[time-nuts] Oops - wrong URL for tvb plot!

SAIDJACK at aol.com SAIDJACK at aol.com
Tue Apr 10 19:37:56 EDT 2007


 
In a message dated 4/10/2007 14:48:34 Pacific Daylight Time,  
tvb at LeapSecond.com writes:

with a  53132A against a good atomic house standard. You'll
see a large phase  offset (many microseconds), a frequency
offset (about +3e-12 or -3e-13).  No, I didn't remove frequency
drift (if any) from the data before I plotted  it.



Hi Tom,
 
how do you best compare an atomic standard against an OCXO on the  53132A?

I did it with the 1PPS inputs (that works, but gives only one sample  point 
per second).
 
Inputting 10MHz and doing T1 to T2 intervall measurements also works  
somewhat, except using the internal gate delay is not perfect, I get  aliasing (there 
is some 100ns offset sometimes - which is random).
 
It works best (no aliasing) when I let the counter free-run without any  
gate-delay, but then I do not know the sample Tau of my data.
 
That's partially because I am using the serial port output at 19200 Baud,  
and I think the counter is spitting data at me as fast as it can (limited  by 
the RS232 port). Seems its about 15-20 measurements per second free  running.
 
I am thinking that maybe I should provide a 100ms external gate input etc,  
at least that way I will know for sure that my Tau is 0.1s and I get 10x more  
data than simply comparing the 1PPS outputs.
 
Lastly, I have the High Stability time base, but have still been using an  
external Cs reference to feed 10MHz into the counter. I wonder if the internal  
time base is better (probably less short term ADEV than the Cs) for these 
short  time intervall measurements.
 
Any hints are appreciated,
Thanks,
Said



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