Hello, If I look on the one hour plot it look like it goes in hold mode due to zero used satellites. If my assumption that the light blue graph in the bottom is satellites it sees no satellites during about a minute and after that it selects a fast time constant. From the TIC offset and DAC changes, a time constant of 10-20 secs seems reasonable if it is a PI-loop with a low pass filter on the TIC value.
So nothing strange except the jump of the DAC value in hold mode. As always you really want to know what the firmware does. As the satellite constellation is the same every 23h56min I guess it could be zero usable satellites every day at about 8am for several days. Lars Från: Skip Withrow<mailto:skip.with...@gmail.com> Skickat: den 4 oktober 2017 03:17 Till: time-nuts<mailto:time-nuts@febo.com> Ämne: [time-nuts] Weird GPSDO behavior - update Hello Time-Nuts, Well, I think I know a little more about my GPSDO problem, but probably have more questions now than before. Thanks for all the replies to the first post with thoughts and suggestions. I first tried restarting Lady Heather and doing a cold boot on the NTGS50AA (then entering the same disciplining values). Same behavior. I let it run over the weekend and the same behavior happened on Saturday and Sunday morning. So, yesterday (Monday morning) I changed the gain to the gain of the oscillator (.0072Hz/V), damping to 1.2, and time constant to 900s. On the attached PRS10-2 plot you can see that it quickly settled. This morning, it looks like all is well from the plot (about an hour before the furnace kicks in at the right of the plot). HOWEVER, when the plot is expanded there is still funny business going on with the DAC control voltage at the same time of day. I just think the changed parameters limit the disturbance. The expanded plot is the attached PRS10-1. At this point I'm beginning to think that the NTGS50AA is the issue, but there are lots of questions left. 1. There are various version of the NTBW50AA/NTGS50AA GPS/operating firmware. Mine is 10.3 and I notice that it has the LH 'ro' designation (as does the 10.4 version). The 10.5 version does not give the LH ro notice. Maybe it behaves better with the disciplining? I will have to give a 10.5 a try. 2. Why does the glitch occur at 8am in the morning? Will have to try powering the NTGS50AA up at different times and see it the glitch moves around. 3. Which disciplining parameters are affected by this glitch and which are not? 4. Have other people seen this same behavior? Does it happen on Thunderbolts too? I'll update again when I have more data. Regards, Skip Withrow _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
