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hey HomerBB ...............

Discussion in 'Home Brew' started by BOOTY MONSTER, Nov 12, 2010.

  1. could you post some pics of your gamma on your home brewed sigma ? or if they're already posted in a thread here can you link to the page in the thread that has them ? could you also describe the materials and construction of your gamma ?

    thanks ;)

    if anyone else would like to share info on home brewing gammas and/or provide pics of theirs id appreciate it also :)


     

  2. bob85

    bob85 Supporting Member

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  3. thanks bob . so there is no continuity between the rod and the tube in the gamma ... the plastic tubing insulates them from each other %100 ?
    correct ???
     
  4. bob85

    bob85 Supporting Member

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    yes;)
     
  5. jazzsinger

    jazzsinger Bullshit Buster

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    i just love it when bob gives these highly technically detailed answers.:LOL::LOL::LOL::LOL::LOL::LOL:;)
     
  6. mackmobile43

    mackmobile43 Jock Supporter

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    He has a way with words and does not discriminate between those technically minded or me. :D

    Booty the gamma is a large air space capacitor.
     
  7. HomerBB

    HomerBB Sr. Member

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    BM,
    As I recall I used Bob's dimensions to make my gamma. the exception would be that I used electrical tape along the rod inside the sleeve at various places instead of the plastic tube. I did not have a hose/tube that would go around my rod and also fit in the tube.

    Here is the link to that info:Bob's Post http://www.worldwidedx.com/cb-antennas/31799-avanti-sigma4-alternative-view-point-27.html#post226120

    Here's the only photos of the gamma I posted (not so good): Homer's Post http://www.worldwidedx.com/cb-antennas/31799-avanti-sigma4-alternative-view-point-28.html#post226365

    And many thanks to Bob for that info. So many helpful suggestions came from that thread I can't imagine ever having gotten a working model together without them. The gamma was the feather in the hat to making the match I sought.
     
  8. bob85

    bob85 Supporting Member

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    lol;)
     

  9. is there a little room for error in these measurements ?
    is the .512 tube the inside or outside diameter ?
    could i use 1/4 inch rod and 1/2 inch inside diameter tube ............. ?
    ............ with about 1/8 inch of insulating material between them ?
    at what height from the base of the vertical does the bracket for the top of the gamma connect to the vertical ?
    how far out from the vertical is the bottom of the gamma ?
    how far out from the vertical is the top bracket of the gama ?
    im assuming the antenna tuned by adjusting the rod length in the gamma tube tube .
    is the top gamma bracket used in the tuning also ? or is it a set position ?


    a 31 ft vertical seems to get the most performance from the sigma styles . if using much larger diameter tubing (six 6 ft sections from 1 inch on top to 1 3/4 at the bottom) will there need to be any length compensating for the increased surface area/diameter ?

    thanks
     
  10. HomerBB

    HomerBB Sr. Member

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    My experience is this antenna is more sensitive to its dimensions and settings than any other I've done. There may be forgiveness in it, but, if so, it is close.
    I used 1/2 ID tube
    yes
    yes
    varies with tune
    about the same as the radials
    I don't recall anyone discussing this. i just went with what i always have on a yagi. 4"
    yes, partly
    yes, this, too
    Only after the match is found
    Someone else will have to give you an answer for this but I would think it would affect the antenna length some.
    Sure.
    Now that I've put my answers in here maybe someone smarter can improve upon them.
     
  11. thanks homer . very encouraging ;)
    what did you use for insulating the gamma sections ? i was thinking about heat shrink wrap or electrical tape with enough layers to keep the rod snug in the tube . maybe if im very lucky lowes or home depot may carry some tubing thats ..... close enough to a perfect fit . i know lowes (and home depot too i think) carries 3 ft sections of aluminium rods and tubing in different diameters . if they have them in the needed diameters it would make things pretty easy....... if i get brave enough to try to make one .
     
  12. HomerBB

    HomerBB Sr. Member

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    I used wraps of electrical tape to make the fit. Yes, you can get your aluminum rod from either of those stores. I did.
     
  13. sweet . thank you sir :)

    if i made this gamma is there any reason it would work for tuning a half wave dipole ... like the driver on a beam or the sirio 27 dipole ?
    and..... if....if it works on that will it work on a sigma style/copy ?
     
  14. if.... if i wanted to try to make a sigma style antenna this spring would my base plate that im currently using be too big ? or rather big enough to cause problems ?

    [​IMG]

    its about 12 inches square (30ish cm) . if i can make a working gamma attaching it , the vertical and 4 ground elements going up to the hoop would be very very easy . its a very strong platform to build on .
     
  15. bob85

    bob85 Supporting Member

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    you could make a direct fed open sleeve with that baseplate and isolator,

    if you want a sigma/vector i would make it look like a sigma/vector complete with gamma ;)
     

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