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2 Element Quad

Discussion in 'CB Antennas' started by HomerBB, May 13, 2009.

  1. HomerBB

    HomerBB Sr. Member

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    Nope. I'd have to add on to it.
    Boom is 1 1/4" fence top rail with 1 1/4" PVC at each end to facilitate in and out movement for spacing. Spreaders are similar to your plywood, except they are there to keep the arms rigid only. The hubs are 4-way PVC connectors drilled through the flat side center and drawn against the boom ends with eye bolts around bolts in the boom ends at the right depth from the end. The angles are shelf brackets for wire storage systems to keep things rigid on the boom axis direction. (Whew...)
    Yep. Other than a very fragile prototype to test the possibility.

     

  2. RickC.

    RickC. Hopeless antenna junkie

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    This is the only pic of the one I had that's still in my Photobucket thing:

    [​IMG]

    This was when I was first testing it before it was raised all the way up. The boom is 2x2 pine and the mast to boom plate is 3/8" exterior ply that I fiberglassed.

    It held up well in the wind, the only problem being a couple of times the U bolt didn't hold the refelctor so well and it tilted in about two feet toward the center. Your design with the bracket arms will keep that from happening.

    So mine was pretty low-tech, yeah... But that thing bounced around in some high winds to the point that I was sure I'd come out the next morning to find nothing but sticks and wires hanging there, but other than what I just mentioned I never had a minute's trouble from this quad and didn't have to do a thing to tune it, ever.

    Experimentation is what it's all about though, and thanks again for the 1/12 wave info. I recall seeing that some time back but didn't pay much attention to it.
     
  3. HomerBB

    HomerBB Sr. Member

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    Looks good to me. It performed well, I suppose...?

    I took only one not-so-good photo of the prototype:

    [​IMG]
     
  4. RickC.

    RickC. Hopeless antenna junkie

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    Thanks Homer,

    And it did perform very well. The only reason I took it down was I wanted to put up a 2 element triband yagi, and the place this quad stood was the only spot available. I later used the wire for a 20m Moxon that I never was all that thrilled with.

    Altogether I think I had about 55 bucks in that quad and about 10 of that was the flat black paint, and that was with buying the lumber, angle aluminum (which was the most expensive part) and antenna wire new. If I were an avid CBer it would still be up.

    Your prototype, I'm guessing that's PVC, how do you have that attached to the boom?

    I wish quads saw more use on the higher bands (and 11m) where they're easier to build and handle. They can be a bit of a pain as far as the logistics at first but dB/dollar you can't beat them. Lowe's sells these 8' plastic garden rod things, and if I ever build another quad for the upper HF bands I think I'm gonna use those.
     
  5. HomerBB

    HomerBB Sr. Member

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    Useless. We sell them at The Home Depot, too (as does Walmart).

    They are metal tubes wrapped with plastic. They are lighter that way, but would resonate if used as spreaders.

    I have some and think that later I will retry to build a delta matched two element Yagi with them as the end sections of the elements.
     
  6. HomerBB

    HomerBB Sr. Member

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    They were attached to PVC end pieces over the top rail just like the other one. They "L" shelf brackets were used to hold them in place. Like this:

    l
    l
    L______
    xxxxxxxxxx=================+++++++++++++===


    l
    l
    L______ is "L" bracket 9" x11"

    xxxxxxxxx is copper tube 3/4" x 1'

    ===== is cpvc 1/2"

    ++++++ is wood dowel 3/8"


    Hope that's clear???
    This is not a photo of my prototype. Just shows the brackets of the type I used on it.

    [​IMG]
     
  7. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    For anyone interested in making a quad antenna I highly reccomend looking at Max Gain Systems for parts. They are not the cheapest place in the world IMHO but they do offer some great antenna components and the fiberglass spreaders are great.

    MAX-GAIN SYSTEMS, INC. : Fiberglass Price List

    I plan to purchase and hopefully install a new 56 foot tower this fall and then purchase the fiberglass spreaders from Max Gain Systems to build my own antenna. My plan is to build it over the winter/spring and install it next spring/summer. I have already drawn up the design details for it to be a five band quad for 10,12,15,17, and 20m. It will be two elements on 15,17, and 20m and hopefully three elements on 10 and 12m. Boy, the wife hates the footprint of my A3 tribander now,wait until she sees just how big the quad will be. :eek:
     
  8. HomerBB

    HomerBB Sr. Member

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    Thanks for the recommendation. The pricing doesn't look too bad to me.
    Is there a place you prefer we send the flowers?

    I think I hear organ music....
     
  9. JDemoret

    JDemoret Member

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    I used those rods for the ground radials for my omni (y).
     

    Attached Files:

  10. RickC.

    RickC. Hopeless antenna junkie

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    Ha!

    I never had cut one of them open. The wood was cheaper anyway and was not any trouble other than having to paint them. You could only get away with that with small quads though.

    Homer, any luck with that reflector?
     
  11. HomerBB

    HomerBB Sr. Member

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    Not yet.
    I've gotten the SWR at 1:7:1 on ch40 and 1:2:1 on ch1, but the thing needs to be brought back down to change the reflector length. I am thinking on a way of doing it without taking it back down and not killing myself by falling off the house. . .
     
  12. HomerBB

    HomerBB Sr. Member

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    Yep. I've got some I'm considering using in some way.
     
  13. PA629

    PA629 Active Member

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    Another source for fiberglass is by using the flagsticks from a golf course. They work great in conjunction with aluminum tubing for the spreaders. I have a friend who's the Head Greenskeeper at a local country club for my source. So make friends with your local groundskeeper.

    (Another way that I'm not advocating is that not all courses take the flags in at night.;) But that's up to you.)
     
  14. HomerBB

    HomerBB Sr. Member

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    Great recommendation. Better not recommendation.
     
  15. RickC.

    RickC. Hopeless antenna junkie

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    Wow, I don't know how you'd do that without taking it down. Quads are very forgiving though, and it will probably still work-- mine worked well up into the 10m band but the f/b ratio wasn't nearly as good that far from the fc, which is probably what you'd see.

    You know (and you probably do know), one way of tuning a quad reflector is using a stub and adjusting it for minimum field strength off the back. If you have a couple of helpers and a FS meter, that would be a good way to fix that reflector- -and since you're already sort of in the ballpark with the reflector length the stub wouldn't have to be that long.

    The last open wire section I made (for my J-pole) used 1/2" PVC for spacers-- but I saw in Walmart yesterday they had plastic coat hangers for $1.83 per package. That would fill the bill perfectly for making a short open wire stub, and you could probably get away with 1" spacing-- you'd be adjusting it anyway so it's not critical.

    Rick
     

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