Re: [time-nuts] PLL/GPSDO/etc learning resources for mere mortals
On 9/3/18 5:52 AM, Richard (Rick) Karlquist wrote: Also worth checking out "Dean's book": http://www.ti.com/tool/PLL_BOOK This makes a great introductory text/prerequisite for the heavy hitters like Gardner and Rohde. Dean Banerjee spent many years providing customer -- john, KE5FX You hit a home run ... this is a great tutorial. This reminds me of the saying "equations don't teach.". I love the graph on page 1 that has "VCO" and "everything but the VCO" marked. Yet another reason to keep reading time-nuts. Dean's book is great. Can you print from the pdf? Back in version 3 or so, it was one of those "can't print" pdf files (which I'm sure could be broken by a non Adobe reader). So I bought a printed copy - worth every penny of the $15. It's the book I hand out to people when they start asking about how to do a PLL circuit. "Here, this book is sort of like the master application note...Read it and start finding out what went wrong." ___ 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.
Re: [time-nuts] Frequency over fiber (was WWV and legal issues)
FWIW the round-trip delay on our 900km White Rabbit link looks like so (lower graphs. upper are a local Cs-clock vs. the fiber-time): http://monitor.mikes.fi/mikes_kaja/ No fault-lines, earthquakes, or volcanoes in Finland I'm afraid. That's a standard 2-fiber (separate TX and RX fibers) DWDM system with amplifiers, multiplexers, and dispersion-compensation fibers - in addition to the actual fiber-spans. diurnals on the 10.5 ms RTT seem to be around 80ns this time of the year. Larger jumps are fiber/equipment repairs. The recent earthquake paper on the London-Paris link is this one I think: https://arxiv.org/ftp/arxiv/papers/1801/1801.02698.pdf Anders On Sun, Sep 2, 2018 at 11:14 PM Peter Vince wrote: > Hi Magnus, > > Could you please give us some idea of the magnitude of these effects? > Even if just whether we are talking about nano, pico, or femtoseconds? > > Thank you, > > Peter > > > On 2 September 2018 at 12:17, Magnus Danielson > > wrote: > > > Hi Gerhard, > > > > I see that this became a separate thread. > > ... > > ... > > > > Acoustical sensitivity, low frequency changes. > > > > For optical clocks and frequency transfer, just the vibration from > > traffic and other activity causes disturbances which disturbes the group > > delay. What is done for these links is to actively compensate then using > > a return path and closing the loop with a controller, very much like a > > PLL. The length of the loop limits the bandwidth and hence how high up > > the compensation can be done, so for longer stretches, this needs to be > > repeated. They have now built links from PTB to SYRTE and NPL. > > > > Temperature shifts are slower, but also compensated though the active > loop. > > > > Close proximity to strong power-currents have also been shown to cause > > modulations, so separate from power-cables if you can. > > > > Remember that the end nodes have very stable clocks, so their effects > > can be taken out of the equation. For other setups, such as telco > > operation, that's a completely different ballgame. > > > > Cheers, > > Magnus > > > ___ > 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.
Re: [time-nuts] PLL/GPSDO/etc learning resources for mere mortals
li...@packetflux.com said: > I'm trying to fill in some gaps in my knowledge about PLL's, GPSDO's, etc., > with the goal to eventually implement some of these either in a > microcontroller or fpga or some combination thereof. An FPGA is unlikely to be the way to go for a GPSDO. There is lots of time to do it in software and the tools for micros are generally easier to work with than FPGA tools. (But if you like FPGAs, don't let me scare you away.) One thing to keep in mind for GPSDOs is that the time constants for filters are very long relative to what is reasonable to build with Rs and Cs that are readily available. The usual way to go is a D/A connected to a micro. That moves the filter time constant into software. Thus you will see lots of discussion on this list about which D/A to use. Generally, you would like more bits than you can get. For a one-off project, you can trade a reduced tuning range for better resolution if you are willing to use a pot (or soldering iron) for the coarse adjustment, aka the high bits on the tuning range. Another thing to add to your list is hanging bridges and sawtooth correction. Another magic term associated with PLLs is PID controller - Proportional, Integral, Differential. You may find some web articles that tell you enough to be helpful without using complicated math. -- These are my opinions. I hate spam. ___ 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.
