Re: [time-nuts] Holdover: Z3801A vs KS-24361
Hi There isn’t much you can really see on a GPSDO comparing it to a normal OCXO. The OCXO simply is not accurate enough. You need something like a Cs standard, a different GPSDO, or a good Rb for the reference. (Yes, if you have a hydrogen maser, you *can* use that ….). First thing to check is the DAC readings on the unit …. Bob > On Apr 15, 2018, at 6:59 AM, Hal Murray wrote: > > > kb...@n1k.org said: >>> A KS-24361 says: >>> Predict 394.1 us/initial 24 hrs >> That would suggest the unit is unlocked. It should be below 10 us. Just as >> with the 3801, the estimate is a bit fuzzy. You should be able to see issues >> in the data on the Z3809/Z3810. > > It says it is locked and has been locked for days. >>> Locked to GPS TFOM 3 FFOM 0 > > I used this as a learning exercise for my new TICC. Something is clearly > fishy. > > The reference for the TICC is the crystal in a HP 5334B with the good-crystal > option. It's not calibrated, but there isn't any GPS logic to jerk it > around. I assume the swing is due to temperature. I corrected the slope of > the graph by hand. > > Here is a day+ of data: > http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS.png > > Here is a zoomed in chunk: > http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS-2.png > > > -- > These are my opinions. I hate spam. > > > ___ 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.
Re: [time-nuts] Holdover: Z3801A vs KS-24361
kb...@n1k.org said: >> A KS-24361 says: >> Predict 394.1 us/initial 24 hrs > That would suggest the unit is unlocked. It should be below 10 us. Just as > with the 3801, the estimate is a bit fuzzy. You should be able to see issues > in the data on the Z3809/Z3810. It says it is locked and has been locked for days. >> Locked to GPS TFOM 3 FFOM 0 I used this as a learning exercise for my new TICC. Something is clearly fishy. The reference for the TICC is the crystal in a HP 5334B with the good-crystal option. It's not calibrated, but there isn't any GPS logic to jerk it around. I assume the swing is due to temperature. I corrected the slope of the graph by hand. Here is a day+ of data: http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS.png Here is a zoomed in chunk: http://users.megapathdsl.net/~hmurray/time-nuts/TICC/TICC-KS-2.png -- These are my opinions. I hate spam. ___ 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.
[time-nuts] Holdover: Z3801A vs KS-24361
SS is signal strength. CN is carrier to noise ratio. They basically indicate the same thing, but their scale may be different. You can't compare the absolute magnitude of the values from different types of receivers, only do relative comparisons. Other receivers can report dBc, etc. And Trimble devices can report AMU (amplitude measurement units). Some Trimble devices don't support dBc readings. By switching a Tbolt between AMU and dBc, I worked out a table that Lady Heather uses to convert AMU to dBc to that those devices can display the more common dBc values. On the Trimble devices you set the signal level mask in AMUs. --- > the Satellite Status area has a header of SS on the Z3801A and C/N on the KS ___ 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.
Re: [time-nuts] Holdover: Z3801A vs KS-24361
Hi > On Apr 12, 2018, at 1:30 AM, Hal Murray wrote: > > On that Status page, A Z3801A says: > Predict 2.5 us/initial 24 hrs That sounds about right for a 3801. The prediction is something better than a wild guess and not what one would call a solid number. > > A KS-24361 says: > Predict 394.1 us/initial 24 hrs That would suggest the unit is unlocked. It should be below 10 us. Just as with the 3801, the estimate is a bit fuzzy. You should be able to see issues in the data on the Z3809/Z3810. A prediction of < 1 can pop up on occasion, on either unit. More typical estimates are in the “couple of us” range. If you yank the antenna, it still does a respectable ~5 us / 24 hrs or so either way. > > Both have been running for weeks. > > Is anybody seeing similar? no > > > Also, the Satellite Status area has a header of SS on the Z3801A and C/N on > the KS. Does anybody know the units and/or what that is actually measuring? There are tables that translate the Motorola (and some of the other brands) status numbers into rough dbc/ Hz. I would not count on the numbers on a 20+ year old design lining up directly with the latest and greatest modern module. Apparently the SNR calculations are a bit weird. Bob > > -- > These are my opinions. I hate spam. > > > > ___ > 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. ___ 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.
[time-nuts] Holdover: Z3801A vs KS-24361
On that Status page, A Z3801A says: Predict 2.5 us/initial 24 hrs A KS-24361 says: Predict 394.1 us/initial 24 hrs Both have been running for weeks. Is anybody seeing similar? Also, the Satellite Status area has a header of SS on the Z3801A and C/N on the KS. Does anybody know the units and/or what that is actually measuring? -- These are my opinions. I hate spam. ___ 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.