I was slightly imprecise in my previous posting about ubx timing modules and a few people have raised queries in the list or by email. What I should have said is that this module is designed as a precise low-noise /frequency /reference so it directly generates the 30.72 MHz needed in LTE infrastructure from a GPS disciplined VCTCXO. As I understand it, the usual 10 MHz output is digitally generated and jitters, so can't be used as a reference in high performance radio systems. One could use a phase-locked synth to multiply up from the 1 PPS signal but given the large ratio needed this is prone to generating its own noise. The M8F does it all internally and is therefore preferred if what you want is a low noise frequency reference, though its frequency may not be ideal if for example you wanted 10 MHz - you could get 10.24 MHz by dividing by 3 but 10 MHz is trickier. -- John Haine 9 Parkway Shudy Camps Cambridge CB21 4RQ 01799 584773 (T) 07841 322831 (M)

I was slightly imprecise in my previous posting about ubx timing modules and a few people have raised queries in the list or by email. What I should have said is that this module is designed as a precise low-noise /frequency /reference so it directly generates the 30.72 MHz needed in LTE infrastructure from a GPS disciplined VCTCXO. As I understand it, the usual 10 MHz output is digitally generated and jitters, so can't be used as a reference in high performance radio systems. One could use a phase-locked synth to multiply up from the 1 PPS signal but given the large ratio needed this is prone to generating its own noise. The M8F does it all internally and is therefore preferred if what you want is a low noise frequency reference, though its frequency may not be ideal if for example you wanted 10 MHz - you could get 10.24 MHz by dividing by 3 but 10 MHz is trickier. John Haine ================================== I discovered an interesting comparison with the Jackson LTE-Lite here: http://www.jackson-labs.com/assets/uploads/main/Comparative_analysis.pdf Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-taylor@blueyonder.co.uk Twitter: @gm8arv

There was an interesting comment in the Lea-m8f datasheet, "In strong signal clear-sky applications the best time pulse consistency between neighbouring receivers is achieved when using a single GNSS because of the small time offsets between different GNSS systems. " On Thu, Dec 22, 2016 at 8:01 AM John Haine <john.haine@haine-online.net> wrote: > I was slightly imprecise in my previous posting about ubx timing modules > > and a few people have raised queries in the list or by email. > > > > What I should have said is that this module is designed as a precise > > low-noise /frequency /reference so it directly generates the 30.72 MHz > > needed in LTE infrastructure from a GPS disciplined VCTCXO. As I > > understand it, the usual 10 MHz output is digitally generated and > > jitters, so can't be used as a reference in high performance radio > > systems. One could use a phase-locked synth to multiply up from the 1 > > PPS signal but given the large ratio needed this is prone to generating > > its own noise. The M8F does it all internally and is therefore > > preferred if what you want is a low noise frequency reference, though > > its frequency may not be ideal if for example you wanted 10 MHz - you > > could get 10.24 MHz by dividing by 3 but 10 MHz is trickier. > > > > -- > > John Haine > > 9 Parkway > > Shudy Camps > > Cambridge > > CB21 4RQ > > > > 01799 584773 (T) > > 07841 322831 (M) > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > >

Hi There are a couple of issues in multi GNSS timing. One is the basic time offset between systems (maybe a few ns, maybe a lot more). The next is the accuracy of the estimate of that offset (again maybe a few ns, maybe …). After that you get into things like survey accuracy. Position hold is a single fixed location that gets applied to all systems. If the “right”survey is here for this system and there for that system, there will be an error one way or the other. Do they agree to CM or M or 10’s of M? Some places they agree very well. Other places not so much …. Lots of messy details. Bob > On Dec 22, 2016, at 12:23 PM, Scott Stobbe <scott.j.stobbe@gmail.com> wrote: > > There was an interesting comment in the Lea-m8f datasheet, > "In strong signal clear-sky applications the best time pulse consistency > between neighbouring receivers is > achieved when using a single GNSS because of the small time offsets between > different GNSS systems. " > > > On Thu, Dec 22, 2016 at 8:01 AM John Haine <john.haine@haine-online.net> > wrote: > >> I was slightly imprecise in my previous posting about ubx timing modules >> >> and a few people have raised queries in the list or by email. >> >> >> >> What I should have said is that this module is designed as a precise >> >> low-noise /frequency /reference so it directly generates the 30.72 MHz >> >> needed in LTE infrastructure from a GPS disciplined VCTCXO. As I >> >> understand it, the usual 10 MHz output is digitally generated and >> >> jitters, so can't be used as a reference in high performance radio >> >> systems. One could use a phase-locked synth to multiply up from the 1 >> >> PPS signal but given the large ratio needed this is prone to generating >> >> its own noise. The M8F does it all internally and is therefore >> >> preferred if what you want is a low noise frequency reference, though >> >> its frequency may not be ideal if for example you wanted 10 MHz - you >> >> could get 10.24 MHz by dividing by 3 but 10 MHz is trickier. >> >> >> >> -- >> >> John Haine >> >> 9 Parkway >> >> Shudy Camps >> >> Cambridge >> >> CB21 4RQ >> >> >> >> 01799 584773 (T) >> >> 07841 322831 (M) >> >> >> >> _______________________________________________ >> >> time-nuts mailing list -- time-nuts@febo.com >> >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> >> and follow the instructions there. >> >> > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.