You can measure the cycle to cycle jitter of the GPS PPS output using the Racal Dana 1992 down to the nanosecond pretty easily with the caveat that it will only measure alternate cycles.
Period mode or Time Interval A to B mode will work for this measurement of a 1 Hz source. If you have a faster source like a 5 Hz output, then you have to use Time Interval A to B mode because Period mode will average multiple pulses over the 1 second gate time. Doing this I can easily see the 60ns granularity of my Garmin GPS18-5Hz. On Mon, 26 Nov 2012 22:29:39 +0100, Fabio Eboli <[email protected]> wrote: >Hello Jacques, and the List. > >Thank you for sharing these docs. >Indeed the PPS specs of the MT3339 are confusing. >Maybe measurement on a living specimen can help? > >I have a R-D 1992 counter, and a GPIB interface. >When I will have the GPS I will be able to log >some data on the PC, although I never tried to use >the Racal Counter remotely I will try. >Also I hope somebody can suggest the best way to test >the PPS from the gps using the Racal 1992, I'm not a >time nut, so I could make gross errors. >I was thinking simply to measure and log the PPS >connected to input A with the counter set to >"Period A", and 10s integration time to gain >more resolution, all this for some (many?) hours. > >Fabio. > >Jacques Tiete <[email protected]> ha scritto: > >> Hello TNutters, >> >> maybe new thread? >> >> you can have a look at two specsheets of the MT3339 chipset on my FTP-site >> 1) http://nixie.ramdac.be/TNutstuff/MT_IT530_Data_Sheet_rev_1_0.pdf >> on page 8 "PPS output 100 ms high pulse, rising edge +/-1 ?s @ >> full second GPS epoch..." so it states +/-1 ?s >> 2) http://nixie.ramdac.be/TNutstuff/gtop module application note >> -a00 _mt3339 series_.pdf >> on page 32 "The accuracy level of 1PPS for GlobalTop GPS module >> is >> within 100ns (same for majority of MTK GPS modules). >> The reference design below can help >> improving this accuracy to >> within 80ns." >> but on page 14 "1PPS signal is an output pulse signal used for >> timing application, its electronic characteristic are listed below: >> 1PPS signal and its pulse width >> with 100ms duration >> Low Voltage level: 0~0.4V >> High Voltage level: 2.8~3.1V >> Duration: 100ms (Firmware >> customization for duration is available) >> Period: 1s Accuracy >> (jitter):10ns" >> >> So what shall we believe? >> The rest of the PDF's make a good read. >> >> 73's >> >> Jacques >> >> >> >> >> Message: 4 >> Date: Fri, 23 Nov 2012 16:44:27 +0100 >> From: Jacques Tiete <[email protected]> >> To: "[email protected]" <[email protected]> >> Subject: Re: [time-nuts] time-nuts Digest, Vol 100, Issue 95 >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset=us-ascii >> >> About: >> { >> Date: Thu, 22 Nov 2012 22:26:24 +0100 >> From: Fabio Eboli <[email protected]> >> To: [email protected] >> Subject: [time-nuts] MT3339 chipset in Globaltop's FGPMMOPA6H >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes"; >> format="flowed" >> >> Hello, while asking info about the FE5682, >> I realized that for another project >> (model plane data logging) I will buy >> some cheap gps modules built around an >> MT3339 chipset. >> In my mind somewhere I stored the fact >> that in the datasheet of these module >> is mentioned the pps output, so I checked >> and the manufacturer is claiming that it >> has "High accuracy 1-PPS timing support >> for Timing Applications (10ns jitter)" >> >> This is the module I'm talking about: >> http://www.mirifica.it/store/gps/342-globaltop-fgpmmopa6h-pa6h.html >> http://www.alcom.be/binarydata.aspx?type=doc/GTop-FGPMMOPA6H-Datasheet-V0A.pdf >> >> Has anybody used this chipset or similar for GPSDO? >> I have no experience with discipled oscillators >> but if there is any hope that the pps out >> of these modules is good for the task maybe >> it's time for me to start reading more about >> the subject. >> The final goal will be to check the timing >> of the Rb I have around. >> >> Thanks, >> Fabio. >> } >> >> Hello TNutters, >> >> I did some test with this module from Adafruit >> (http://www.adafruit.com/products/746) and it seems not a bad unit. >> Tested it together >> with my TBolt and the PPS seems quite stable most of the time, I did >> not do any logging and math on the result, >> just letting the TBolt trigger the scope and apart from the cable >> offset I guess 80% of the time the module was >> within 10 to 15 ns. >> However the specs are not very clear and it is a typical chip for >> mobile use in eg. carnav stuff. I also saw some >> other specs where the jitter was specified as 100ns. and even one >> with a 1 microsec. so I'm a little confused. >> As soon as I have some time I plan to connect this module to a >> BeagleBone and do some testing for an NTP server >> I think the Beagle is better for this than the RaspBerry because of >> the "real" ethernet port. >> >> Greetz, >> >> Jacques Tiete >> 0499 99 83 78 >> [email protected] >> >> Op 23-nov.-2012 om 00:19 heeft [email protected] het >> volgende geschreven >> >> > > > >---------------------------------------------------------------- >This message was sent using IMP, the Internet Messaging Program. > > > >_______________________________________________ >time-nuts mailing list -- [email protected] >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
