2 meter Yagi??(or other directionals)

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by KC2WDA, Nov 27, 2009.

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  1. KC2WDA

    KC2WDA QRZ Member QRZ Page

    Anyone got any input on a 2 meter yagi(or some sort of directional antenna), i've got a 10 ft beam and a bunch of round aluminum, 2 old tv antennas i've torn apart. I am looking to find relationships to length, distance of directors, ETC.. on gain, ohms, and other characteristics, I see all these claims of OH our's is the best, no ours is..... i cant seem to find much about the math or relationships.. any help is much appreciated.. even if its - go to the local library dummy...
     
  2. VE3PP

    VE3PP XML Subscriber QRZ Page

    Last edited: Nov 27, 2009
  3. KC2WDA

    KC2WDA QRZ Member QRZ Page

    I guess I misworded my question, I've looked at alot of these sites about designing your own, they all give me different dimensions, the one you sent me to, says that i can make one less than 2.2 wavelengths, others say its ok, and has i change the length of my beam, everything else changes with it? how if the # of elements doesnt change? is the spacing the same on a 12 element as it is on a 6 element? what do i adjust to get my 50 ohm impedance? are these questions i should - just try and see what happens? from what ive seem, the designs are more of guidlines, and people saying well this worked for me. and to tune? just adjust the driven element or do you adjust the reflector or any of the parasitic elements? or again, you guys can just say experiment and see what happens.
    thanks for all your help
     
  4. K9STH

    K9STH Ham Member QRZ Page

    You really have to adjust the matching device on the driven element to achieve the best "match". There is no exact formula for adjusting the spacing between elements, the element lengths, and so forth that will work every time to produce a proper match between the driven element and the coaxial cable.

    If you are looking for a design that works every time (if you follow the directions) and that does not require any special matching device then you really need to look at the quagi design. This is the best "cookbook" antenna design around. If you build it per the specifications it works the first time, every time.

    For details go to:

    http://commfaculty.fullerton.edu/woverbeck/quagi.htm

    Glen, K9STH
     
  5. W0BTU

    W0BTU Ham Member QRZ Page

    Quagis

    I agree 150%! I once had two of N6NB's quagis stacked vertically, and did they ever play on 144 MHz SSB & CW. Glen knows what he's talking about.
     
  6. AE5TE

    AE5TE Ham Member QRZ Page

    ECHO the quagi. The driven loop element matches to coax easy and eliminates the hassles one has trying to build a mechanically strong and properly matched dipole type element.
     
  7. W0BTU

    W0BTU Ham Member QRZ Page

    The only thing I did different from Wayne's quagi article was to stack them vertically, 8 feet apart and not the 11' horizontal stacking distance. Not only did I not want such a narrow beamwidth that horizontal stacking would have provided, I also wanted more RF directed at the horizon (and not wasted directed up at a higher angle).

    I also think I scaled the 144.5 MHz dimensions to 144.15; the spacings and element sizes would have been increased by 2.4%.
     
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