[time-nuts] time-nuts Digest, Vol 43, Issue 35

Pete peterawson at earthlink.net
Thu Feb 14 20:28:27 UTC 2008


Martyn,

I have used a PM6681 with HP105B reference to look at:

1. FS700 (OXCO option) as a "typical" modest quality OXCO
2. An FRS-C Rb as a "low cost" Rb device

Both measured devices were either undisciplined or awaiting
the next application of new EFC; thus I limited the observation
times to 256s. I configured the PM6681 to report frequency,
but it is a TI device which computes frequency readings. Used in
this mode, the PM6681 reports 1mHz p-p range for 256, 1s 
gate time measurements of it's 10MHz Ref output.

The DUT results are:

1. OXCO - 10Mhz w/2.7 - 3.1 mHz p-p range

2. FRS-C - 10Mhz w/4.4 - 4.8 mHz p-p range

Both devices were measured 4 times, which is why the 
results are expressed as ranges.

It appears that your Rb is much better than my FRS-C,
and your OXCO is worse than mine. It would be helpful
to see a few other sets of measurements.

Pete Rawson




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