Balun on Loops

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by 4D1N, Nov 17, 2009.

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  1. 4D1N

    4D1N Ham Member QRZ Page

    Do we really need a balun for Quad loops? I'm planning to build separate loops on 15m / 20m / 40m. Wire with PVC Jacket or Braided wire? In horizontal loops, should I use coax or ladder line?
     
    Last edited: Nov 17, 2009
  2. W7IVK

    W7IVK Ham Member QRZ Page

    loops

    for horozontal loops NO BALUN
    for quads ether a 1/4wave 75ohm coax feed or gamma match
    but it depends on the design some can be fed directly
    i wouldnt put a balun on anything but a dipole
     
  3. K8JD

    K8JD Ham Member QRZ Page

    Why do I keep hearing "no balun" when a loop is considered Balanced and Coax feeders (quarterwave matching coax included) are Unbalanced.and that spells BalUn.
    Adding 1:1 baluns didn't hurt my 30 or 40M loops.
     
  4. KC9KHG

    KC9KHG Ham Member QRZ Page

    I don't have baluns on any of my dipoles either:eek:
     
  5. G3TXQ

    G3TXQ Ham Member QRZ Page

    Don't you mean your "tripoles" :)

    Steve G3TXQ
     
  6. R3BU

    R3BU Ham Member QRZ Page

    Exactly !
    Any dipole fed with coax is a "tripole".And how much of the RF current flows to the cable's breid depends on R of braid in this point.
    At list a RF choke over coax is needed."It does not ask a food" :)
    P.S. If to take the "R" of random wire, in our case the cable's braid ~600ohms, 73ohm(dipole) : 600ohm=~12%.The 12% of the total dipole's power
    will be radiated by coax breid.
     
    Last edited: Nov 17, 2009
  7. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    A balun is a good addition however, you can get away without it when the feed point is low such as the case of a coax fed dipole used at its usual 468/F
    length. When the feed point impedance increases as you move off the freq the antenna is cut for, the currents start to divide more readily as impedance looking down the braid looks more and more attractive. This was the case, without a doubt, for my loop when I used it off resonance (it was cut for 75M and I used it on 40M or 20M). 73, Pete
     
  8. G3TXQ

    G3TXQ Ham Member QRZ Page

    What if the common-mode path impedance is significantly lower than the impedance looking into one leg of the half-wave dipole?

    And even if only 10% of the current took the common-mode path, do you really want 10% of the antenna current flowing in a wire that's coming back into your shack?

    Steve G3TXQ
     
  9. KC9KHG

    KC9KHG Ham Member QRZ Page

    No,I have inverted V dipoles,with no baluns,and no problems. I have made contacts all over the world with them with 100 watts or less!

    73
     
  10. R3BU

    R3BU Ham Member QRZ Page

    It may happen, having in cables's braid standing wave, that this wave reaches the RIG at it's "0 RF". It is a case of luck..Steve may confirm it.
    But the cable's braid is radiating it's ~10%. And what is more important in a big cityes and even in private houses full of electronics the braid collects to much noise in reseption mode. It is part of total antenna! :)
     
    Last edited: Nov 17, 2009
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