49:1 Unun

Discussion in 'General Technical Questions and Answers' started by K5LIF, Jan 15, 2022.

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  1. K5LIF

    K5LIF Ham Member QRZ Page

    I have read several articles on winding 49:1 ununs. most I have read show the secondary windings after the pigtail wound consecutively around the toroid. However, I have recently found articles which show half of the secondary on one side, then bridging over to the other side of the toroid to complete the other half of the turns. What is the value of doing this?

    Does it have to do with polarity. As I imagined this geometry on a ferrite rod, it appeared to me as a newbie that the polarity would be reversed.

    Thanks for helping me understand this.
    Clif
     
  2. G0TNU

    G0TNU Ham Member QRZ Page

  3. WA7ARK

    WA7ARK Ham Member QRZ Page

  4. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    Why are some calling these UNUNS?
    These 1:49 transformers are conventional transformers with a primary and a secondary winding with energy transferred via flux linkage thru the core. Like a "Balun" an "Unun" has been in reference to Transmission Line Transformers which transfer energy via a transmission line from input to output.
     
  5. SM0GLD

    SM0GLD Ham Member QRZ Page

    Correct but only for current baluns and unun's
    Any voltage type balun or unun will transfer power via core flux.

    It is a voltage unun.
     
  6. WB2UAQ

    WB2UAQ Ham Member QRZ Page

    The standard 1:4 unun used is a TLT and considered a voltage balun.....no linkage thru the flux that I can see. It is wound as an inverter and the output is taken off the input to the coax and the inverted output of the transmission line doubling the voltage.
     
  7. SM0GLD

    SM0GLD Ham Member QRZ Page

    You are talking about the Ruthroff balun which isn't considered to be an Unun.
    The more common 4:1 unun is wired as a non-inverting transformer but they look very much the same.
    Both use the same type of winding and it might be considered a TLT but at the same time it look like just a bifilar winded transformer.
    I guess it is the way it operates that's makes it a TLT.

    4 to 1 alternatives.jpg
     
  8. W1VT

    W1VT Ham Member QRZ Page

    It is easy to get a wide bandwidth with a bifilar wound 50 to 200 ohm ferrite core transformer because the wires form a 100 ohm transmission line.

    If you want another impedance, say 50 to 12.5 ohms, it is harder to get the optimum 25 ohm transmission line. Two 50 ohm cables in parallel is a possible option.

    Twisting the wires together can lower the impedance, but that increases the chance of wires shorting out. As well as construction errors resulting from wire mis-identification.
     
  9. N8TGQ

    N8TGQ Ham Member QRZ Page

    To get to the other side of the toroid
     
  10. N7EKU

    N7EKU Ham Member QRZ Page

    Cluck cluck
     

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