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

[paul swed]

Looks like analog devices makes a pretty nice sample and hold chip. A bit
pricey.
But can't really work at 10 MC so that would complicate things

On Sat, Feb 11, 2012 at 10:54 AM, paul swed <paulswedb at gmail.com> wrote:

> Getting very interesting.
> Bob had mentioned just sample the 10 MC sine wave. What I used to do on
> homebrew Loran C.
>
> Thats easier to do because today its nothing to buffer that 10 MC signal
> to drive a fast sample and hold. This eliminates the ramp circuitry and
> constant current sources used in the ramp and tempco effects.
>
> This all seems to work out reasonably because the 5680s are in general
> pretty darn stable. (Boy is that a relative term in time-nuts land)
>
> Now to dig through the ole junk box for a sample and hold chips. Most
> likely older and useless. Go hunting at mouser or digikey for modern stuff.
> Hate to have to go to discrete pulsed diodes.....
> Regards
> Paul.
>
>
>
> On Sat, Feb 11, 2012 at 10:33 AM, Azelio Boriani <azelio.boriani at screen.it
> > wrote:
>
>> 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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