I put a spreadsheet in the Files section on the group page with a simple calculation to zero in on the frequency to enter into the U2 to keep the clock on time for those of us working WSPR without GPS or external PPS reference. (GPS does not work everywhere my WSPR radio goes...)
After several iterations using this calculator, the clock runs quite closely to the time standard. Having the U2 run longer times between calculations will give the best resolution. Try at least 12 hours or more between calculations unless yours is off by several seconds on shorter runs.
The initial value for the reference is the 20 MHz clock crystal. On subsequent runs, use the new value (the one you put into the system clock value field) at the reference so that you can zero in on the actual crystal frequency.
Use a good time standard (WWV or WWVB here in the US) or software which updates your computer clock which is done shortly before finding the offset. For my laptop I use BktTimeSync from mostly because I can use it with a GPS to set the laptop clock in the field when away from an internet connection.
Paul KE7HR in Phoenix, AZ USA
