Re: [time-nuts] Motorola Oncore M12+T Sawtooth
Hello Tom, On Thu, Jan 29, 2015 at 5:27 PM, Tom Van Baak wrote: > google for: m12 gps sawtooth > I have seen your saw-tooth graphs on leapsecond. It did slightly increase my confidence that all units probably are within this range. I guess I can assume this is the same among all M12 units. > > The +/- 127 comes from the range of 8 bits. > Yes. I just meant to say that the datasheet doesn't state anything about the actual range of the saw-tooth correction message . > > /tvb (i5s) > Thanks. Regards, Tom > > > On Jan 29, 2015, at 12:44 PM, Tom Wimmenhove > wrote: > > > > I've built a bunch of carrier board for the M12+T timing receiver. One > > thing I could not find much information about is the maximum sawtooth > > (which, I assume, related directly to the frequency of the receiver's > > internal LO). I know my particular module outputs a correction values > > between -15 and +15, in which case I could use a DS1023-25 delay-line > chip > > which uses .25ns increments instead of the DS1023-100, which uses 1ns. > This > > would give the overall circuit slightly better linearity. Problem is that > > the datasheet doesn't say anything about this, it just says -128..+127ns. > > Does anyone know if there are receiver units out there that have > different > > LOs ? > > > > Regards, > > Tom > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Motorola Oncore M12+T Sawtooth
The source of the sawtooth is not the GPS receiver L.O., it is the frequency of the master clock in the CPU. The 1PPS line is a GPIO line from the CPU. This means that the 1PPS line is constrained to only change state on the edge of a CPU clock. The CPU can calculate exactly when the the 1PPS line is supposed to change, but if it is a 20 MHz CPU clock, it can only change every 50 ns. The sawtooth correction is the difference between the constrained transition and the ideal transition. --- Graham / KE9H == On Thu, Jan 29, 2015 at 4:27 PM, Tom Van Baak wrote: > google for: m12 gps sawtooth > > The +/- 127 comes from the range of 8 bits. > > /tvb (i5s) > > > On Jan 29, 2015, at 12:44 PM, Tom Wimmenhove > wrote: > > > > I've built a bunch of carrier board for the M12+T timing receiver. One > > thing I could not find much information about is the maximum sawtooth > > (which, I assume, related directly to the frequency of the receiver's > > internal LO). I know my particular module outputs a correction values > > between -15 and +15, in which case I could use a DS1023-25 delay-line > chip > > which uses .25ns increments instead of the DS1023-100, which uses 1ns. > This > > would give the overall circuit slightly better linearity. Problem is that > > the datasheet doesn't say anything about this, it just says -128..+127ns. > > Does anyone know if there are receiver units out there that have > different > > LOs ? > > > > Regards, > > Tom > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Motorola Oncore M12+T Sawtooth
google for: m12 gps sawtooth The +/- 127 comes from the range of 8 bits. /tvb (i5s) > On Jan 29, 2015, at 12:44 PM, Tom Wimmenhove wrote: > > I've built a bunch of carrier board for the M12+T timing receiver. One > thing I could not find much information about is the maximum sawtooth > (which, I assume, related directly to the frequency of the receiver's > internal LO). I know my particular module outputs a correction values > between -15 and +15, in which case I could use a DS1023-25 delay-line chip > which uses .25ns increments instead of the DS1023-100, which uses 1ns. This > would give the overall circuit slightly better linearity. Problem is that > the datasheet doesn't say anything about this, it just says -128..+127ns. > Does anyone know if there are receiver units out there that have different > LOs ? > > Regards, > Tom > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Motorola Oncore M12+T Sawtooth
I've built a bunch of carrier board for the M12+T timing receiver. One thing I could not find much information about is the maximum sawtooth (which, I assume, related directly to the frequency of the receiver's internal LO). I know my particular module outputs a correction values between -15 and +15, in which case I could use a DS1023-25 delay-line chip which uses .25ns increments instead of the DS1023-100, which uses 1ns. This would give the overall circuit slightly better linearity. Problem is that the datasheet doesn't say anything about this, it just says -128..+127ns. Does anyone know if there are receiver units out there that have different LOs ? Regards, Tom ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.