[time-nuts] ANN: UK MSF 60 kHz interruption, 2012 June 14
michael.cook at sfr.fr
Mon Jun 4 07:35:20 UTC 2012
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?
> 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
> 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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