[time-nuts] GPS and national standards in frequency

[Marco A. Ferra]

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