Le 4 juin 2012 à 05:43, David I. Emery a écrit : > On Sun, Jun 03, 2012 at 09:20:59AM -0700, J. Forster wrote: >> Is there any indication the carriers of WWVB and MSF are locked together? >> >> -John >> >> ================= > > Given it's only 60 KHz and certainly somewhere north of parts in > 10^13 and probably down to 10^14 or 10^15 the distinction kinda escapes > one. > > They may not be locked to each other, but are so close in > frequency that relative drift would be AWFULLY slow... especially if its > more like 10^15 from primary maser standards... > > There are only 5.184 * 10^9 cycles of 60 KHz in a day after > all... and it takes a while for a error of a few parts in 10^15 to > pile up to one whole cycle... > >From the doc on NIST and NPL sites, we are not in maser country here. The >transmitters frequencies are disciplined by cesium standards. For WWVB the >frequency is kept to a few parts in 10^13 ( NIST Special Publication 423) and >for MSF at 2 parts in 10^12 and are both sync'd to UTC(k). As tvb points out, >the the received signal will be phase shifted according to TOD and atmospheric >conditions. The guys at NPL monitor(ed) the MSF signal to provide(ed) data for >anyone wanting to use it for calibration in monthly bulletins of performance. >I expect NIST do the same for WWVB but have been able to find a ref. Check out ><http://npl.co.uk/upload/pdf/user_guide_bullitins.pdf> and the last bulletin >that the site links point to , for april 2011, ><http://resource.npl.co.uk/time/bulletins/msf/msfbul_04_2011.pdf>. What is >interesting from the MSF data is that the phase offsets are quite significant >where they are received in what I expect are optimal conditions at midday when >ionospheric effects are minimal. I don't know what happened to latter issues >if any. Did they abandon them?
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