[time-nuts] GPS W/10KHz

EWKehren at aol.com EWKehren at aol.com
Sat Feb 8 17:50:15 EST 2014


The problem with the PLL analog version is the same as with any digital  
GPSDO. The saw tooth is present at 10 KHz just like 1 Hz. To the best of my  
knowledge there is no GPS receivers out there for less than $ 1000 with out 
saw  tooth. Timing receivers output the correction value and you can either 
with  software or a variable delay do correction.
I encourage you to pursue your idea since for more than ten years I had the 
 privilege to communicate with some of the sharpest minds on that subject 
and  obviously the missed something. 
That also applies for the three of us that have been working intensely on  
developing and testing the next generation of GPSDO's that we hope to 
introduce  to time nuts soon.
In the meantime with the ever increasing price of Tbolts,  Shera is  worth 
a second look. When we worked on the last code release of Shrea using a  
Morion we got consistently better than 1 E-11. Yes some of the IC's are hard to 
 find and that is why I used more readily available parts and did a new 
board  layout. 
Also did one using a $ 1.20 Altera gate array.
Bert Kehren
 
 
In a message dated 2/8/2014 12:33:48 P.M. Eastern Standard Time,  
albertson.chris at gmail.com writes:

On Sat,  Feb 8, 2014 at 3:44 AM, Volker Esper <ailer2 at t-online.de>  wrote:

>
> you don't need 10kHz to build a GPS disciplined  oscillator. GPSDOs are
> build with control loop response times in the  range of some hours, so
> the loop will be absolutely happy with a 1PPS  input.
>


Of course you are correct.  Most GPSDOs are  driven with a 1Hz pulse.  But I
think maybe the OP is not building  just any GPSDO but maybe he is looking
to repair a specific GPSDO that is  designed to use the old (and now rare)
Rockwell GPS.      If  that is the case he needs the old Rockwell or needs
to redesign his  system.

If you are starting from scratch to build a new GPSDO it's  easier now.  All
you need is some kind of a phase detector (74HC4046  ?) and a small uP that
has a good built-in DAC.  The uP checks the  phase once per second and
adjusts it'sDAC accordingly.
-- 

Chris  Albertson
Redondo Beach,  California
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