Design of Crystal filter

Discussion in 'Homebrew and Kit Projects' started by VU3KFK, Aug 3, 2021.

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  1. VU3KFK

    VU3KFK Ham Member QRZ Page

    Hi,

    I have sorted out crystals according to their frequency and made a MS excel document. I user G3UUR method (details to this link https://kk9jef.wordpress.com/2016/04/25/g3uur-crystal-oscillator/) to measure the crystals. I have currently no experience of making crystal filter. Can anyone help me to make few filters. I am uploading the measurement here. There are 5 groups. 3 groups for CW filter using 3 crystal each and 2 group for SSB filter using 4 crystals each. upload_2021-8-3_20-29-44.png upload_2021-8-3_20-30-14.png upload_2021-8-3_20-31-1.png upload_2021-8-3_20-31-39.png upload_2021-8-3_20-32-6.png
     
  2. KX4OM

    KX4OM Ham Member QRZ Page

    From the article that you linked, you need to calculate one of the motional parameters, Cm or Lm. This parameter, along with the holder capacitance and the 3 dB bandwith can be entered into the crystal filter design program Dishal. I have also used other software, including AADE Filter Design and W7ZOI's XLad08 program, but I think Dishal is somewhat simpler to use for for first-time design. Refer to this article:

    sq2gxo.wordpress.com/2010/04/05/crystal-ladder-filters-i-software/

    The simplest crystal filter design is the Cohn min-loss, where the values of the capacitors are all the same. Dishal includes a module for Cohn filters. These filters are good for 3-pole CW and simple 4-pole SSB filters. Dishal also can calculate Chebychev filters, which are more complex, and typically can be used for 5, 6, or 8-pole SSB filters with steep skirts.

    This website has a download link for Dishal2052, the most recent version:

    warc.org.uk/?page_id=387

    Also, download the help file, dishalhelp from the same site.

    Ted, KX4OM
     
    VU3KFK, VE2GCE and N7EKU like this.
  3. VU3KFK

    VU3KFK Ham Member QRZ Page

    Hi Ted,

    Thanks a lot for pointing me to the right direction. I think found all the resources that I need to build the filter.

    Regards
    Ashok, VU3KFK
     

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