[time-nuts] Ublox GPS

Attila Kinali attila at kinali.ch
Mon Mar 21 18:31:54 EDT 2016


On Mon, 21 Mar 2016 11:23:52 -0400
Bert Kehren via time-nuts <time-nuts at febo.com> wrote:

> Attached is a picture of the Ublox GPS with 1 pps correction. It is clear  
> that its on board limitation is the Maxim DS 1124. An alternative would be 
> two  Micron SY89279UMG's. 
> It brings up the question I had raised before control of the TCXO. Using  
> the house reference, a $ 4  ICS 570 and a $ 12 AD9851 board and a PIC  
> controller using the  the message out of the ublox would result in higher  
> resolution and overcoming the issues with the above devices. It will not solve  the 
> problems widely discussed recently external to our GPS units but eliminates 
>  one set of variables. Also worth exploring is TCXO replacement or 
> injection  locking. 

There is an another way: If you go for the LEA-6T, you have the
TIMEPULSE2 output. If you set it to a value that divides 24MHz, and
set it to the right mode, then you get a relatively stable ouptut
which will change its phase on each fix it gets. With that you can
use a phase detector instead of a TDC on the pulse and thus get
a higher resolution with less non-standard components.

(this is kind of a modification of the James Miller GPSDO with the
Jupiter module)

			Attila Kinali


-- 
Reading can seriously damage your ignorance.
		-- unknown


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