[time-nuts] Re: Reducing time-interval noise with RNCAN PPP?

[Bob kb8tq]

Hi

There are a couple of chips out there that work with an 
external 10 MHz standard. The Septentrio Mosaic is one,
there are others. Trimble and others make full up instruments
that will accept a 10 MHz reference. 

Just about any chip set is going to have an oscillator associated
with it. It’s up to the designer of the board to supply “something” 
for that function on the board. There are phase noise constraints 
for that signal (along with likely an odd frequency). 

It is rare to find a chipset that directly “corrects” the oscillator. You
are much better off doing that function externally (if you are after
“Time Nut” grade performance ). 

Bob

> On Oct 17, 2022, at 7:00 AM, Bill Notfaded via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> I'd be interested about GNSS chips that allow external holdover standard?
> Like John suggests is this even a thing?
> 
> Bill E.
> 
> On Sun, Oct 16, 2022, 11:29 AM John Ackermann N8UR via time-nuts <
> time-nuts at lists.febo.com> wrote:
> 
>> That's an interesting question, and I'm interested in what other might
>> have to say.
>> 
>> The first question is, are you thinking of using RTK for real-time
>> correction, or post-processing for after-the-fact?
>> 
>> If real-time, you might want to look at Ole Petter Ronningen's work
>> about using PPP RTK (not necessarily NRCan) to make an extremely good
>> GPSDO -- check out https://www.efos3.com/GPSDO/GPSDO.html (and he has
>> some other very informative pages as well.  That project isn't quite
>> what you're asking about, but it's close enough to give you some
>> starting points.
>> 
>> If post-processing, you can extract clock offset data from the NRCan
>> results that will let you see your local clock performance compared to
>> the GPS constellation with time lags from a few hours for the
>> ultra-rapid corrections to about 17 days for the final corrections.  I
>> think the shortest measurement interval that NRCan PPP supports is 30
>> seconds.  From what I can determine, the noise floor of the measurements
>> is in the mid e-13s at 30 seconds, improving with longer intervals at a
>> -1 slope.
>> 
>> If you're brave enough to unsolder the top of the ZED-F9T module, you'll
>> find a 64-ish MHz TCXO.  Replacing that with a signal synthesized from a
>> better standard might (and I stress "might") provide better short term
>> performance.  It's not an experiment I've tried!
>> 
>> John
>> ----
>> 
>> 
>> On 10/16/22 02:55, Marek Doršic via time-nuts wrote:
>>> Hi,
>>> 
>>> I am measuring time-interval between Ublox RCB-F9T PPS ouput and another
>> clock (e.g. Cs clock), where Ublox is set to time mode with fixed surveyed
>> antenna position and data from time-interval counter are corrected for
>> quatization error using ublox TIM-TP receiver message.
>>> 
>>> How can results from RNCAN PPP procesing be used to further reduce noise
>> in the time-interval data?
>>> 
>>>    .md
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