Re: [time-nuts] ntp and asymmetric delays
Yes, I think you are correct except in one case. The NMEA offset may very well be mostly because the NMEA sentence is actually "off". Such sentences may be as much as a full second "off". First the NMEA standard requires only one second accuracy and also the sentence is sent over a slow serial link along with other data and when you get it depends a lot on what they "other data" is. This is the reason the GPS has a PPS. NMEA was invented for ship navigation, not timing. On Tue, Oct 11, 2016 at 10:09 AM, Thomas Valerio wrote: > I was going to post my ntp output and ask for an opinion, then this > discussion popped up. It would appear that asymmetric delays are the > exact explanation for what I am seeing. -- Chris Albertson Redondo Beach, California ___ 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.
Re: [time-nuts] HP 59309A Clock runs, sets via GPIB, but no GPIB output?
Interested if no one has already spoken got the HP59309. Jeremy N6WFO On Tuesday, October 11, 2016, Bert Kehren via time-nuts wrote: > Cleaning up I ran across today a HP59309, if some one is interested please > contact me off list before I put it on ebay. > Bert Kehren > > > In a message dated 10/11/2016 1:54:20 P.M. Eastern Daylight Time, > francesco.messi...@gmail.com writes: > > 1818-2295A dump has been uploaded to ko4bb site, probably there's need > to be moved in the right place before it's available. > > On Mon, Oct 10, 2016 at 9:32 AM, Francesco Messineo > > wrote: > > Hi Dave, > > right, once I find the dumps, I'll upload them. > > thanks > > Frank IZ8DWF > > > > On Mon, Oct 10, 2016 at 9:24 AM, Artek Manuals > > wrote: > >> Frank > >> > >> One of the best places to store ROM dumps for easy access by everyon is > >> KO4BB.com > >> > >> Dave > >> NR1DX > >> dit dit > >> > >> On 10/10/2016 3:20 AM, Francesco Messineo wrote: > >>> > >>> I have a dump of the 1818-2295A somewhere, it should be archived in > >>> one of my backups. I also made a replacement with a board having 2 x > >>> 28C64 SO-28 eeproms and it worked in my 59309A as far as I could test > >>> it. However these eeproms present many glitches on the outputs during > >>> address toggling, so it's way better to use a suitable CPLD after > >>> recovering the equations (I'm a bit stuck on this project due to lack > >>> of time...). > >>> If someone needs the dump, just let me know and I'll dig it out. > >>> HTH > >>> Frank IZ8DWF > >> > >> > >> > >> -- > >> Dave > >> manu...@artekmanuals.com > >> www.ArtekManuals.com > >> ___ > >> 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. > ___ > 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. > > ___ > 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. > -- Sent from Gmail Mobile ___ 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.
Re: [time-nuts] ntp and asymmetric delays
There is good article to read http://cs.stackexchange.com/questions/103/clock-synchronization-in-a-network-with-asymmetric-delays Probably NTPD uses a weighting schema when processing the measurements. However, beyond a certain level of delay the measurements are likely to be so corrupted as to be useless. On 2016-10-11 13:09, Thomas Valerio wrote: I was going to post my ntp output and ask for an opinion, then this discussion popped up. It would appear that asymmetric delays are the exact explanation for what I am seeing. Is that a reasonable assumption? It does seem to be rather consistent throughout the day, however. The reason for checking against the net when I have a GPS source is that I want ntp to continue if/when there is no PPS. Is there any way to inform ntp of the asymmetry? Thanks, -- Thomas Valerio Every 20.0s: /usr/sbin/ntpq -n -c pe pe Tue Oct 11 12:37:33 2016 remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l4 16 3770.000 -30.300 36.009 *127.127.28.1.PPS.0 l3 16 3770.0000.001 0.000 -208.53.158.34 216.93.242.123 u9 64 377 17.2022.907 0.188 +208.100.4.52216.86.146.462 u 64 64 377 16.6122.332 0.193 +208.69.120.241 142.66.101.132 u5 64 377 24.2581.688 0.223 -128.118.25.3130.207.244.240 2 u 53 64 377 40.4294.956 2.577 Hi NTP can *not* detect âcommon modeâ asymmetric delay. Having a local GPS does not count in this respect. What does count is an NTP client / server sitting in your home trying to figure out what time it is only by hooking to the internet. To do this it must do a few things: 1) Get a signal out through the (slow / long lag) upload channel on your modem. 2) Route that signal through the cable guyâs low capacity upstream network to one of his (at best) two or three gateways to your local empire. These may or may not be in the same state you live in. 3) Fly the signal over the backbone to whatever server is involved. 4) Fly a signal back over the backbone to possibly another set of gateways. 5) Route that signal through the cable guyâs high capacity downstream network. 6) Run it through the (quite fast / low lag) downstream channel on your modem. Steps 1,2,5 and 6 are common to every single server you try to access. If your modem has an âupstreamâ lag of (say) 101 ms and a âdownstreamâ lag of (say) 1 ms, every server you contact will have a round trip time of at least 102 ms. They *may* have more than this, but none will ever have less. As the day progresses and various groups pop on and off the system in your state, the usage of the upstream and downstream channels changes. It is not unreasonable to guess that both change as a percentage. If that guess is correct, your upstream varies by significantly more than your downstream. That will get into NTPâs loop correction stuff as well. You *might* ask, how about pings? Well, you *might* look into it and find that your local cable system recognizes pings at a very low level and preferentially routes them. Yes, thatâs hogwash and nobody would ever do it â¦.. except thatâs the way it works here with my internet. The network can be completely dead and pings (along with other ICMP traffic) will get through. Hmmmâ¦.. You are indeed a guy with 5 watches to check against. The gotcha is that every single one of them has been set fast or slow by the same amount. Bob On Oct 6, 2016, at 11:03 AM, Chris Albertson wrote: I still think NTP can detect asymmetric delays. Only it can't know that is what it is detecting. What else generate those offset numbers? Yes it could very well be that MRS is running slow but I doubt that is the case. And I really doubt your GPS' PPS is off by even one microsecond. A good bet is that ALL the results we see is because the real-world communication path is different from the assumption NTP makes about communications paths. In practice what NTP sees is all due to the Internet and not so much the reference clocks. Your data shows this. 162.23.41.10 .MRS has different stat depending on who is looking at it. So those billboards are showing network stats not server stats. (but NTP can't know that for certain so it is obliged to call them server stats) This is 2016. Almost any reference clock you are likely to use will be pretty much dead-on, at least to within the precision that NTP works with. So anything those billboards say is really about the communications paths. But NTP has no theoretical right to assume the cause of what it sees. Theory and practice differs, In theory NTP can not detect asymmetric delay but in practice that is about all it detects Maybe I should say NTP detects asymmetric delay jus
[time-nuts] HP59309A gone
___ 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.
Re: [time-nuts] ntp and asymmetric delays
t...@westwood-tech.com said: > I was going to post my ntp output and ask for an opinion, then this > discussion popped up. It would appear that asymmetric delays are the exact > explanation for what I am seeing. Is that a reasonable assumption? It does > seem to be rather consistent throughout the day, however. The reason for > checking against the net when I have a GPS source is that I want ntp to > continue if/when there is no PPS. Is there any way to inform ntp of the > asymmetry? There are 3 sources of offset that I know about. There is the hardware level. If the upload and download speeds differ, that will introduce an offset. You can do the arithmetic to work out how much. (You need to know the length of the packet. I don't have it handy.) The outbound and return paths can be different. That is more likely if the server is farther away. When that happens, the offset will be constant. You can usually see occasional steps in the offset if you watch for several days when the routing changes. Sometimes you have to watch for longer. There are also queuing delays. Bufferbloat is the extreme version of this. You can usually find a minimum of the offset and the offset beyond that is normally noisy. I don't know of any way to tell ntpd about the offset for network packets. (There is a way for local refclocks.) -- These are my opinions. I hate spam. ___ 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.
[time-nuts] Anyone looking for HP 5060A parts/modules?
Hello time-nuts, I have acquired three boxes of modules and parts to Hewlett-Packard 5060A cesium standards. As I don't have one of these units they are excess to my needs. Don't know if anyone still has one of these units ticking as they are quite old and cesium tubes have probably long expired. However, if you do have a need let me know and I will see if I can help. Please contact me off lest. Regards, Skip Withrow ___ 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.
[time-nuts] HP59309A clock that you found?
Hi Bert, Yes, I am interested if you are willing to part with it, I will give it a very good home and even use the HP-IB for backup wall clock time when reading other HP counters. 650.305.0069 and I have a fedex account you would use for shipping if that works for you. Cheers, Bob ___ 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.
Re: [time-nuts] HP 59309A Clock runs, sets via GPIB, but no GPIB output?
Cleaning up I ran across today a HP59309, if some one is interested please contact me off list before I put it on ebay. Bert Kehren In a message dated 10/11/2016 1:54:20 P.M. Eastern Daylight Time, francesco.messi...@gmail.com writes: 1818-2295A dump has been uploaded to ko4bb site, probably there's need to be moved in the right place before it's available. On Mon, Oct 10, 2016 at 9:32 AM, Francesco Messineo wrote: > Hi Dave, > right, once I find the dumps, I'll upload them. > thanks > Frank IZ8DWF > > On Mon, Oct 10, 2016 at 9:24 AM, Artek Manuals wrote: >> Frank >> >> One of the best places to store ROM dumps for easy access by everyon is >> KO4BB.com >> >> Dave >> NR1DX >> dit dit >> >> On 10/10/2016 3:20 AM, Francesco Messineo wrote: >>> >>> I have a dump of the 1818-2295A somewhere, it should be archived in >>> one of my backups. I also made a replacement with a board having 2 x >>> 28C64 SO-28 eeproms and it worked in my 59309A as far as I could test >>> it. However these eeproms present many glitches on the outputs during >>> address toggling, so it's way better to use a suitable CPLD after >>> recovering the equations (I'm a bit stuck on this project due to lack >>> of time...). >>> If someone needs the dump, just let me know and I'll dig it out. >>> HTH >>> Frank IZ8DWF >> >> >> >> -- >> Dave >> manu...@artekmanuals.com >> www.ArtekManuals.com >> ___ >> 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. ___ 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. ___ 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.
Re: [time-nuts] New PPB rated TCXO
On 10/11/16 8:38 AM, Scott Stobbe wrote: This is also showed up on a recent EDN "feature" http://www.edn.com/design/analog/4442801/1/MEMS-oscillator-reduces-dropped-calls-in-base-stations " archaic Quartz oscillator solutions." love it. ___ 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.
Re: [time-nuts] HP 59309A Clock runs, sets via GPIB, but no GPIB output?
1818-2295A dump has been uploaded to ko4bb site, probably there's need to be moved in the right place before it's available. On Mon, Oct 10, 2016 at 9:32 AM, Francesco Messineo wrote: > Hi Dave, > right, once I find the dumps, I'll upload them. > thanks > Frank IZ8DWF > > On Mon, Oct 10, 2016 at 9:24 AM, Artek Manuals > wrote: >> Frank >> >> One of the best places to store ROM dumps for easy access by everyon is >> KO4BB.com >> >> Dave >> NR1DX >> dit dit >> >> On 10/10/2016 3:20 AM, Francesco Messineo wrote: >>> >>> I have a dump of the 1818-2295A somewhere, it should be archived in >>> one of my backups. I also made a replacement with a board having 2 x >>> 28C64 SO-28 eeproms and it worked in my 59309A as far as I could test >>> it. However these eeproms present many glitches on the outputs during >>> address toggling, so it's way better to use a suitable CPLD after >>> recovering the equations (I'm a bit stuck on this project due to lack >>> of time...). >>> If someone needs the dump, just let me know and I'll dig it out. >>> HTH >>> Frank IZ8DWF >> >> >> >> -- >> Dave >> manu...@artekmanuals.com >> www.ArtekManuals.com >> ___ >> 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. ___ 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.
Re: [time-nuts] ntp and asymmetric delays
I was going to post my ntp output and ask for an opinion, then this discussion popped up. It would appear that asymmetric delays are the exact explanation for what I am seeing. Is that a reasonable assumption? It does seem to be rather consistent throughout the day, however. The reason for checking against the net when I have a GPS source is that I want ntp to continue if/when there is no PPS. Is there any way to inform ntp of the asymmetry? Thanks, -- Thomas Valerio Every 20.0s: /usr/sbin/ntpq -n -c pe pe Tue Oct 11 12:37:33 2016 remote refid st t when poll reach delay offset jitter == x127.127.28.0.NMEA. 0 l4 16 3770.000 -30.300 36.009 *127.127.28.1.PPS.0 l3 16 3770.0000.001 0.000 -208.53.158.34 216.93.242.123 u9 64 377 17.2022.907 0.188 +208.100.4.52216.86.146.462 u 64 64 377 16.6122.332 0.193 +208.69.120.241 142.66.101.132 u5 64 377 24.2581.688 0.223 -128.118.25.3130.207.244.240 2 u 53 64 377 40.4294.956 2.577 > Hi > > NTP can *not* detect âcommon modeâ asymmetric delay. Having a local > GPS does not count in this respect. What does count is an NTP client / > server sitting in your home trying to figure out what time it is only > by hooking to the internet. > >To do this it must do a few things: > > 1) Get a signal out through the (slow / long lag) upload channel on your modem. > 2) Route that signal through the cable guyâs low capacity upstream network to >one of his (at best) two or three gateways to your local empire. These may >or may not be in the same state you live in. > 3) Fly the signal over the backbone to whatever server is involved. > 4) Fly a signal back over the backbone to possibly another set of gateways. > 5) Route that signal through the cable guyâs high capacity downstream network. > 6) Run it through the (quite fast / low lag) downstream channel on your modem. > > Steps 1,2,5 and 6 are common to every single server you try to access. If your > modem has an âupstreamâ lag of (say) 101 ms and a âdownstreamâ lag > of (say) 1 ms, every server you contact will have a round trip time of at > least 102 ms. They *may* have more than this, but none will ever have less. > > As the day progresses and various groups pop on and off the system in your state, > the usage of the upstream and downstream channels changes. It is not unreasonable > to guess that both change as a percentage. If that guess is correct, your upstream > varies by significantly more than your downstream. That will get into NTPâs loop > correction stuff as well. > > You *might* ask, how about pings? Well, you *might* look into it and find that > your local cable system recognizes pings at a very low level and preferentially > routes them. Yes, thatâs hogwash and nobody would ever do it â¦.. except > thatâs the way it works here with my internet. The network can be completely > dead and pings (along with other ICMP traffic) will get through. Hmmmâ¦.. > > You are indeed a guy with 5 watches to check against. The gotcha is that every > single one of them has been set fast or slow by the same amount. > > Bob > >> On Oct 6, 2016, at 11:03 AM, Chris Albertson >> wrote: >> >> I still think NTP can detect asymmetric delays. Only it can't know that >> is >> what it is detecting. What else generate those offset numbers? Yes >> it >> could very well be that MRS is running slow but I doubt that is the >> case. >> And I really doubt your GPS' PPS is off by even one microsecond.A >> good >> bet is that ALL the results we see is because the real-world >> communication >> path is different from the assumption NTP makes about communications >> paths. >> >> In practice what NTP sees is all due to the Internet and not so much the >> reference clocks. Your data shows this. 162.23.41.10 .MRS has >> different >> stat depending on who is looking at it. So those billboards are showing >> network stats not server stats. (but NTP can't know that for certain so >> it >> is obliged to call them server stats) >> >> This is 2016. Almost any reference clock you are likely to use will be >> pretty much dead-on, at least to within the precision that NTP works >> with. >> So anything those billboards say is really about the communications >> paths. >> But NTP has no theoretical right to assume the cause of what it sees. >> Theory and practice differs, In theory NTP can not detect asymmetric >> delay but in practice that is about all it detects Maybe I should say >> NTP >> detects asymmetric delay just like the speedometer in my car deters >> engine >> failure. >> >> All that said, if the OP is still reading this it should be very good >> news >> for him because your data shows that NTP can give him his required >> accuracy >> even without
Re: [time-nuts] New PPB rated TCXO
This is also showed up on a recent EDN "feature" http://www.edn.com/design/analog/4442801/1/MEMS-oscillator-reduces-dropped-calls-in-base-stations A Rakon designer chimed in on the comments. On Mon, Oct 10, 2016 at 11:03 AM, Robert LaJeunesse wrote: > For general group information, as SiTime datasheet is not open to the > public (yet?). > > https://www.sitime.com/products/precision-super-tcxo > > Actually a MEMS oscillator, comparison video against quartz TCXO is > interesting. > > Claimed Key Features: > - 30x better dynamic performance for macro cells, small cells, syncE and > optical networks > - 3e-11 Allan Deviation (ADEV) > - 0.2 ps/mv PSNR, eliminating dedicated LDO > - No activity dips or microjumps > - 10x better dynamic stability, replacing OCXOs in IEEE 1588 applications > - 1 to 5 ppb/°C frequency over temperature slope > - -40°C to +105°C operation uniquely enables fan-less outdoor equipment > - 20x greater vibration resistance ensures continuous system operation > > Frequency range 1MHz to 220MHz (via 2 product types) so some form of > synthesizer/divider is inherent. > > Bob L. > ___ > 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. > ___ 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.
[time-nuts] Austron and GPIB gone
___ 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.
Re: [time-nuts] New PPB rated TCXO
If you have a legitimate application for the part, and some volume associated with the application, and you convince their sales person of that, then the data sheets are made available. --- Graham On Tue, Oct 11, 2016 at 8:01 AM, jimlux wrote: > On 10/10/16 11:27 PM, djl wrote: > >> But how the heck did they get some? According to the website, even data >> sheets are not available. >> Don >> > > It's not unusual for one to be able to get small quantities of a > pre-release product if you have a relationship with the manufacturer/sales > engineers. Typically it's bound up with an NDA, and the datasheet is NDA, > and you basically have an agreement that if it turns out poorly so they can > redesign/retool/fix it, you tell the mfr about it, and don't go > broadcasting to the world that this new part is junk. > > In otherwords, not everything is available through distribution and > mail-order. > > This is one of the arguments I make as to why attending in-person > conferences is a good thing - that's how you make those personal > connections. > > > ___ > 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. > ___ 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.
Re: [time-nuts] New PPB rated TCXO
On 10/10/16 11:27 PM, djl wrote: But how the heck did they get some? According to the website, even data sheets are not available. Don It's not unusual for one to be able to get small quantities of a pre-release product if you have a relationship with the manufacturer/sales engineers. Typically it's bound up with an NDA, and the datasheet is NDA, and you basically have an agreement that if it turns out poorly so they can redesign/retool/fix it, you tell the mfr about it, and don't go broadcasting to the world that this new part is junk. In otherwords, not everything is available through distribution and mail-order. This is one of the arguments I make as to why attending in-person conferences is a good thing - that's how you make those personal connections. ___ 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.
[time-nuts] OCXO and GPIB
Downsizing after my move many items have ended up in the trash. Some will go on ebay and some I have given away for the cost of shipping on time nuts. Here are two more. Response please off list. National Instruments GPIB-PCI card new Austron 1150 OCXO 5 MHz no EFC tested, will make a nice offset +-2 Hz for dual mixer. Tested have two one opened was looking for EFC. Bert Kehren ___ 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.
Re: [time-nuts] New PPB rated TCXO
On Mon, Oct 10, 2016 at 11:53 PM, Poul-Henning Kamp wrote: > I take it they know how to price a gem like that ? > > Any ball-park numbers for us ? I don't have any price info for the "Super-TCXO" but I'd be surprised if it were crazy, SiTime's other products are all pretty reasonably priced. On Mon, Oct 10, 2016 at 11:27 PM, djl wrote: > But how the heck did they get some? According to the website, even data > sheets are not available. I imagine they got in touch with the manufacturer via the prominently-displayed email address on the webpage :) Having the prospect of buying at least a few reels' worth probably helped too. Henry ___ 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.