[time-nuts] GPS lock of the FE5680. Current experiment and question

[Azelio Boriani]

This is the simplest part if a microprocessor can be used: by the serial
port you get the sawtooth correction in nS to be applied to the sampled
data. The sampled data must be converted to nS or the sawtooth correction
must  be converted in a suitable sampled data correction. It is possible
even to hardware correct the PPS with a delay line before using it  (see
the already mentioned gpstime.com/files/tow-time2011.pdf by Tom Clarck and
Rick Hambly).

On Sat, Feb 11, 2012 at 1:45 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> Another way to build an analog phase detector...
>
> Next layer on the onion is how to get the sawtooth correction out of the
> GPS and into your loop.
>
> Bob
>
>
>
> On Feb 11, 2012, at 12:05 AM, Chris Albertson <albertson.chris at gmail.com>
> wrote:
>
> > All these different suggestions build down to one thing, the precision
> > with which you measure the phase when you sample it each second.  The
> > single flip flop will tell you which half cycle. a simple two bit
> > counter made with two '74 FFs tells you which half cycle and with
> > direction.
> >
> > The "best" maybe  is if you let the PPS set a FF and the 10MHz reset
> > it.  The FF's output gates a constant current to a capacitor and
> > charges it to some voltage.  Then you measure that with a 10-bit ADC.
> >  This measures the phase to maybe 1%, gives you direction and is
> > pretty cheap to build
> >
> > Let's see if I have the numbers right?  If you check a 10MHz signal
> > once per second with just the FF then you have 1E-7.  You would need
> > 1000 seconds for 1E-10.   But if you measure phase to 1/10th of a
> > cycle you get to 1E-10   ten faster.  Right?
> >
> >
> > Chris Albertson
> > Redondo Beach, California
> >
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