Been asked before but here it is again

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by W5NNX, Nov 21, 2020.

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  1. W5NNX

    W5NNX Ham Member QRZ Page

    If you have a 10 or 12 foot mast with like 8 feet above the tower, can you stack an HF yagi at the bottom (at the top of the tower), a rotatable warc antenna up next and a vhf (6 meter) above that on the same mast? I realize the spacing isn't optimum but I have seen some folks stack a lot, 1-2 to 3 feet apart. Other then using the 1/2 the boom length as a guide, since there isn't enough room there, what would be considered the absolute minimum. The Warc would be parrell to the booms of the other two since only one element.
     
  2. WB8NQW

    WB8NQW Ham Member QRZ Page

    I have a 3 element 6 meter beam 3 or 4 feet above a Mosley TA-33 on a 40 foot tower. Do they interfere? Who knows or cares. It is what I had available.
    A longer mast would need to be strong enough to securely hold whatever you put at the top of it.
     
    AK5B and WD4ELG like this.
  3. W5NNX

    W5NNX Ham Member QRZ Page

    That is a correct statement...
     
  4. W4HWD

    W4HWD Platinum Subscriber Platinum Subscriber QRZ Page

    Use what you got because optimum doesn't matter if you ain't got it.
     
    AK5B and WD4ELG like this.
  5. W5NNX

    W5NNX Ham Member QRZ Page

    The Warc dipole would be same field as the HF Yagi, boom and boom pointing same direction. I think I have seen an HF yagi design somewhere with the WARC part in the boom. Going to look that up.
     
  6. W5NNX

    W5NNX Ham Member QRZ Page

    that would be the obvious...curious about interaction, pattern skewing, etc. Don't think if the warc is in the same direction as the HF yagi boom.
     
  7. WA7F

    WA7F Premium Subscriber QRZ Page

    That’s a refreshing question. I thought it was going to be the, “Can you use a metal roof for a ground plane” question that comes up about every two weeks.

    It sounds like you have an decent answer so I won’t reiterate. Have fun.
     
    AK5B likes this.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    If the WARC rotary dipole is "parallel to the booms" of the other two, then your rotator readings will be 90 degrees off for that; I'm not sure that's even a great idea, but it probably depends on the boom lengths of the other antennas.

    Maybe you meant "parallel to the elements?"

    In any case, if the tower is rated for the intended load at the extended height of a longer mast, I'd replace the mast with a longer one, even if that means using a heavier-duty mast.

    Everything's a compromise, but at home my 55' tower has a 15' mast with about 3' inside the tower (to the rotator) and 12' above the thrust bearing, and I have the HF LPDA beam right above the bearing, then a 6m beam 6' above that and a 2m beam about 6' above that.

    Yes, there is absolutely interaction. One way I can tell is if I transmit on HF and look at "reflected power" on the 6m wattmeter...there it is! Happens vice-versa, also: If I transmit with power on 6m and look at "reflected power" on the HF wattmeter, there it is! So, of course there's interaction. However it doesn't seem so substantial that it prevents any of the antennas from working about as I expected them to.

    That's highly scientific.:p:rolleyes:
     
    WA4SIX likes this.
  9. N2IPH

    N2IPH Premium Subscriber QRZ Page

    Or one antenna that covers all the bands you want to work.
    • No interaction
    • Lower wind loading from less square footage and single antenna can be mounted closer to tower, extended mast not required.
    • Reduced strain on rotator from lower mass
    • Lower rotational force required during starts/stops
     
    AK5B likes this.
  10. W5NNX

    W5NNX Ham Member QRZ Page

    would be nice to have the funds to revisit an entire antenna system replacement, doubt the wind loading would be less and in this area, wind is a big issue. Pie in the sky.
     
    AK5B likes this.

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