On Tue, Dec 8, 2009 at 3:43 PM, Bruce Griffiths <[email protected]> wrote: > Alexander Sack wrote: >> >> On Tue, Dec 8, 2009 at 3:01 AM, Robert Atkinson<[email protected]> >> wrote: >> >>> >>> Hi Alexander, >>> Welcome to the list. >>> Another professional option is the Trimble Accutime Gold. >>> http://www.trimble.com/timing/ The older Accutime 2000 and Palisade turn up >>> on ebay. A desk top box is the CNS Clock II >>> http://www.cnssys.com/cnsclock/CNSClockII.php cost about $3000 complete. >>> Some idea on if you want new / professional or used / amateur and if you >>> are a keen constructor would allow more targeted advice. >>> >>> >>> >> >> Thanks Robert! >> >> Yeah I didn't really specify price or performance metrics in my >> request. I think I should document this stuff and write up a >> beginner's FAQ (I didn't see anything on LeapSecond.com). >> >> Alright, the reason WHY I didn't actually specify much is because I >> really don't know WHAT to look for. I found out today that the >> rinky-dinky Endrun Technologies Cf/Ct receivers are 1k each (GPS and >> CDMA variants)! I was kinda shocked because there ain't much to these >> units AFAIK. So I want to step back for a second (pun intended?) and >> ask everyone, WHAT SHOULD I BE LOOKING FOR? Say I want nanosecond >> accuracy with respect to the PPS rising edge to absolute UTC....I know >> that for sure. My target system is FreeBSD though I would like to use >> something with Snow Leopard as well (even if that's just ntpd synced >> locally to the FreeBSD box). I am interested in running NanoBSD on a >> stand alone system. >> >> As for as assembly, I'm open, though I haven't soldered anything since >> undergraduate engineering school in a lab. I am a software guy by >> trade. >> >> Another issue is what governs the price of these units? I'd like to >> think its not going to be like the audio industry. >> >> Hope that helps, >> >> -aps >> >> > > Alexander > > If you want the best performance possible from nanobsd then using an M12M or > M12+T is advisable. > In this case hardware timestamping (with a resolution of about 100ns) of the > PPS signal is used together with a customised version of the driver created > by Poul-Henning Kamp. > > The cheapest option would be to obtain used M12+T timing receiver boards. > however using these would entail constructing a board with a TTL/CMOS to > RS232 transceiver and adding a 50 ohm driver for the PPS signal (required > for highest time stamping precision as it avoids the delay of an RS232 > driver and receiver). The only complication being that the receiver board > uses a mating connector with 1.27mm pitch rather than the more common 2.54mm > pitch connectors used by older receivers.
Ahh thanks for this info. I was gravitating toward trying to setup something similar using phk's ntpd driver? I need to read more. > Of course network congestion and queueing delays add to the timing noise > seen by client machines on the network. Right. > If one used PTP (IEEE 1588) instead of ntp then the performance can be > substantially improved if one can avoid standard network switches with their > queueing delays. > However PTP is relatively new and as yet IEEE 1588gear hasn't yet hit the > surplus market. > Usually PTP uses hardware timestamping of the relevant network packets, > however there have been some efforts at software timestamping. Yes but in fact I would like to play with IEEE 1588 as well for work reasons! -aps _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
