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Thread: PA8W doppler RDF Mk3 up and running

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  1. #1
    Join Date
    May 2009
    Beuningen, about 80km southeast of amsterdam

    Default PA8W doppler RDF Mk3 up and running

    Hello Homebrewers,

    I've got the new Mk3 pseudo doppler radio direction finder with 8-antenna array up and running now for a few days.
    Works like a charm already, but I will extensively test and tweak the device before I publish the schematic diagram on my website.

    The Mk3 has a 32 LED pelorus plus a +5,6 degrees LED, so display resolution is 5,6 degrees.
    Attached to the computer the system accuracy will be around 2 degrees.

    It has a soft switched 8-element dipole array, and one coax cable only.
    (supply voltage and sync signal all running via the single coax)

    I've got preliminary data posted on my website:

    Wil, PA8W

  2. #2
    Join Date
    Jan 2002
    harms way


    Really neat, going to market a kit??
    now with true viterbi decoder!

  3. #3


    Very interesting and easy to build project (since you have done all the hard work of design and optimization!) I look forward to building one.

    Thank you for the effort you put into this project.

    73, Jim WB5WPA

  4. #4
    Join Date
    Jan 2008
    St. Mary's County Md since 2000


    Great progress, Wil. Merry Xmas.


  5. #5
    Join Date
    May 2009
    Beuningen, about 80km southeast of amsterdam


    To N0SYA:

    No, this MK3 version will not be offered as a kit.
    I've just published the schematic diagrammes but that's how far I will go.
    The MK2 version however is much easier to homebrew and I've put extensive documentation on the website about this version.
    It has been built by numerous Hams and I've been sending off PCB's to North America and Australia as well.

    The MK2 pa8w doppler RDF is much more accurate and much more sensitive than most of the hobby-dopplers like the Raneoke design.
    Most of them use hard-switching, which is simple but killing for good results on weak signals, and immunity to strong signals nearby.
    Even the latest versions with microcontrollers and fancy displays hold on to the horrible hard-switching method.
    That's why a doppler doesn't have a very good reputation amongst Hams...

    And additionally I've optimized the antenna arrays itself, which contributed to highly improved performance.
    It can get a good bearing within 10 degrees or so on noisy FM signals that are just too weak to copy.
    For the MK3 version that's within 5 degrees. (measured real life mean accuracy = 3.25 degrees @8m array height)

    Wil, PA8W

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