[time-nuts] Second FTS4060 shows Drift, is it me?

Brooke Clarke brooke at pacific.net
Mon Feb 6 13:04:32 EST 2006


Hi:

A year ago I took apart the FTS4060 that was DOA (s/n 1013) because of 
rough shipping and used it to figure out most of the interconnect 
wiring.  A few months ago I put it back together with the thought of 
selling it as a parts unit.  But first powered it up and found that it 
now locked and seemed to be working so tried to set the C-field. 

For the last couple of weeks it has shown a parabolic plot like s/n 
1227, although this time the polarity is opposite that of s/n 1227 which 
also showed drift, but that may be a setup difference.  A plot of s/n 
1227 is at:   file:///C:/Webdocs/pdf/Cs_Drift0429.pdf 
The equation for s/n 1013 is:
 y = 2.7943x2 - 302.64x + 8969.4 and the quality of fit is
R2 = 0.9088.  The x-axis is in days and the y-axis is in ns. 
The first derivative of the equation has a first term of 2 * 2.7943 * x 
ns/day or +5.3E-14 seconds/seconds drift rate.
Today's plot is at:   file:///C:/Webdocs/pdf/sn1013_850_Drift2.pdf

The current setup is:
SR620 time interval counter doing 500 averages (500 seconds = 8 1/3 
minutes).  
Start from Motorola M12+T (9 ns jitter).
Stop from FTS4060 1 MHz output.
Manually enter into spreadsheet date and time of reading (usually not on 
the 8 1/3 minute change, just a random time) and counter value.

For most of the test the SR620 was using it's internal oscillator and 
just recently I changed it to the PRS10 external standard but that does 
not seem to have made any difference.

Is there something I'm doing wrong that would cause apparent drift? 

Thanks for any thoughts,

Brooke Clarke, N6GCE

-- 
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