[time-nuts] Holdover: Z3801A vs KS-24361

Bob kb8tq kb8tq at n1k.org
Sun Apr 15 10:01:37 EDT 2018


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 <hmurray at megapathdsl.net> wrote:
> 
> 
> kb8tq at 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.
> 
> 
> 




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