[time-nuts] GPS and national standards in frequency

Mike S mikes at flatsurface.com
Tue Mar 25 01:52:33 UTC 2008


You might want to read this: http://tf.nist.gov/service/gpscal.htm

At 09:27 PM 3/24/2008, Marco A. Ferra wrote...
>Dear time-nuts
>
>My name is Marco Ferra.  I'm doing research on an electrical metrology
>laboratory in Portugal, and I'm conducting a study on how to establish
>tracebility to frequency using one (or more) GPSDO's.  I came across
>febo.com's site and this mailing list after searching the net.  Let me
>tell you what I'm doing.
>
>I have put side-by-side two GPS receivers, one HP58503 (now owned by
>Symmetricom I believe) and a Fluke 910R, both with it's own antenna.
>Both antennas are separated by about 100 meters.  I'm tracking the 10
>MHz output of both GPS receivers with a Fluke PM6681R Counter.  I'm
>using the internal Rubidium oscillator of the counter and using 
>channels
>A and B for the measurements.  Each 10 seconds, I'm recording the
>frequency on channel A, B, and the phase (in degrees) between the two
>signals.  I have resolution on the phase by 1/10th of degree.
>
>With the phase, I can get the time differente in nano-seconds between
>the two signals:
>
>=phase(degress)/(360*10000000)*10^9
>
>I'm putting 10000000 Hz has a nominal frequency for the calculation, 
>I'm
>not sure if should use the frequency recorded on channel A or B.
>
>Then I calculate the time difference, the TIE (ns), the Delta Tie (ns)
>accumulative, and then the Delta f (it's equal to Delta TIE (ACC) /
>measurement time (could be 10, 20, 30 secs)).  Please take a grasp at
>page 4 of
>http://www.pendulum-instruments.com/Assets/download/accurate_calibration
>_article.pdf
>
>Given these two GPSDO's, and given the very small Delta f, I can 
>assume
>that both GPSDO's are functioning proprely (could I indeed?).  But I'm
>not sure how I can get tracebility to national standards, to NIST, for
>example, on the 10 MHz output frequency.  Perhaps it's difficult, but 
>I
>need a solid proof that my 10 MHz output is traceble to a primary
>laboratory.
>
>I have seen that you all have a vast experience in this area, and
>perhaps we could work together to gather good results and achive this
>goal.
>
>Sincere regards, and thank you for reading,
>Marco
>
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