Jim Your hitting the nail on the head with my questions. Though I have quite a few GPSDOs, Berts results have my attention. I can also tell that the solution you have should also be relatively low power consumption. Lets see what his 24 hour test does. That said changing to the DAC was a good idea, but that also changed the software. I agree on the SOT 23 technology. I have a microscope and can handle it just barely. There are smaller technologies like msop8s and hand soldering just doesn't work. BGA's heck noooo.
Figuring out the offsets for a ocxo tends to be a challenge. Careful measurements and behavior characterization since everything I ever pickup is random flea market stuff. Regards Paul. On Fri, Apr 5, 2019 at 4:00 PM Jim Harman <[email protected]> wrote: > Paul, > > Yes, I switched from Lars's PWM based DAC to the MCP4725, which is > available on an inexpensive breakout board. I wanted to avoid the original > design's sensitivity to the 5V supply voltage. My OCXO has a 4V reference > output and I use that to power the DAC. I use a resistor network between > the DAC and the VFC pin of the OCXO to shift the DC level and reduce the > control range, effectively increasing the 12 bit resolution of the DAC. A > change I am contemplating is to switch to an AD5680 18 bit DAC which looks > ideal for this application, but I have been put off by the tiny SOT23 > package. > > A schematic is attached. Recent changes, not reflected in this schematic, > are a circuit to linearize the diode-R-C integrator and also output buffers > for the 10 MHz and 1 pps. > > > On Fri, Apr 5, 2019 at 12:10 PM paul swed <[email protected]> wrote: > > > Jim > > The whole gpsdo seems impressive and also seems to be performing well. > > When I look at the Lars GPSDO what you have built doesn't quite seem to > > match. Such as using a real DAC. Is this one of the variants that can > > exist? > > Regards > > Paul > > WB8TSL > > > > > > > > -- > > --Jim Harman > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
