Hi, Jason, I have a great deal of curiosity about IEEE-1588, but I've always wondered about the precision/stability that's attainable. Compared with multiple sample clocks, correlating signals sampled with one common clock seems far more forgiving vis a vis clock frequency/phase stability. If you or John could point me to any information about this, please do!
Thanks, Dave On May 4, 2015, at 11:44 PM, Jason Manley wrote: > On the far end of the concept spectrum, have you considered distributing time > over your existing ethernet network with IEEE-1588, and using this to > discipline local ovenised 10MHz oscs at each antenna? > > I'm cc'ing Johan Burger, who heads up our Timing and Frequency Reference > subsystem, who might be able to offer some additional insight. I know they've > tried a few different lasers and detectors, with varying levels of success. > > Jason Manley > CBF Manager > SKA-SA > > Cell: +27 82 662 7726 > Work: +27 21 506 7300 > > On 05 May 2015, at 5:18, Bob Stricklin <[email protected]> wrote: > >> Hi Jack and John, >> >> I wanted to add an input here….. >> >> I am working on a 10 MHz GPS slaved reference for my personal use. I am >> working with a Analog Devices AD9548 Evaluation board (~$250) , GPS with 1 >> PPS, and a ovenized 10 MHz osc. I also plan to distribute this clock and >> have considered the Avago fiber product line. One of the older generation >> Avago fiber parts should work fine for <$25 per channel. With careful >> control of lengths and delays it should be possible to maintain good phasing >> between channels. The analog devices chip is <$50 so a custom solution >> should be <$500/reference but with considerable development time. >> >> Bob Stricklin >> >> >>> On May 4, 2015, at 10:02 PM, Jack Hickish <[email protected]> wrote: >>> >>> Hi John, >>> >>> Thanks for the info. I'll add Litelink to my list of suppliers to >>> investigate. >>> We have no particular urge to multiplex the signals on to the fiber unless >>> there's a particularly neat/cheap solution to do that. There's no great >>> appetite to go custom. We've got about ~30 nodes, and my first stab at >>> getting an off-the-shelf solution turned up at a few k$ / node, not >>> including any cleanup electronics. >>> >>> Thanks again, >>> >>> Jack >>> >>> On Mon, 4 May 2015 at 19:25 John Ford <[email protected]> wrote: >>>> Hi CASPERites, >>>> >>>> For HERA, we're looking at distributing timing signals (PPS & 10Mhz ref or >>>> 500 MHz clock) over O(100m) fibers to various digitization nodes. >>>> I figure some folks in CASPERland have experience with this kind of >>>> system? >>>> Did you use custom RF-over-fiber kit, or off-the-shelf PPS/10MHz >>>> solutions? >>>> Any words of wisdom/caution to share? >>>> >>>> Any responses much appreciated! >>> >>> We have several different schemes for the different signals. Are you >>> planning for one fiber per signal per node? or one fiber with the signals >>> multiplexed on them? >>> >>> If the signals are one per signal, you can use some off-the-shelf >>> solutions, but they are kind of pricey, and if you have a lot of nodes to >>> supply, it might be worth working on something custom. We have used Math >>> Associates stuff for this kind of work. Math Associates is now litelink, >>> and they tout the affordability of their stuff, so maybe it's >>> reasonable... >>> >>> >>> On the 10 MHz, we send the 10 MHz reference over fiber, and at the far end >>> use a crystal oscillator locked to the reference to clean up the noise >>> from the fiber electronics. This is essential for interferometry, but >>> maybe not for single-dish use. >>> >>> John >>> >>>> >>>> Jack >>>> >>> >>> >> > >
