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 <[email protected]> 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 <[email protected] > > 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 <[email protected]> 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 < >> [email protected]> >> > 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 >> > > >> > > _______________________________________________ >> > > time-nuts mailing list -- [email protected] >> > > To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > > and follow the instructions there. >> > >> > _______________________________________________ >> > time-nuts mailing list -- [email protected] >> > To unsubscribe, go to >> > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> > and follow the instructions there. >> > >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
