Posts by DB8DT

  • problems with Pluto Sdr

    Are you using SDR Console and have you tested you set up with other software?


    Because I also had a similar problem with my Pluto some time ago. No output power - but everything worked the day before. The setup was not changed in the meantime.


    First I was worried that my Pluto was damaged. But it turned out that due to a Windows update my USB headset stopped working properly. It seems that if there's no properly working microphone present in the SDR Console no power gets out of the Pluto - even if you tune or do a tone test.

  • Adalm Pluto & GPSDO

    @DO1OHB:

    Details about the input resistance of the SDR chip can be found in the reference manual (-> page 15).

    In short: you can't assume a 50 Ohms load.


    As mentioned in one of my last articles above, you could build a voltage divider (C123/C124) or use an external coax attenuator, as others have suggested.

  • Adalm Pluto & GPSDO

    Here's another possible solution:

    According to the schematic you could also install C124 (which is in the unmodified Pluto not installed) with a value of 18 to 27pF and keep the existing 18pF series capacitor (C123).

    In combination with the capacitance of the XTALN input (approx 10pF) they would form a capacitive voltage divider like this:


    approx. 1.3 to 1.1Vpp @ XTALN


    In case if you would like to reinstall the org. TCXO you only have to remove C124.

  • Umbau Adalm Pluto TCXO

    Got all the things together and was able to do some tests with the 74LVC1G04GV inverter.

    I could achieve an output of about 1.3 Vpp with the following circuit design:




    Now all the problems I had with Pluto after changing the TCXO are gone. No more drift and no spurious signals.


    I have some inverters left just in case someone wants to try this solution.

  • Umbau Adalm Pluto TCXO

    I also have problems that seem to be caused by a 1.8V Abracon TCXO and it's low clock signal. I had an idea similar to PY1SAN, and my plan is to translate the cropped sine wave from the TCXO to a 1.8V CMOS signal.


    After some searching I found an inverter from Nexperia (74LVC1G04GV) and I decided to give it a try. It seems the specs are nearly the same as the one from TI.


    With some luck I will getting tomorrow the ordered parts, and then I can do some tests over the weekend.