[time-nuts] Re: GPSDO/GNSSDO project: STM32G4 + u-blox ZED-F9T + TDC7200

[dk4ww at gmx.net]

Hi Folks,

SBAS is disabled by default for timing applications using F9T.

RTK corrections works only from F9T to F9T.
you need RTCM 7 ( MSM 7) messages. (RTCM 1077 and more)

SAPOS - the German satellite positioning service
sends RTCM 4 (MSM 4) messages. Works fine with F9P  not for F9T.
You will need one F9T Base sending RTCM 7 massages. The Base works as NTRIP caster .
The NTRIP client F9T reseive RTCM 7 data for finding position. The Time Mode of F9T works only if the client not moving.

cheers

Uwe 

Gesendet mit der mobilen Mail App

Am 07.08.22 um 01:02 schrieb John Ackermann N8UR via time-nuts

> I hesitate to post this because I haven't had time to go back and 
> refresh thoroughly, but I'm not sure how you would apply RTK corrections 
> to the F9T.
> 
> I believe that the "T" models can output RTCM data so can serve as an 
> RTK base station, but only the "P" models have the built-engine to 
> receive corrections via UART or USB and do RTK internally.  So without 
> that, I don't see how you can get corrected time directly from the module.
> 
> (I'm assuming that SBAS doesn't count as "RTK" for this purpose.  I've 
> never experimented with what that would do to the timing output.)
> 
> John
> ----
> On 8/6/22 03:41, Carsten Andrich via time-nuts wrote:
> > On 06.08.22 00:50, Hal Murray wrote:
> >> All of the timing receivers that I'm familiar with assume a fixed 
> >> location.
> >>
> >> Are you sure the F9T will work while moving?
> >> If so, does it maintain the same accuracy?
> > 
> > The F9T datasheet [1] specifies the "operational limits" as ≤ 4 g 
> > dynamics, 80 km altitude, and 500 m/s velocity. The time pulse accuracy 
> > (5 ns absolute, 2.5 ns differential) is specified only for "fixed 
> > position mode", so it may degrade when used on the move.
> > 
> > The F9P RTK positioning accuracy does not degrade substantially for 
> > non-stationary use, as far as I can tell without a 20k€ INS groundtruth. 
> > I hope the same applies to the F9T's timing performance. Verifying that 
> > is one of the reasons behind building the prototype.
> > 
> > [1] 
> > https://content.u-blox.com/sites/default/files/ZED-F9T-00B_DataSheet_UBX-18053713.pdf#page=4 
> > 
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