Hi Actually a minimalist GPSDO *could* be a person looking at a scope and tweaking a pot every so often. It all depends on what the desired result is (how accurate / how automated / how failure resistant). Is simplicity measured by low cost, low parts count, easy to find parts, or easy to work with parts? Do parts I already have (OCXO, Rb, GPS) count or not? Does time matter or just frequency? Is there a "that's good enough" level (as in do you need a GPSDO at all)? Does design time count / does it need to be an existing design?
Without some definition, there really is no way to answer. Bob On Jan 1, 2012, at 6:23 AM, Tom Harris wrote: > I too have been mulling over a minimal GPSDO. > > Has anyone mentioned a PWM DAC? Even a "toy" microcontroller like the > Atmel AVRs can generate 16 bit resolution PWM, which sounds like it > would be heaps. As long as the voltage reference is low noise, it does > not matter if it drifts slowly, since the control loop adjusting the > OCXO frequency will adjust it. Of course you will need a long time > constant filter to smooth the PWM, but a 2 pole filter constructed > from an opamp will do the job. > > The micro can also capture the 1PPS from the GPS if it is clocked by > the OCXO, and use the value to close the control loop. > > So a minimal GPSDO looks like a simple microcontroller (I would use > Arduino since we use these at work whenever we need to build something > in an afternoon) with a filter for a PWM DAC, so one opamp and a few > discretes. Of course as I write software for such beasts as a trade I > am giving the software a zero cost. > > On 31 December 2011 06:46, Stanley <timen...@n4iqt.com> wrote: >> >> >>> >>>> "What is the simplest design for a GPSDO that uses only the PPS signal >>>> from >>>> a modern GPS?" >>> >>> >>> Some sort of oscillator with a voltage control. >>> CPU with a timer/counter that can capture the PPS. >>> DAC. >>> Software. >>> >> >> How about MSC1200 : http://www.ti.com/lit/ds/symlink/msc1200y3.pdf >> >> Stanley >> >> _______________________________________________ >> 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. > > > > -- > > Tom Harris <celephi...@gmail.com> > > _______________________________________________ > 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.