Posts by DL5ZBS

    I just have tested my setup of Pluto with Leo Bodnar GPSDO and everything is working fine now and I had some nice contacts via QO-100.

    The shift I was talking about was a shift between Rx and Tx in SDR-Console when both windows were synchronized and show the downlink frequency. Before I changed the setting for reference correction the CW-beacon was at 10.489,495 MHz and rx and tx frequency were not tranceive. My signals were approx. 11 kHz beside expected downlink frequency.

    Now beacon is at 10.489,500 MHz and Tx and Rx are working transceive.

    Thus, my conclusion is:

    - There was a correction set for external reference in my Pluto.
    - "fw_setenv xo_correction 40000000" changes it to 40 MHz

    - everything is perfect now.

    Thanks again Detlev and Adrian you have been of great help in this matter.


    Hi Detlev and Ardian,

    Thanks for your comments.
    It seems to me that I should explain my situation a little more detailed.

    - both cpu are acitve => "fw_setenv maxcups"

    - external reference is activated "fw_setenv refclk_source external"

    - external gpsdo is connected running on 40 MHz

    Using Pluto on QO-100 I realised that there is a shift of approx. 11 kHz between Rx and Tx. Thus, I assumed that there is a correction set for external reference. Due to this I checked this parameter with the following command I found elsewhere in the net

    "cat /proc/device-tree/clocks/clock@0/clock-frequency | xxd"

    => it returns the clock frequency as hexadecimal number and tells in my case that frequency is set to "39999716" which could explain the shift when feeding the Pluto with exactly 40 MHz.

    Therefore I tried to set it to 40 MHz using "fw_setenv xo_correction 40000000"

    After this I checked again with "cat /proc/device-tree/clocks/clock@0/clock-frequency | xxd" which still returned "39999716"

    Now I tried "fw_printenv | grep correction" Adrian mentioned and Pluto returned "40000000"

    Maybe everything is fine now. I tell more as soon as I have tested.

    73 and thanks again for your help.

    Happy Easter,


    Btw. I checked "" before but honestly it is not that easy to understand for newcomers.

    If your reference is not perfect you can correct it with:

    fw_setenv xo_correction 39999750 // for example

    Hi Sandor,

    Setting a correction for my external reference is not working. I tried it several times and always did a reboot. I want to set it to 40000000 but it stays with 39999716.

    Any idea what I did wrong?

    Thanks for your help


    Hi Sandor,

    Thanks for the details how to use an external reference. This is exactly what I am looking for.

    73 and hope to meet you on QO-100


    After DJ5PW mentioned to have Rev. D I checked my Pluto again.
    On the lable at the enclosure back side Rev. C is written but on the board Rev. D which I did't noticed so far.

    Obviously we have hardware Rev. D but with current firmware it is called Rev. C.

    I hope that documentation will be published soon.

    Below are two photos of a little higher resolution which may help those of us who have more experience in this matter.

    73 Ansgar

    Hallo Frank,

    ich habe meinen Pluto bei Digi-Key gekauft.
    Wie gesagt, habe bisher keinerlei Dokumentation finden können. Auf dem TCXO steht 40.0 und S 0F. Mehr kann ich nicht erkennen, bin allerdings auch kein Spezialist ins solchen Dingen, ehr ein "Nachbauer"

    73, Ansgar

    I recently bought an Adalm-Pluto, the GPSDO of Leo Bodnar, studied all notes regarding modification and was surprised that my Pluto is looking totally different from what I have seen so far. To make a long story short, I got revision C and unfortunately, I could not find any documentation in the internet. Difference is that TCXO is on the secondary side of the board and that four small connector sockets (IPX?) are on the primary side. One of them is marked as “CLK_IN 3V3 Max” another as “CLK_OUT”. It seems to me that no further modification is needed to feed in the signal of an external GPSDO but I am not sure.

    - Does anybody already has modified Rev C for QO-100 use?

    - How to feed in the signal of my GPSDO?

    - Anything else I have to consider or take care about?

    Thanks for your help and comments,

    73 Ansgar, dl5zbs