> According to Wikipedia, this is insensitive to drift and so seems like > a better tool for measuring oscillators, like ocxo. I don't think I've > seen this being used by anyone on the list and wonder why?
Hi Steve, I use it sometimes when I need to. But note that in most cases you do NOT want to ignore drift. If you measure an OCXO for the purpose of using it in a clock or appliance or radio or test equipment you really do want to know if it has drift or not. ADEV will show this, while HDEV will not. So you have to be careful about using statistics that deliberately and quietly ignore effects that may be important to your application. On the other hand, if you are choosing an OCXO to be used in a smart GPSDO which you know has internal adaptive drift rate calculation and compensation then, yes, HDEV would be a more appropriate statistic than ADEV. But before you run off and use HDEV for everything note that the other practice that is far more common -- simply remove frequency drift from the raw data before computing an ADEV on the residuals. If you look at plots in professional journals you will often find comments to the effect that phase, frequency, or drift offsets have been added or removed prior to making said phase, frequency, or stability plots. Here, to see the difference that HDEV makes (or not) see: http://www.leapsecond.com/pages/hdev The command line program that I use (ADEV3) these days: Tool for ADEV, MDEV, HDEV: http://www.leapsecond.com/tools/adev3.exe Source code (compiles in windows, bsd, or linux) http://www.leapsecond.com/tools/adev3.c /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
