2.4 : 1 BALUN

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by K4LRH, May 21, 2015.

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  1. K4LRH

    K4LRH Ham Member QRZ Page

    Anyone ever built a 2.4 : 1 BALUN? Would it be better wound on a toroidal core or PVC tube [air-wound]? The low Impedance input would be a SO-239 - Thanks, Jack, K4LRH
  2. WA7DU

    WA7DU Ham Member QRZ Page

    I have not built one to your specifications. But, curiosity prompts me to ask what you are going to do with such a device. Your writing about a 2.4 to 1 ratio suggests that one objective is resolving an impedance mismatch. That still leaves the question of what source and load you are trying to match. The fact that you specify an SO-239 as the input doesn't clarify what the source impedance might be, because there are coax cables from 50-Ohms to over 900-Ohms (yeah--that would be weird, but it does exist) that would fit the mating PL-259 plug.

    We know nothing about the load or its impedance.

    The fact that you ask about a a device wound on PVC tube makes me think that an objective is supressing common mode current. But, you did not indicate that as a need. "Baluns" comprising a length of coax wound on a PVC tube, or simply coiled randomly do not provide unbalanced-to-balanced conversion, nor will such a device match differing impedances. They do suppress common mode currents, and are more accurately called "chokes."

    To really answer your implicit questions, or even your explicit question, we need an explanation of your objectives.
  3. K4LRH

    K4LRH Ham Member QRZ Page

    Thanks for replying - My concerns are at least three-fold - It appears that the imp. of my 2-element quad will be around 120 ohms - A 1/4 wave Q-section is an unbalanced device that will be feeding a balanced loop [potential common-mode current problem and field strength pattern distorter], plus I've read that it produces a narrower bandwidth - The feed-line will be LMR-400, thus the PL-259/SO-239 combo - A 2.4 : 1 BALUN, if possible to make, would solve all these problems, I believe, Jack; K4LRH
  4. W6OGC

    W6OGC Ham Member QRZ Page

    There is a recent thread about this, "Impedance Matching Transformer" that delved into this. I can't post a link, but a search will turn it up.
  5. W5DXP

    W5DXP Ham Member QRZ Page

    Assuming your quad is a single-band HF antenna, a conventional transformer using #2 powdered iron would be my choice for the balun function. The reactance of the secondary winding would need to be at least 600 ohms.
  6. W1VT

    W1VT Ham Member QRZ Page

  7. NL7W

    NL7W Premium Subscriber QRZ Page

  8. E73M

    E73M Ham Member QRZ Page

    Forget the transformer 2.4:1 on Iron core #2, it is waste of time and will not work over wider range of frequencies.
    You need 2.25:1 UNUN on Ferrite core.

    73 Danny, N4EXA aka E73M

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