Hi TAPPR needs that order for 25 TICC’s …… :)
There are indeed many ways to do it and each has it’s advantages and disadvantages. With a DMTD sort of system, you can’t grab “off the shelf” hardware to get things up and running quickly. Also the isolation / ground loop / spur problem is very likely to get you on a DMTD like system with 20 to 30 devices on the same “party line”. No ideal answer, just a lot of tradeoff’s. Bob > On Mar 17, 2019, at 4:48 PM, Attila Kinali <att...@kinali.ch> wrote: > > On Sun, 17 Mar 2019 10:58:49 -0400 > Bob kb8tq <kb...@n1k.org> wrote: > >> The first thing you need (after all the standards) is a way to do precision >> comparisons of all your devices. There are an infinite number of ways to do >> this. Let’s say you buy 26 TICC’s to do the job ( TAPPR needs 25 ordered to >> get the next batch going so that would solve two problems at once :) ). A >> PPS from a single source with good short term stability (maybe an OCXO) goes >> into one side of all of them. A pps from a DUT goes in the other side (yes >> there are other ways …TAPPR needs that order ….). >> You then have 26 devices each reporting how a single standard compares to >> the “main OCXO”. > > > I would use here a variant of DMTD: Instead of comparing pairs > of standards, have one offset frequency generator feed multiple > mixers, one for each standard. This way, the standards can be > compared to eachother more easily. Downside of this is, that > the precision of this comparison depends on the stability of > the distribution of the offset frequency signal. Though, under > the assumption that ground loops can be kept in check, this > should be easier to ensure than having pair wise comparisons > not drifting away too much. When using TICCs, with their high > measurement rate, I would also go for an offset frequency in > the order of 1kHz instead of the customary 1-10Hz. This will > help getting away from the flicker noise region and also give > a much higher slope of the signal to work with, reducing the > white noise of the measurement. Additonally, this should > also give higher precision at tau = 1s, as the system is now > averaging down from 1ms instead of 100ms (when using 10Hz), > which could potentially give a boost of a factor of sqrt(100ms/1ms) = 10. > > Attila Kinali > > -- > <JaberWorky> The bad part of Zurich is where the degenerates > throw DARK chocolate at you. > > _______________________________________________ > 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.
