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Thread: instruction discrepancy 10 W Amplifier Kit Pacific Antenna: transformer turns ratio

  1. #1

    Default instruction discrepancy 10 W Amplifier Kit Pacific Antenna: transformer turns ratio

    This question is about the turns ratio on the toroid transformers.
    I am building this kit:
    http://www.qrpkits.com/10wamp.html
    and see the instructions here:
    http://www.qrpkits.com/files/10W_HF_AMP20170515.pdf

    this kit has three transformers T1 T2 and T3.
    Instruction page 9 says:
    "14 Turns 4:1 Bifiliar on FT50-61"

    The schematic (page 13) specifically calls out 4:1 on all three.

    The Discrepancy:
    But the picture in the instructions shows 14 turns of red and 14 turns of green wire.
    That is a 1:1 turns ratio.

    I propose:
    Primary to Secondary turns ratio of 4:1, e.g. 12 turns of red wire and 3 turns of green wire.
    Where the 12 turns are on the left side (closer to the the input).

    Would this make sense?

    Thanks,
    John
    AC2SG

  2. #2
    Super Moderator pmh's Avatar
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    It’s correct as shown in the manual, so just wind them as they show.

    There are plenty of websites explaining the theory.

    Kind regards,



    Phil

  3. #3
    Super Moderator 5B4AJB's Avatar
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    Bifilar transformers are double-wound, meaning you thread two wires next to each other to make one turn.

    Imagine you take your winding wire and fold it in half, thread the folded end through 14 times and you have your bifilar wound transformer. Now wind the secondary in the same way with another doubled-up wire...

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