[time-nuts] Traceable to NIST...??

Bob Camp lists at rtty.us
Mon Jun 28 18:10:26 EDT 2010


Hi

A lot depends on just how much "smarts" is behind the little green light. There's not a lot of information about what they are (or aren't) checking before the light goes green. 

One possibility: 

Check that you have sats in a good constellation for > 24 hours (= check antenna location)
Check C/N on sats stay > 30 db for your constellation (= check feed line and location) 

Check that temperature is stable < 4 C for 24 hours (=  check Rb environment) 
Check the drift rate of the RB is < 1x10^-11 over the 24 hour period (= make sure the Rb isn't broken)
Make sure the lock is stable and the AVAR (or equivalent) looks reasonable (= make sure the loop is working)

Another possibility:

Turn on the green light after we've been locked for > 1 hour (= all must be well if it locked ....)

I'd be a lot more comfortable if I knew that the first set of rules were being used than that the second set. If I actually expected to pass an audit of my setup, then having the basic algorithm information would be needed. 

Bob



On Jun 28, 2010, at 4:57 PM, Michael Baker wrote:

> Hello, Time Nutters--
> 
> Traceable to NIST...? All you need is this LPRO Rb osc being
> disciplined by a GPSDO and you can claim NIST traceability?
> 
> Not the way I understand the rules....
> 
> http://www.tenmhz.com/GPSDO.htm
> 
> What say the list?
> 
> Mike Baker
> ----------------------
> 
> > Today’s communication devices and protocols often require
> > an accurate timebase. Leveraging the best technology of
> > yesterday and today, we are proud to bring you the world's
> > first rubidium GPSDO under $500! The LPRO-101 by Efratom®
> > /Symmetricom®, stabilized by a high-sensitivity GPS system,
> > provides affordable, traceable precision. Watch our DEMO
> 
> * Features: Guaranteed Accurate to < 5x10-11,
> Traceable to NIST when LED is green
> 
> * Typical accuracy is even better → Typical Accuracy Charted
> * Low phase noise 10 MHz, 50Ω BNC output at +7 dBm
> * Includes power supply and high-gain GPS antenna
> * Phase Locked for absolute accuracy over long time intervals
> 
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