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KC901S - Save CAL = Write Failed

By WTEK •  2017-03-18 04:52:38 •  333 clicks

When I try to save my user CAL after doing a valid SOL, do I get the message "Write Failed"
I have no problem saving normal measurements to my micro SD.

Are others having this problem ?

Daniel Wahl

message  problem  Failed  having  normal 

5 Reply | until2018-05-26 09:50Add a reply
    WTEK  2017-03-30#1 -Reply


    HI Maximo.

    If you have a 6dB attenuator just ad it directly on to the RF IN port, then perform CAL.
    Now should the KC901 read 0dB IL with 6dB attenuator 2 cables attached.

    After this perform your measurements of the balun again and you will get more correct measurements.

    But the balun is 4:1 = 200:50 so you would have at mismatch when doing S21.
    To test preformance of the balun you should use following setup.

    Mode = S11
    Format = VSWR
    Center frequency = 20MHz
    Span = FullSpan
    SweepPoint = 3150

    Now connect the input/coaxial side of the balun to SOURCE port of the KC901.
    Connect a 200Ohm non inductive resistor to the output/antenna side of the balun.

    Perform measurement.

    Now should you be able to see how close/good the balun is transforming 200Ohm to 50Ohm/1:1
    I would normally expect a result ranging from 1:1 to 1:1.6


    EA1DDO  2017-03-30#2 -Reply

    @WTEK Hi Daniel, from some days I am measurement S21 from a 4:1 Guanella balun. Most values are under normal range but one of them I can´t get it correct.
    The S21 loss from input to output, it is always showing around 6dB loss when it should be around 0dB !!
    Now reading your discover about the insuficient return loss of RF IN... it could be the cause of mine headache !!

    Unfortunatelly, I don´t have any other test equipment to check that.

    WuXiao, please, take some action on this.
    73, Maximo - EA1DDO

    WTEK  2017-03-29#3 -Reply


    I have done som testing
    The fault is not on the TF card but on the KC901S.

    If you start by saving a measurement then the KC901S recognize the TF card and you can afterwords save the calibration.
    If you only try to save a calibration after bootup the file is corrupted.

    Please opdate firmaware!

    Next issue is the insufficient returnloss of the RF IN port wich make the KC901S useless for S21 measurements!

    The VSWR of the RF IN port is abouts 2:1 and therefore do I get funny readings due to mismatch !

    BG8NPK  2017-03-29#4 -Reply

    this issue usually cased by the TF card
    you can format the card agin or change a tf card

    EA1DDO  2017-03-20#5 -Reply

    Hi Daniel,
    I guess the Cal does not write to the SD card, but an internal memory.
    You can try to reset your device.
    73, Maximo - EA1DDO


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