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trobbins · 14th Oct 2021, 12:25 am

Good to see this has worked out so well. I am preparing a GPSDO based on a eevblog thread that uses the ublox 1Hz output (so no need for a control setting change) and is set up for disciplining a 10MHz OCXO like your setup (a PIC is used to derive the OCXO control rather than your phase comparator). At that frequency I've found that the type of cmos inverter has to be fast with a high current sink/source capability (ie. 74AC04) otherwise the 50 ohm output capability naturally turns to a sinewave even with 4-5 paralleled inverters.

From what I can tell, the cheap ebay NEO-7M GPS module I have aligns very closely with your development board, and also has a micro-USB port so can be tested standalone using u-centre2 software from ublox.

14th Oct 2021, 12:25 am	#13
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	Re: Finally a GPSDO that works Good to see this has worked out so well. I am preparing a GPSDO based on a eevblog thread that uses the ublox 1Hz output (so no need for a control setting change) and is set up for disciplining a 10MHz OCXO like your setup (a PIC is used to derive the OCXO control rather than your phase comparator). At that frequency I've found that the type of cmos inverter has to be fast with a high current sink/source capability (ie. 74AC04) otherwise the 50 ohm output capability naturally turns to a sinewave even with 4-5 paralleled inverters. From what I can tell, the cheap ebay NEO-7M GPS module I have aligns very closely with your development board, and also has a micro-USB port so can be tested standalone using u-centre2 software from ublox.