[time-nuts] 1 pps correction

[EWKehren at aol.com]

Chris
 do you or any one else have a micro controller and code for  such an 8 pin 
solution? The rest I would know how to do.
Bert Kehren
 
 
 
In a message dated 4/7/2012 12:12:40 P.M. Eastern Daylight Time,  
albertson.chris at gmail.com writes:

The  simplest way to do this is to use a "standard" GPS and let if
drive a  GPSDO.  Yes you can try and build a copy of a T-bolt but how
many  engineering ours do you think Trimble spent on that?  Well over a
man  year I'd say and few people have the range of skills needed to do
it all  themselves.

If you want to use the sawtooth data in the GPSDO then  you'd need a
one of those very small 8-pin micro controllers.  It  could "tap" the
serial line and listen for the sawtooth correction and then  output a
voltage on an analog pin.   The sawtooth correction does  not change
very fast so the bandwidth is low enough for something like an  AVR or
PIC.  This uP would have only one function so the software  would be
easy
I think you'd use the analog sawtooth voltage to slightly  bias the
phase detector.



On Sat, Apr 7, 2012 at 3:59 AM,  Attila Kinali <attila at kinali.ch> wrote:
> On Sun, 1 Apr 2012  19:10:59 +0000
> shalimr9 at gmail.com wrote:
>
>> It seems  to me that if standalone GPS timing receivers used a VCXO
>> instead  of a fixed frequency clock, the cost delta would not be that
>>  significant, and they too could avoid the need for sawtooth  correction.
>
> Not really. You'd need a low noise, low DNL, high  resolution DAC to
> stear the VCXO. Analog electronic costs considerably  more than a tiny bit
> of software and eats a lot more  power.
>
> Maybe you can get away with using one of the Silicon  Labs programmable
> oscillators instead of a VCXO and a DAC. But IIRC  they only have a
> frequency setting, no phase setting, so you need some  way to fix the
> phase offset.
>
>        Attila  Kinali
>
>
> --
> Why does it take years to find the  answers to
> the questions one should have asked long  ago?
>
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-- 

Chris Albertson
Redondo  Beach,  California

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