I like that explanation. I think I get it. I don't think it is likely to cause me any worry.
My actual measurement of ADEV on my VE2ZAZ device gave me a 100,000s sigma of just under 1E-10 and that works for me (best is at 1000s, 4E-11). Maybe the strength and the danger of the VE2ZAZ design is the wide range of integration settings. If I were to pick some very unfortunate settings, maybe it would degrade overall performance in the way you describe. Thanks for taking the time to explain it to me. Chris On 6/13/2013 10:15 PM, Richard H McCorkle wrote: > Chis, > > Over time without phase correction the analogy would be more like > zig to the right, correct to go straight, zig to the right, correct > again, and keep repeating this sequence ad infinium as the source > ages in predominantly one direction. Each time the phase shifts in > the same direction and before long you are on a different road a > full clock cycle to the right and continuing to shift in the same > direction. The total number of clocks over the period has changed > from the ideal even though the average frequency has been correct. > So over the short-term the right number of cycles occur, but over > the long term there is an increasing error from the ideal number > of clock cycles as the period increases. > If all you need is a frequency that is stable over short periods > then the phase is of no concern. But when using a scope or TIC to > compare a device under test (DUT) to the reference to determine its > Adev over longer periods then you need the phase of the reference > to be constant over the maximum measurement period (typically 4-5 > days for a 1-day Adev value) to determine the DUT long-term drift. > By keeping track of the total accumulated count from an arbitrary > starting point (i.e. when the reference sample is taken) and adding > 6800 HEX each update the reference count would represent the ideal > count after X updates if no drift had occurred. Comparing the > current count to this ideal gives the total change since the > arbitrary reference was first stored. By adding steering to keep > the actual sample count at the ideal value then over the long-term > there would be no drift as it would be corrected out. The actual > phase to GPS isn't the important factor - the change in the phase > over long periods (like a day or week) is as it represents an error > in the total number of counts over that period and a reduction in > the long-term stability. > > Richard > > >> >> I'm with Bob in that I don't really understand this description. >> >> And what are we trying to be in phase with? the 1PPS? >> Is it possible to reproduce the actual phase of the >> clock in the GPS birds once it has been through my GPS >> and come out as 1PPS? >> >> I picture the EFC steering the car straight down the road. >> And you want to adjust not just the drift to the right but >> steer back to the center of the lane. I think I get >> that part. I don't get who is setting the lane >> and why I should care. >> >> Do the statistics (ADEV, etc.) show that this is an improvement? >> If I'm doing my slow zigzag down the center line or the >> right shoulder, again, do I care? >> >> Chris >> w0ep >> >> >> _______________________________________________ >> 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.
