Dear all, I recently acquired a 53131A counter and upgraded it with an OXCO timebase. I decided to test it out a bit to see what results I could be expecting from it.
So I hooked up two of my DiY GPSDOs to hopefully get some actual data instead of running DAC value series through MDEV and wondering what the graphs might mean in real-world terms. I chose a fairly simple setup, just logging frequency data with a 2 second gate time as this would give me another digit of output. For lack of a better option, I decided to use the internal timebase of the counter, which is now a used MV89A OCXO I bought on Ebay. Attached find the resulting MDEV graphs. It looks like I can actually "see" the "BBB GPSDO", which is a GPSDO cape I'm currently developing for the Beaglebone Black. It's equipped with an ebay'd MV85A OCXO and a Ublox M8T. The second trace is my Rb-GPSDO which uses a LPRO-101 as the LO. I think I can safely say that this one is down in the measurement noise. Only beyond the 1000s mark it might be visible, but this is also the point where the drift of the counters timebase starts to dominate the graph. At best this graph can serve as a baseline for the counter. Both traces have frequency offset and linear drift removed. BR, Matthias
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