Query: Conversion of Ganged Johnson Variable Capacitor to Differential Type

Discussion in 'Ham Radio Discussions' started by K5HU, Nov 18, 2021.

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  1. W9WQA

    W9WQA Ham Member QRZ Page

    these help?
     

    Attached Files:

  2. W6EM

    W6EM Ham Member QRZ Page

    Late to the 'party,' but why give up the innate ability of a T network to match a wide range of impedances by forcing input and output arms to be the same value? In other words, by using a differential capacitor, you lose the ability to match significantly different tuner output impedances unless you can independently adjust input and output capacitors......or am I missing something?
     
  3. WN1MB

    WN1MB Ham Member QRZ Page

    Better late than never.

    I suspect some are willing to sacrifice tuning range for the "convenience" of having only two controls to adjust - one L, one C.
     
  4. K5HU

    K5HU Ham Member QRZ Page

    Thanks to Donald K4KYV for providing a detailed method of modifying a Johnson variable capacitor. His discussion nailed the method that I was hoping to hear about. Thanks to everyone else for the variety of good ireas. I'm still open to more discussion on this subject, so please keep the potential solutions flowing in. 73, Bill K5HU
     
    KA4DPO likes this.
  5. W6EM

    W6EM Ham Member QRZ Page

    Quite a sacrifice. Zin = Zout equates to a symmetrical network. Is the antenna Z going to always be the same as the transmitter Z?
     
  6. K5HU

    K5HU Ham Member QRZ Page


    Thanks Donald K4KYV for providing a detailed method of modifying a Johnson variable capacitor. Your discussion nailed the method that I was hoping to hear about. Thanks to everyone else for the variety of good ireas. I'm still open to more discussion on this subject, so please keep the potential solutions flowing in. 73, Bill K5HU
     
    N2EY likes this.

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