On 06/01/2013 09:02 PM, Scott McGrath wrote:
True
However with LORAN and to a lesser extent WWVB traceability process was
well/known and documented and had been in place for decades and was easy to
implement correctly With GPS not so much especially with S/A. Supposedly
the new satellites don't have S/A but since the GPS satellites are primarily
military in nature how will precise positioning be denied in emergency
situations. Shut down L1?, dither the signal ???? Or is S/A still there and
how does a T/F user respond to GPS not running normally???
A colleague of mine runs a cal lab. Guy is a wizard with physical and
electrical standards
I run some of my gear there in exchange for calibration of my instruments as
lab has temp / pressure / humidity controls for physical standards so we both
benefit.
Since the demise of LORAN and WWVB (although d-PSKer may allow us to bring
spectracoms and 117a's back.
To achieve traceability we have been shipping our CS and some Rb standards
under power to labs who have achieved traceability
This is is a pain to say the least. The procedures currently are not well
documented on achieving traceability in the age of GPS only.
And it's also true that most people confuse traceability with adjustment. In
reality it's more of a chain of data with documented values all the way back to
NIST or other national standards lab
NIST offers a calibration service which gives time and frequency
calibration to NIST using common view GPS. Essentially that's a box
being placed at the location you feed with your local signals and the
box will communicate back to NIST and create the calibration records.
The pieces in this, isn't all that magic and esoteric, but put together
in good way and with routines to put it all together.
How to do it properly when getting the NIST service is much more
fuzzier. I have not seen a description of how it should be done, but it
should be possible to achieve in principle.
Cheers,
Magnus
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