Beam Antenna for my US Tower MA-550

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KF7LPU, Nov 21, 2021.

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  1. KF7LPU

    KF7LPU Premium Subscriber QRZ Page

    Looking for opinions and advice on antenna choice. I just setup a US Tower MA-550 tubular tower on my property (7500 sq ft area, includes house 1800 sq ft). The antenna is in the side yard with 15 feet of area for turning when the tower is collapsed (22 ft high) and 50 feet when at 55 ft. So I am trying to decide what antenna to put on top that gives me the best bang for buck vs performance.

    The larger the antenna the smaller the wind load so I want something that is reasonable for wind in the Sacramento area. I plan to top load my rotator (Yaesu G-800) on the tower with a k-factor max allowance of 180. My interest is at a minimum have access to 20-6m bands, but would really like to have 40/30m if possible. I have been considering the following options not for price but for quality. I am open to other options if they meet the quality and performance mark.

    Option 1: A Steppir DB11 for beam and maybe a sloper to cover 40 and 80.
    - https://consumer-steppir.tempurl.ho...na-products/db11-yagi-antenna-20m-6m-package/

    Option 2: Steppir 2 element with 40/30 addition as a folded dipole
    - https://consumer-steppir.tempurl.ho...enna-products/2-element-yagi-antenna-package/

    Option 3: Steppir Urbanbeam with 40/30 addition a folded dipole
    - https://consumer-steppir.tempurl.ho...2-element-antenna-products/urbanbeam-package/

    Option 4: Steppir 3 element
    - https://consumer-steppir.tempurl.ho...enna-products/3-element-yagi-antenna-package/
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd have chosen a Tennadyne T11 but not sure it's even available.

    Evidently Tennadyne/Cubex just changed ownership and the new owner is relocating the company so I don't know what "deliveries" might be...or even if there are any.

    For the DB11 I'd choose a bigger rotator than the G800.
     
  3. KF7LPU

    KF7LPU Premium Subscriber QRZ Page

    Tennadyne has some great antennas, but one thing I need to be careful of is top weight. I am held to a max antenna weight of 60 lbs. There are weight allowances for rotator and cable, etc, but the antenna is pretty much set.
     
  4. NG1H

    NG1H XML Subscriber QRZ Page

    1) At what height does the 15' radius restriction kick in?
    2) Is the restriction completely around or is it possible that a longer antenna will fit if turned to a specific direction?
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The DB11 is 63 lbs.

    But I'd be much more concerned with wind load (square feet), frankly.

    The T-11 may be "too big" for that tower/rotator combination.

    Also you wrote about a pretty big difference in allowable "area" when the tower is nested vs. when it's extended: Is that because trees are in the way, or what causes the difference?
     
  6. KF7LPU

    KF7LPU Premium Subscriber QRZ Page

    The tower base was centered between my neighbors and my house. The is roughly 25-30ft of spacing and I would rather not upset my neighbor with elements hanging in their yard when I collapse the tower. Now if I rotate the boom I could probably keep everything on my side.
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Note: If you take the published specification seriously, you couldn't install any kind of multiband HF beam on the MA-550 as the same spec that limits the antenna weight to 60 lbs also limits the wind load surface area to 1.5 square feet. There isn't any kind of multiband HF beam that doesn't greatly exceed that.

    But the limitations are all based on a 70 mph wind speed. If you do get that and the tower is extended, the limitations published are reasonable. But if you don't, then way bigger and heavier antennas can be safely used and the UST web page for the MA-550 even shows one installed on it!:)

    The serious limitation with the MA towers is the top section which is just heavy duty .120" wall "mast" and the weak link in the entire tower. But that's what they chose to use for the upper 20' section and if you don't rotate the tower from the base but use a top-mounted rotator, you're kinda stuck with that limitation.
     
  8. KF7LPU

    KF7LPU Premium Subscriber QRZ Page

    Well good news is US Tower sent me a recently update spec for the tower. So I have more room for cushion.

    Ultimate Wind Velocity Vu Basic Wind Velocity Vasd: 110 mph
    - 3 second gust 85 mph 3 second gust

    Allowable Antenna Wind Load - Unfactored (lbs): 187 Max.
    Allowable Antenna Weight (lbs): 100 Max. Allowable Antenna Effective Wind Area (sq. ft.): 12.0
     

    Attached Files:

    NY6G likes this.
  9. KF7LPU

    KF7LPU Premium Subscriber QRZ Page

    The tower base was centered between my neighbors and my house. The is roughly 25-30ft of spacing and I would rather not upset my neighbor with elements hanging in their yard when I collapse the tower ~26ft. Now if I rotate the boom I could probably keep everything on my side.
     
  10. KH6AQ

    KH6AQ XML Subscriber QRZ Page

    Is the updated spec sheet for the fully retracted position? It says Mast Shall be Fully retracted for wind speeds above 50 mph. When calculating the wind speed for which 12 sq ft of antenna exerts 187 lbs of force I get 70 mph.
     
    Last edited: Nov 23, 2021

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