Quagi antenna

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by KA0EIV, Nov 2, 2016.

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  1. KA0EIV

    KA0EIV Ham Member QRZ Page

    Ok I have been playing with my 2meter quagi I built 2 months ago. It seems to work good, as I get good signal reports with it on the 20'tower, but its seems to me that f/b ratio needs improved. Can I throw another wire loop in the reflector say half way between boom and existing loop to improve f/b. or do I try adjusting r-de spacing? I can't seem to find any info on how to optimize this antenna just info on how to build it. Do I just set it aside and build a direct feed type yagi to play with. I have a little more time to play as I have to wait till sub zero weather to transfer antennas to my 50' tower cause I have always found the colder adverse conditions you do antenna work in the better the antennas perform!!
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Did you build it exactly per the N6NB Quagi design article, which used a non-conductive (bamboo) boom and insulated household hard drawn copper wire loops, etc?

    If so, it's F/R is about 20 dB, I've built a lot of these.

    Adding another reflector won't make it better, but will degrade both gain and the impedance match. The reason the Quagi can be directly fed with coax and no matching devices is with the element sizes and spacing published, the driven element loop is very close to 50 Ohms, non-reactive. Change anything, and it won't be.
     
    W0BTU likes this.
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Listen to Steve! ^

    My 8 element 2m Quagis worked very well indeed (link). I scaled all of the dimensions in Wayne's article down to 144.200. My booms were made from clear pine coated with clear marine spar varnish.

    See http://n6nb.com/quagi.htm

    You have to follow the directions in the article exactly, even to the type of wire and insulation used for the loops. I used aluminum rod for the directors, and that worked fine.
     
    KA0HCP likes this.
  4. KA0EIV

    KA0EIV Ham Member QRZ Page

    I used 1.25 fiberglass tubing for the boom and 1/4" fiberglass rods for the spreaders with #12 insulated wire for loops. match on the driven element was good right from the get-go, swr 1.2 across the band. I've just noticed if the antenna is pointed away from a very strong signal it doesn't block it as much as the 5el quad did I used before. It does good, heading at the signal is 5/7-9, heading away is no needle movement on S meter but hear the audio above the noise floor. the old 5 el. would block it out on the back side.
     
  5. W0BTU

    W0BTU Ham Member QRZ Page

    Anyone happen to have an antenna model file for that 8-element Quagi? I'd like to see the pattern.
     
  6. W1VT

    W1VT Ham Member QRZ Page

    I've been to antenna forums where the designers told the audience how it was designed--two guys on a test range--one to make changes and another to take measurements. They found if one guy did both it would bias the measurements.
     
  7. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    I think it may have been "partly" that, but mostly to expedite the tests so one person didn't have to run around so much.

    The "two guys" are still around: Wayne Overbeck, N6NB and Wil Anderson, AA6DD. Both still very active VHF'ers. The "test range" was a beach, which isn't a bad choice since it's flat and there's nothing around to create reflections other than the ground which is everywhere anyway.
     
  8. KF6A

    KF6A Ham Member QRZ Page

    Personally I would build a yagi.
     
  9. KF6A

    KF6A Ham Member QRZ Page

    2m 8L quagi FS azimuth pattern. 163.456" from reflector loop to last director. Dimensions were taken from a VE3SQB quagi generator.

    [​IMG]
     
    W0BTU likes this.
  10. KF6A

    KF6A Ham Member QRZ Page

    Here's a modern computer optimized 2m 8L yagi. 154" from reflector to last director.

    [​IMG]
     
    W0BTU likes this.

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