On 6/16/17 10:55 PM, Lifespeed via time-nuts wrote: > Not too surprising to read locking two crystal oscillators together > without using a physical cable is difficult to impossible. > Essentially what I am looking for is the phase alignment accuracy > (and phase noise) one would get PLL’ing one oscillator to the other > using a cable, but over a longer distance. Some modest phase noise > degradation might be acceptable, but not an order of magnitude. > Clearly not a trivial problem. Yes, the jitter (phase noise) > typically accomplished from a PLL phase comparing at 100MHz is better > than what one could get “locking” to GPS. It was just a thought, > apparently not a realistic one. Thanks for disabusing me of that > notion. > Well, at JPL we regularly lock two crystal oscillators together that are over a billion km apart with added Allan deviation of less than 1E-15 at 1000 seconds with a radio link at 7.15 GHz. It's how we measure the distance and velocity to spacecraft (a few cm in range and mm/s in velocity) and from that figure out the gravitational fields (among other things) So it is *doable* The performance depends ultimately on the noise within your tracking loop bandwidth.

Yes, one has to lock them at a high reference frequency so as to avoid multiplied-up phase noise. I can manage the tracking loop design. Some applications aren't line-of-sight, so the radio link doesn't solve every situation. Fiber optic backup plan, but everybody hates cords. This is my application as well, phase measurement of the signals separated by some distance. Not a billion km, but even a few km requires similar considerations. Lifespeed -----Original Message----- From: jimlux [mailto:jimlux@earthlink.net] Well, at JPL we regularly lock two crystal oscillators together that are over a billion km apart with added Allan deviation of less than 1E-15 at 1000 seconds with a radio link at 7.15 GHz. It's how we measure the distance and velocity to spacecraft (a few cm in range and mm/s in velocity) and from that figure out the gravitational fields (among other things) So it is *doable* The performance depends ultimately on the noise within your tracking loop bandwidth.

sorry about, but who is 'lifespeed', a robot or a real person with a natural name? many thanks, 73, Arnold, DK2WT Am 17.06.2017 um 23:07 schrieb Lifespeed via time-nuts: > Yes, one has to lock them at a high reference frequency so as to avoid multiplied-up phase noise. I can manage the tracking loop design. Some applications aren't line-of-sight, so the radio link doesn't solve every situation. Fiber optic backup plan, but everybody hates cords. > > This is my application as well, phase measurement of the signals separated by some distance. Not a billion km, but even a few km requires similar considerations. > > Lifespeed > > -----Original Message----- > From: jimlux [mailto:jimlux@earthlink.net] > > Well, at JPL we regularly lock two crystal oscillators together that are over a billion km apart with added Allan deviation of less than 1E-15 at > 1000 seconds with a radio link at 7.15 GHz. It's how we measure the distance and velocity to spacecraft (a few cm in range and mm/s in > velocity) and from that figure out the gravitational fields (among other > things) > > So it is *doable* > > The performance depends ultimately on the noise within your tracking loop bandwidth. > > > > _______________________________________________ > 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.

		Attila Kinali

On Sat, 17 Jun 2017 06:29:02 -0700 jimlux <jimlux@earthlink.net> wrote: > Well, at JPL we regularly lock two crystal oscillators together that are > over a billion km apart with added Allan deviation of less than 1E-15 at > 1000 seconds with a radio link at 7.15 GHz. It's how we measure the > distance and velocity to spacecraft (a few cm in range and mm/s in > velocity) and from that figure out the gravitational fields (among other > things) This sounds interesing. What do I have to google for to learn more? Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson

On 6/18/17 7:10 AM, Attila Kinali wrote: > On Sat, 17 Jun 2017 06:29:02 -0700 > jimlux <jimlux@earthlink.net> wrote: > >> Well, at JPL we regularly lock two crystal oscillators together that are >> over a billion km apart with added Allan deviation of less than 1E-15 at >> 1000 seconds with a radio link at 7.15 GHz. It's how we measure the >> distance and velocity to spacecraft (a few cm in range and mm/s in >> velocity) and from that figure out the gravitational fields (among other >> things) > > This sounds interesing. What do I have to google for to learn more? > It's just how we do radio science/ranging - you transmit a spectrally pure signal from earth (typically oscillator locked to a maser), at the spacecraft you have a very narrow band PLL (traditionally a VCXO) that locks to the received signal, and you generate the downlink signal from that same oscillator, transmit it back to earth, and compare. The transmitted signal is precisely in a specified ratio with the received signal (880/749 for X-band 7.15 GHz from earth, 8.4 GHz coming back). For Ka-band, the earth signal goes up at 34 GHz, and comes back at 32 GHz A typical spec is that the transponder introduce no more than 4E-16 ADEV at 1000 sec. https://descanso.jpl.nasa.gov/ has links to a whole bunch of useful references https://descanso.jpl.nasa.gov/monograph/mono.html specifically volume 1 by Thornton and Border talks all about radiometric ranging. The various design and performance series describe the specific implementations. Joe Yuen's "Deep Space Telecommunications Engineering" https://descanso.jpl.nasa.gov/dstse/DSTSE.pdf Chapter 3 covers receiver design Chapter 4 covers radio tracking -- Then you can look for papers on "deep space transponder" The classic design papers are in the 90s. IEEE MTT, and the JPL IPN progress reports. The Cassini Deep Space Transponder is sort of a progenitor of them - then there's the Small Deep Space Transponder (SDST) designed in the 90s, flying 2000 through now. Somewhere around 2000, the design started moving away from trying to lock the oscillator to doing the phase lock and phase/frequency turnaround in a digital loop, with a fixed oscillator driving DDS or NCO. At JPL, this would be the "Advanced Deep Space Transponder", but Thales Alenia Space Italia (TASI) uses a similar approach for their deep space transponders (look for Juno and BepiColombo)

Jim - Your first thread in this post was fascinating to me - stuff I'd never been exposed to. It seems like the 'tricks of the trade' for so much of how things actually get done are so often only accessible to those who work closely with them. I was about to shoot you an email to ask if there was any reference (other than piles of journal articles) that cover some of these topics, when I scrolled down and found this post with the Descanso links and references. What a trove! There's more info in the links on that page than I could ever hope to comprehend. Many thanks for this post. It will remain marked and in the back of my brain as "stuff that you should learn". If we only ever had enough time. Why didn't anyone ever expose me to this stuff when I was young and just starting in RF? Brent On Sun, Jun 18, 2017 at 1:36 PM, jimlux <jimlux@earthlink.net> wrote: > On 6/18/17 7:10 AM, Attila Kinali wrote: > >> On Sat, 17 Jun 2017 06:29:02 -0700 >> jimlux <jimlux@earthlink.net> wrote: >> >> Well, at JPL we regularly lock two crystal oscillators together that are >>> over a billion km apart with added Allan deviation of less than 1E-15 at >>> 1000 seconds with a radio link at 7.15 GHz. It's how we measure the >>> distance and velocity to spacecraft (a few cm in range and mm/s in >>> velocity) and from that figure out the gravitational fields (among other >>> things) >>> >> >> This sounds interesing. What do I have to google for to learn more? >> >> > It's just how we do radio science/ranging - you transmit a spectrally pure > signal from earth (typically oscillator locked to a maser), at the > spacecraft you have a very narrow band PLL (traditionally a VCXO) that > locks to the received signal, and you generate the downlink signal from > that same oscillator, transmit it back to earth, and compare. > > The transmitted signal is precisely in a specified ratio with the received > signal (880/749 for X-band 7.15 GHz from earth, 8.4 GHz coming back). For > Ka-band, the earth signal goes up at 34 GHz, and comes back at 32 GHz > > A typical spec is that the transponder introduce no more than 4E-16 ADEV > at 1000 sec. > > > https://descanso.jpl.nasa.gov/ has links to a whole bunch of useful > references > > https://descanso.jpl.nasa.gov/monograph/mono.html > specifically volume 1 by Thornton and Border talks all about radiometric > ranging. > > The various design and performance series describe the specific > implementations. > > Joe Yuen's "Deep Space Telecommunications Engineering" > https://descanso.jpl.nasa.gov/dstse/DSTSE.pdf > Chapter 3 covers receiver design > Chapter 4 covers radio tracking > > -- > > Then you can look for papers on "deep space transponder" The classic > design papers are in the 90s. IEEE MTT, and the JPL IPN progress reports. > > The Cassini Deep Space Transponder is sort of a progenitor of them - then > there's the Small Deep Space Transponder (SDST) designed in the 90s, flying > 2000 through now. > > Somewhere around 2000, the design started moving away from trying to lock > the oscillator to doing the phase lock and phase/frequency turnaround in a > digital loop, with a fixed oscillator driving DDS or NCO. At JPL, this > would be the "Advanced Deep Space Transponder", but Thales Alenia Space > Italia (TASI) uses a similar approach for their deep space transponders > (look for Juno and BepiColombo) > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. >