[time-nuts] Traceability after loss of LORAN and WWVB

[Bob Camp]

Hi

On Jun 1, 2013, at 3:34 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:

> 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.

You do the same thing they do. You both watch the same sat(s) and compare to it / them. If you are in the US, you can do common view. There are LOTS of papers on how to do all that. 

Bob


> 
> Cheers,
> Magnus
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