Can I build a 1:4 Current-Mode Balun using only coax?

Discussion in 'Antennas, Feedlines, Towers & Rotors' started by WA7ARK, Sep 16, 2020.

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  1. WA7ARK

    WA7ARK Ham Member QRZ Page

    upload_2020-9-16_10-35-41.png
     
    K0UO likes this.
  2. WR2E

    WR2E Ham Member QRZ Page

    Is this a test?
     
  3. WA7ARK

    WA7ARK Ham Member QRZ Page

    I really want to know...

    The two chunks of coax would be each be operated at a Swr of 2 if using 50Ohm coax???

    Should you use 75 Ohm coax to wind the two chokes????
     
    Last edited: Sep 16, 2020
  4. WR2E

    WR2E Ham Member QRZ Page

    I can't help... other than to say that I wound one a couple years ago on -61 cores with 14ga bifilar wires and it seemed to work OK, no problems noted, did what it was supposed to do.

    No idea what impedance parallel wound teflon insulated 14ga would present, and no VNA to make any measurements with.

    Try it and see!
     
  5. G0KDT

    G0KDT Ham Member QRZ Page

    OK.... And your advice to me on my probs with a bifilar wound 4:1 Guanella balun for an OCF dipole was based set against asking this question Michael :eek:?

    Your diagram is a bit short on windings of coax, as opposed to bifilar, as I've been told at least 6 turns one way then at least 6 the other way on each ferrite ring but the wiring is the same as for a guanella and the 200 ohm resister it what the OCF dipole element load was meant to be (approx.).

    If I am not wrong. I'm sure that the texts I've read said you can use coax to wind baluns so I don't see why not, but then we'd get into all the techie Zo of the wire. So going out of my depth, I then ask do you really mean a balun or a Choke? I say this because the Guanella is, or so I have been told, capable of delivering some common mode choke effect too.

    Phil
     
    Last edited: Sep 16, 2020
  6. WA7ARK

    WA7ARK Ham Member QRZ Page

    Is this version better or worse than the one in post#1?
    upload_2020-9-16_12-27-54.png

    Why?
     
  7. KU3X

    KU3X Ham Member QRZ Page

    Build it. Wait until you see how the SWR is going to climb as you go higher in frequency.
    When I first started and tried to get a good 4 to 1 Guanella Current balun, I could not find the correct telon tubing. The more I experimented, I knew the parallel feeders was the problem. So I tested the feeders to see what the impedance was. It was 114 ohms. Did not make any difference as far as the SWR on 80 meter. I don't remember when the SWR started to climb???.....it may have been around 20 meters. But it's too long along to remember those details. The hunt was on for the proper teflon tubing. Once I got it and learned that the lead length and spacing for input and output leads of the balun had an influence, I was able to achieve a perfect 1 to 1 match right up to 10 meters and beyond.
    You posted a picture of a web site showing how to space the wires for 100 ohms. Many years ago I gave my grandson, a wiz at writing software, the formula for transmission line impedance and told him to make a program so I can plug in the numbers and get the answer. Once he made it easy for me, it was duck soup from that point on.
    Good luck with your project.
    Barry, KU3X

    I forgot, if you use 100 ohm coax you can.

    If this was a trick question.......belay my last !
     
  8. G0KDT

    G0KDT Ham Member QRZ Page

    Well apart from swapping the side (so to speak) of the windings where the crossover link is made in the coax (sheath to center core) I am not sure..... but then I don't profess to know if it is critical for the cross over to be at the dipole element side or if it could be at the feeder side. But on a practicality side of things, it could be V messy to build that cross over with coax even if out of sight in a balun box.
    Phil
     
  9. WA7F

    WA7F Premium Subscriber QRZ Page

    Hang on while I get some popcorn. I want to watch this one unfold. :)
     
    KU3X likes this.
  10. KU3X

    KU3X Ham Member QRZ Page

    Yeh......I got suckered in. Now.......where's the popcorn? It's around here somewhere......
     

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