[time-nuts] GPSDO for my rubber duckie
cook michael
michael.cook at sfr.fr
Tue Aug 2 10:03:21 UTC 2011
Le 02/08/2011 04:35, Michael Sokolov a écrit :
<snip>
> Henry Hallam<henry at pericynthion.org> wrote:
>
>> The parameters you'll want for conversion between MCAT and mean solar
>> time are given daily in the IERS bulletins:
>> http://hpiers.obspm.fr/eop-pc/products/bulletins/bulletins.html
> Yes, I know.
>
>> By making use of these you should be able to do much better than the
>> slightly inelegant leap second rubberization-over-10-seconds method
>> you had proposed. Your rubber seconds should be smooth and
>> continuous, to the limit of the IERS measurement accuracy.
> But that would be quite a bit harder. :-) I'll leave that as an exercise
> for Version 2.0; but I'll start with building 1.0 that does my simple
> rubberization.
I am also looking to create a duck, quacking to MST. I have a T'bolt
for a tick which configures easily for GPS time rather than UTC, though
other GPS receivers could do as well as I wasn't thinking of using the
10MHz source. There are also receivers which provide GPS/UTC locked
10KHz signals as well as 1PPS, ex.Jupiter T that could be another option
for you. . My original idea was to use the IERS data to steer the system
clock frequency to tick to MST. However, I did not want to have to
script a weekly data transfer from the IERS bullitins to get dUT1, and
was hoping that I could get it from the GPS data. Unfortunately, it
seems not to be avialable there, or at least I can't find it. Various
radio time transmissions do carry it, ex. MSF in my neck of the woods,
and as I have lashed up an MSF receiver I may start testing with that,
or more likely a hybrid, just using the dUT1 data from MSF, as MSF
spews legal time rather than TAI. However, even that would only be good
if leap secs do not disappear as the current data format only allows
for a dUT1 of < +/-1 sec with a resolution of 0,1 sec. As an aside,
there does not appear to be anything in the American proposal to abandon
leap seconds to get a larger dUT1 corrections into the radio transmissions.
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