Rough sounding audio

  • Hello

    Am newly qrv on satellite. Everything works. Using Pluto. GPS controlled 10MHz reference, 25MHz and 40MHz phase locked loops for LNB and Pluto. Console software.

    However, there is a slight warble on the audio, especially noticeable on cw,

    Looks to me like a 50Hz FM modulation. No amount of notching or low pass filtering makes any difference. If I look at the audio waterfall in fl digi, two lines can be seen to each side of the signal, about 50Hz apart. This audio comes straight out of the computer like that.

    If it is mains hum, where does it come from? All power supplies are switchers, so no 50Hz from them. Has anybody had a similar problem?



  • Hi Frank, a very welcome to this forum and congrats on succesfully setting up your QO-100 station.

    Just a thought on your question: Maybe there is interference from the USB-cable between Pluto and PC/laptop?. A ferrite will improve this.

    Simon Brown has a note on this subject...

    73 Ed PA1EW

  • i2NDT Hi Claudio, I should have mentioned that the drawing is not mine, but info by PA1AIS. So, just passing info that seems relevant, I have found on the web.
    I would suggest using two (small value) capacitors for each signal & ground connection, blocking DC and low freq interference. The ground connection in the Pluto outputs will be isolated in this way. When others have a better suggestion, please let us know!

    My Pluto has arrived and needs to be set up in a portable system that I have planned.

    73 Ed