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Wavelength and matching components.

Discussion in 'Radio and Wireless' started by Rajinder, Apr 29, 2019.

  1. Rajinder

    Rajinder

    409
    7
    Jan 30, 2016
    Hi all,
    I was trying to find the difference of wavelength of 868MHz compared to 928MHz.
    Using a online calculator i found that the wavelength if 868MHz is 34.5cm and 928MHz is 33cm.
    If i wanted to use a printed antenna, would i simply make the length of the track 33cm? What hapoens to matching components for 50R matchibg, will they change for a 928MHz compared to 868MHz? Finally, please could you explain what quarter wavelength means with resoect to 33cm, is it 33cm/4? Why is this important?
    Thanks in advance.
     
  2. davenn

    davenn Moderator

    13,325
    1,769
    Sep 5, 2009
    34.5 yes 33 no should be 32.3


    no. you never use a full wave antenna plus those figures above don't take into account the velocity factor of the antenna on the board

    matching at the feedpoint is another whole different ball game


    A 3/4 way is the usual length .... yes 34.5 /4 or 32.3 / 4 BUT as I previously said, you still have to find out what the velocity factor will be

    so for an example the Vf = .65 then you will have

    34.5 / 4 = 8.625cm
    then
    8.625 x .65 = 5.60cm as a final tuned length


    because if you do di it like that, it will never tune up on the correct frequency


    time for you to go do some searching and study of PCB antennas ;)


    Dave
     
    Rajinder likes this.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    9,370
    1,904
    Nov 17, 2011
    e.g. these:
     
    Rajinder likes this.
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