Thanks Forrest, I've added this to my documentation packed for my own PRS-10; I suspect that I'm only a year or two from (possibly) needing it myself.
Dana On Fri, Sep 13, 2019 at 3:00 AM Forrest Christian (List Account) < li...@packetflux.com> wrote: > Mainly wanting to post this to the list so it will end up in the archives. > > So I decided to give calibration/adjustment of my bench PRS-10 a go. > > What I discovered is that on my particular unit, the frequency was enough > off that in order to bring it close to spec, I had to adjust the Mag Offset > to the lower end of it's range (2300), and even then the set frequency was > lower than I would have liked. > > According to the section of the manual under the SP command, if the Mag > Offset is at the end of it's range, you can change the frequency > synthesizer's parameters by querying the existing SP? settings, finding the > row in Appendix A which corresponds to those values, then changing the SP > value up or down a step (by using the values in the table row just above or > below the value). > > In my unit, the SP value set (6114,3436,29) were not anywhere to be found > in Appendix A. > > After some digging, and reading the manual, I discovered that these values > are used to configure the MC145193 inside the PRS-10. Specifically the > first value (R) is used to divide the 10Mhz output. The second two values > (N, A) are used to divide 359.72Mhz (which is related to the Rb > frequency). This second divisor is calculated by (N*64+A). The resulting > two divided down signals will be very close in frequency, and the > difference is used to stabilize the oscillator. > > After some more work, I discovered that the divisor values currently in my > oscillator were actually exactly 3 times the value of row 52, that is > 6114/3=2038 and (3436*64+29)/3=(2038*64+31). Since it's only the ratio > between the divisors which matter, I'm assuming someone at some point > decided to use the higher division ratio for some reason. Not sure if this > was at SRS or in the field. > > After discovering this, I followed the procedure to move the SP values by > one row in the table, and everything seems to have re-centered itself. > > Hope this helps someone... Even if it's me in the future if I have to do > this again. > > -- > - Forrest > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.