Question: Best way to install vertical antenna on a flat surface? Gap Titan DX

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by CT2FZI, Mar 2, 2020.

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  1. CT2FZI

    CT2FZI Ham Member QRZ Page

    Hello everyone,

    First of all thank you in advance for your time and advise.

    I would like to install a GAP Titan DX on a flat surface I have on my roof, but I am short of ideas...

    I will be able to have 2 sets/heights of guy wires easily, but I would like to install the antenna on the top of a 2 metre/6.5 feet and I would like to decently support this 2m tube.

    I have this photo with the surface itself:

    [​IMG]
    [​IMG]

    (on the left OH2EC multiband dipole home made and on the right X510)

    Cheers and all the best.

    Luís CT2FZI
     
  2. K7TRF

    K7TRF Premium Subscriber QRZ Page

    The typical approach is to use a Non Penetrating Roof Mount with sand bags or other weights to hold the antenna which of course would have to be guyed as well.

    There are various commercial versions of a Non Penetrating Roof Mount or you could build something that does the same job but they look like this:
    [​IMG]
     
    EA1DDO, AJ6O, AK5B and 1 other person like this.
  3. W9WQA

    W9WQA Ham Member QRZ Page

    i put up a tv ant on a tripod mounted on 3 2x6 treated 8 ft boards arranged in a triangle. used cement blocks to hold it down, NOTHING ELSE . no guys twenty yrs ago.
    saw it last week. looks fine.
    good size tv ants pretty heavy.
     
  4. CT2FZI

    CT2FZI Ham Member QRZ Page

    Thank you both for your inputs.

    @K7TRF I am able to perfurate and bolt any kind of metal structure under that surface, its made of concrete.
    Your solution looks fine, but I am not sure if it can hold this antenna over 2 metres metal tube, over a 12 story building... hihi Ground level maybe ok...

    Cheers!
     
  5. K7TRF

    K7TRF Premium Subscriber QRZ Page

    It's used to hold tall and heavy antennas all the time. The key is heavy weights on the base (sand bags or concrete blocks) and for a tall antenna or one with substantial wind load you should also guy the antenna itself. These mounts are designed for roof top, not ground use.

    That said, if you can penetrate the roof then I'd use a standard roof mount tower with 10mm or 12mm diameter concrete expansion bolts. You'll still probably want to guy your antenna but you can have a rock solid mount if you don't mind drilling the concrete roof. In that case I'd recommend a 4 legged roof mount tower like this:
    https://www.amazon.com/Glen-Martin-...ocphy=9029376&hvtargid=pla-573885292732&psc=1

    [​IMG]
     
    AK5B likes this.
  6. KH6AQ

    KH6AQ Ham Member QRZ Page

    Let's look at the forces on the mount/roof interface.

    Inputs
    Gap Titan DX height 29 ft. with 4 sq ft wind load (my estimate). This is 8.8 m and 0.37 sq m.
    Mast 6.28 ft (2 meters)
    3 Guys at the top of the 2 m mast

    Outputs
    Antenna wind force at 100 km/hr is 193 N
    Lever arm is 4.4 m on one side and 2 m on the other side
    Roof/mount interface sideways force is 193 N x 4.4/2 = 425 N (about 100 lbs)
    Max guy horizontal force is 670 N (about 150 lbs)
    For guys at a 45 deg slope tension is 950 N (about 220 lbs)
    Note: the wind loading of the 2 meter mast is not included in the calculation and I can recalculate to account for the mast.

    From this and the the mount/roof interface base dimensions the horizontal and vertical forces on the interface points can be calculated (forces on the bolts or clamps).

    Outputs
    Antenna + mast wind load 5 sq ft (0.46 sq m) 240 N acting at 5 m above the base
    Guy horizontal force is 600N
    Roof/mount interface sideways force is 193 N x 4.4/2 = 425 N (about 100 lbs)
    Max guy horizontal force is 670 N (about 150 lbs)
    For guys at a 45 deg slope tension is 950 N (about 220 lbs)
    Note: the wind loading of the 2 meter mast is not included in the calculation

    From this and the the mount/roof interface base dimensions the horizontal and vertical forces on the interface points can be calculated (forces on the bolts or clamps).
     
    Last edited: Mar 3, 2020
    CT2FZI and AK5B like this.
  7. CT2FZI

    CT2FZI Ham Member QRZ Page

    Well I will do my best to use it this summer... Hopefully the sunspots will help the DX :)
     
  8. AJ6O

    AJ6O Ham Member QRZ Page

    Nothing like having a multistory building as a tower. How cool is that? :)
     
    AK5B and CT2FZI like this.
  9. CT2FZI

    CT2FZI Ham Member QRZ Page

    HIHI you made me smile, but I am wondering how big will the roof work as ground. One should consider "distance to ground" from the roof I guess... The Titan DX does not need tuner, and no radials [the ones at the antenna work on 80m only from what I can tell] so I guess it will be noisy but better than my trapped dipole.

    Cheers!

    Luis, CT2FZI
     
  10. AJ6O

    AJ6O Ham Member QRZ Page

    Being a retired "Electrician" I like using 1-1/2 EMT, and 1-/4 EMT to make short masts. Heavy-duty angle brackets work great!

    AntennaMount1.jpg
     
    AK5B likes this.

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