Q-factor measurements of different LW-Antennas

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  • Опубликовано: 10 дек 2024

Комментарии • 18

  • @jerryuhte1284
    @jerryuhte1284 2 года назад

    Excellent video and info , makes a little more sense for me ! Thanks !

  • @aerofart
    @aerofart Год назад

    Another great video. Question: does your measurement setup compromise the accuracy of the results due to the antenna location breaking the 1meter proximity rule you spoke of in previous videos? I imagine it does but that the effects at relatively low frequencies must be slight.

  • @ssubaihi
    @ssubaihi 7 лет назад +1

    أختبار ثوري ، يستحق جائزة

  • @AdityaMehendale
    @AdityaMehendale 7 лет назад +2

    Hi Roger, have you done another video explaining the origin of the x5 multiplier to convert cycles to Q-factor? (For my own calculations, I use pi *1.44 which gives a factor x4.5).

    • @KainkaLabs
      @KainkaLabs  7 лет назад +1

      In this video the method is introduced:
      ruclips.net/video/gJlkWt3VYxM/видео.html
      From my memory the factor of 5 of results from e^(-0.5)*pi = 5,18
      The general formula should be Q = n(x) * pi * e^(-x)
      where n(x) is the number of cycles at a point x, where x is the fraction of amplitude relative to a reference amplitude (e.g. the maximum amplitude)

    • @AdityaMehendale
      @AdityaMehendale 7 лет назад

      Hi Roger,
      If you express exponential decay of a variable U(t) as:
      U(t) = U(0)*e^(-t/tau)
      where tau is the time-constant at which the variable decays to 1/e of its initial value, then the time it takes to decay to half its value is:
      t(half) = tau * (-ln(0.5)) = 0.693 * tau
      In other words, if you *measure* the half-life as t(half) on an oscilloscope, then
      tau = t(half) * (1/0.693) = 1.44 * t
      Then, if Q-factor is defined as _"Pi times nCycles in one decay-time-constant tau"_ then it may be calculated as n*1.44* Pi, i.e. about a factor 4.53*n (where n is the nCycles in one half-life)
      One of us is making a mistake ;)
      Did you see the FEMM model, btw?
      Cheers!

    • @KainkaLabs
      @KainkaLabs  7 лет назад +1

      You might be right. I haven´t the book at hand and where I got the factor 5 from.
      Anyway we are both less than 10% off from the rounded value of 5.
      And the slightly "better" Q-values that result from multiplying by 5 instead of 4.5 compensate for the non-negligible loading of the tank-circuit with the 10MOhm resistors.
      During the measurements I recognized a strange effect that there is a big difference if I use 1 MOhm coupling-resistors or 10 MOhms. That shouldn´t be the case because the calculated resonance-resistances are in the range of 100 kOhms.
      I still have to make a comparison with 100 MOhm coupling-resistors to see if 10 MOhms is really enough.
      And yes I got your email with the FEMM-file.
      Still have to find the time to work myself through the software :-)

    • @wd8dsb
      @wd8dsb 4 года назад

      Hi Aditya, you are correct that the factor is 4.5 and it's easy to confirm this using a simple LTSpice or similar model.

    • @AdityaMehendale
      @AdityaMehendale 4 года назад +1

      @@wd8dsb Cool. Thanks for checking :)

  • @allthegearnoidea6752
    @allthegearnoidea6752 3 года назад

    Great video very interesting thanks

  • @lovelycollection100
    @lovelycollection100 Год назад

    Can you make a video with nanovna q mesure

    • @KainkaLabs
      @KainkaLabs  Год назад

      Yes, if you send me a Nano-VNA.

  • @tonychristoph1063
    @tonychristoph1063 5 лет назад

    hello
    Is the vidéo série about radio and antenas is over ?
    It was so interesting

    • @KainkaLabs
      @KainkaLabs  5 лет назад +1

      No, it ain´t over yet :-) I still have some topics to show (like e.g. mythbusting crystal radios). In the last 6 months I didn´t have time to shoot new videos but I will probably continue in January.

  • @tonychristoph1063
    @tonychristoph1063 7 лет назад

    thank you fpr sharing .. very good vidéo

  • @bundylovess
    @bundylovess 6 лет назад

    Would love a copy of your notes on this good video big thumbs up 👍

    • @KainkaLabs
      @KainkaLabs  6 лет назад +1

      Sorry, but I don´t make notes or a script. It´s all prepared beforehand in my head :-)
      Just freely speaking.

    • @bundylovess
      @bundylovess 6 лет назад

      KainkaLabs thank you for your reply 👍