QO-100 psk beacon stability?

    Hello there!


    I'm using an Adalm-Pluto-Setup for QO-100 in conjunction with the dual-port Leo Bodnar GPSDO (one out for LNB, one out for Pluto).

    Sometimes I enable the Geo-Beacon display in SDR console just for the heck of it. So, often the display is

    almost a vertical straight line, as one would expect. But sometimes I see quite a zig-zag pattern, and the frequency

    shown, wiggles around 5-15 Hz (+-), within seconds (not the expected shift within 24h's or so). And then, its gone, and I'm back to the almost vertical line.

    Whom to trust? ;) Is it worth chasing down some rabbit hole? I mean, measuring things again, just to be sure, would be not a big deal, but maybe someone on the forum has past experience or insight in that matter... before I carry some test equipment to the terrace to check if everything is still really fine on my side. I'm using SDRC build 2870.


    PS: I read about past known stability issues with the beacon in that matter, but those threads/articles are ~2 years old.


    Many thanks in advance for any input.


    Regards,

    Sebastian

    Hi there,

    I don't know when and why it happens, but i too see some wiggling now and then. My setup is a RTL-Stick and a homemade GPSDO with 25MHz OCXO for the LNB , this rules out your Leo Bodnar and Pluto for the cause. To check for instabilities, listen to the upper tone on the lower cw beacon (or lower tone on the upper beacon) when the beacon transmits a straight tone. If it whines while the vertical line in the Geo-Beacon display zig-zags, you have the proof there is some instability. 5-15Hz whine is easy to hear. This won't tell you where the instability happens, but there is a chance sdr console displays quick changes in frequency that don't exist.

    Maybe mixing with other signals on the satellite? This might have an impact on reception and make the algorithm display weird things resulting in zig-zag. My 2 cents.

    73, Martin

    YMMV

    Hi Martin, many thanks for your answer, your video, and the idea on how to test "against" the cw tone(s).

    My zig-zag-phenomenon just happened again. Now I did what you suggested while that was the case, and guess what: Super-steady cw tones to be heard. So it does not seem to be me, great.


    Greets, Sebastian