Hi My first guess is that your limiter is (for what ever reason) doing better at say 1 Hz offset than it is at 10 Hz. Second guess would be that the higher offset is closer to a noise source / spur in your lab. Past that, you get into a lot of "that depends" things. If you are doing cross correlation then you may be better correlated at the lower offset....
To directly answer the question - no there nothing about a lower offset that by it's self should improve ADEV, provided the effective measurement bandwidth is not changed. If you change the measurement bandwidth then lower bandwidth means less noise. Since a lot of "modern" gizmos do a post filter on the data, you do see data plots done that way. Simple answer is that it mostly impacts the shortest Tau for "normal" sources. Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mark Spencer Sent: Monday, March 26, 2012 5:07 PM To: [email protected] Subject: [time-nuts] Basic question re adev measurements Greetings, I was reviewing some older adev plots of mine and noticed that there may be a correlation between lower adev numbers and lower frequency off set between the reference source and the device under test. It's my understanding that the adev calculations remove constant frequency off sets but I'm wondering in practice this degrades the the measurements. It occurs to me that if I am comparing two 10 MHz signals with a TIC that the available dynamic range of each measurements will be 100 ns. Would a constant frequency off set effectively reduce the precision of the measurements by eating up some of this dynamic range ? To put this in perspective frequency offsets of say one or two parts per trillion seem to result in better adev readings than off sets of say ten or more parts per trillion. Sorry if I have missed something obvious here. Thanks in advance Mark Spencer Sent from my iPod _______________________________________________ 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. _______________________________________________ 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.
