[time-nuts] Strange GPS behaviour

Bob Camp lists at rtty.us
Sun Dec 30 14:18:11 UTC 2012


Hi

When asked about the difference, that's not what the people who wrote the code had to say about it….

Bob

On Dec 30, 2012, at 7:56 AM, Azelio Boriani <azelio.boriani at screen.it> wrote:

> and maybe that reflashing a 1uS nav receiver to have a 100nS timing
> receiver is related only to firmware improvements. Accurate timing is
> mandatory for accurate position/navigation. The CW12 timing receiver has a
> position hold mode that can't be turned off but always gives the computed
> position.
> 
> On Sun, Dec 30, 2012 at 12:50 PM, Magnus Danielson <
> magnus at rubidium.dyndns.org> wrote:
> 
>> On 30/12/12 10:06, bg at lysator.liu.se wrote:
>> 
>>> Hi Magnus,
>>> 
>>> 2) Timing versions might get an upgraded oscillator. Maybe a TCXO
>>>>> instead
>>>>> of a standard XO.
>>>>> 
>>>> 
>>>> Don't think so. The noise and systematic stability is as important for
>>>> positional as for timing versions, the timing version can benefit of the
>>>> fixed position.
>>>> 
>>> 
>>> Look at the uBlox6 lineup. Position receivers are available with XO or
>>> TCXO - timing only with TCXO.
>>> 
>>> http://www.u-blox.com/images/stories/linecards_u-blox_gps_modules_2012.pdf
>>> 
>> 
>> In that case they are the first to do it to my knowledge.
>> 
>> None of the Motorola receivers did it as I recall it. Could be that the
>> price of the modules is now so low that the difference make sense.
>> 
>> Notice that producing higher navigational rate is easy if you have the CPU
>> power to do it, and todays receivers have higher CPU power than they used
>> to, so doing 10 Hz navigation rate isn't unfeasable, so it does not need to
>> be Kalman filter predictor results.
>> 
>> Cheers,
>> Magnus
>> 
>> 
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