Yes. And I have done just that, many years ago in college atop an apartment where I lived. I had a Mosley MP-33 (TA-33jr with beefed-up traps), which I suspect was hevier than the hex beam. It worked fine. Good luck!
     
  9. KF6ABU

    KF6ABU Ham Member QRZ Page


    Hey Bill!!

    Can you describe your old set up with some detail?

    Thanks!
     
  10. KF6ABU

    KF6ABU Ham Member QRZ Page

    If its attatched to the eaves 20ft up or so, there wouldnt need to be any guying below that level right? If i attatrched it to the eaves in a snug fitting U-bolt that still allowed it to rotate but didnt let it move around to much would that be sufficient at that level? And then a guy every 10ft above that?
     
  11. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Try it and let us know how it works! I'd think a very strong rotator might be required. A snug fitting but slightly loose U-bolt isn't a real thrust bearing. On a windy day the wind could blow the mast against this and cause serious interference. If you guy above that, you'd need to be sure the guys were very, very well equalized to keep the mast completely vertical under all conditions. But if everything is done just right, it would probably work.;)
     
  12. KF6ABU

    KF6ABU Ham Member QRZ Page

    Thanks for all the help you have been giving. The rotor is a yaesu 450, so it should be fairly substantial for this task (Rohn H50 + 20lb hexbeam). I could use a thrust bearing at the eaves.. maybe with a L steel bracket of some sort.. It's just the alignment has me somewhat worried about getting it "perfect". Would the process to do this be: Put mast in 4.5ft roof tower with thrust bearing (not in rotor yet) then put upper thrust bearing on and then to eaves and make sure it still rotates? The mast will not be right against the eaves of the house. The eaves come out about 4 inches from the wall, and with the glen martin tower at ground level im guessing that puts the mast a foot or so from the eave.

    The other option would be to sink a 4x4 vertically into the ground and make a tray for the rotor and thrust bearing and use that instead. I would be able to get the mast much closer to the eaves in that case.
     
  13. WA8FOZ

    WA8FOZ Premium Subscriber QRZ Page

    Sorry I've been away from this thread. Here's what I did.

    1) 10-foot tripod on a flat roof. Feet of tripod screwed onto 2 X 4s - Weights on the 2 x 4s - it would have been better to drill it onto the roof, but not allowed. Top of tripod guyed
    2) Rotor inside tripod.
    3) 10-foot mast attched to rotor. Beam attached to mast

    Then, I went up:
    4) additional 10 feet of mast, guyed at midpoint with a floating guy ring.. Guys to same attachment points as lower guys.

    When I moved into my first house, I did the same sort of thing until I could put up a tower.
    5) Tripod on ground, beside the house, with its apex under the edge of the eave.
    6) Collar attaced to eave, through which the mast turned (just a pipe slightly wider than the mast)

    Hope this helps.
     
  14. KF6ABU

    KF6ABU Ham Member QRZ Page

    What was the collar you used? PVC?
     
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