[time-nuts] GPS and national standards in frequency

[Marco A. Ferra]

Thanks Mike, I'll give it a close look.

Sincere regards,
Marco 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On Behalf Of Mike S
Sent: terça-feira, 25 de Março de 2008 1:53
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS and national standards in frequency

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_calibratio
>n
>_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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