Re: [time-nuts] Symmetricom TS2100-GPS - 1PPS has 10uS offset
Jason Rabel kirjoitti: I think nobody ever really bothered to fix anything since the NTP time was good enough. Yes - definitely... If it's only used for NTP then the 10 usec error is totally insignificiant. NTP solution seems to be quite inaccurate, if I poll my server from http://support.ntp.org/ntpq.php the results can vary couple of milliseconds every time. However the offset shown by test page is always less than 10 milliseconds. Maybe this is because the route is too long: delay is more than 230 ms - the test site is far side of the world for me... It' the nature of the TCP/IP and Internet that the delays are quite random. Same result if I set up software NTP server which polls many NTP servers from the net. The results are always vayring many milliseconds and the server will constantly change the best server to follow. I think the multitasking operating system will also add some errors to the ntp server operation, since the internal system delays will always change as well. The hidden eng menu does have some interesting stuff. I've tweaked the offset to bring time in sync with my other NTP servers, usually around -4000 does the trick since the TS2100 doesn't use a true NTP implementation (I think it is more SNTP). According to manual it should support both protocols, but maybe this NTP vs SNTP is more like client side difference? I understood that NTP polls many servers to get kind of averaged timing, when SNTP uses only one server. For example Windows has SNTP only, you can define only one time server to use at time. Well of course TS2100 doesn't poll any servers and uses only one time source, GPS. I have seen different offset settings in units, so I would think there would be *some* way to save the setting, but like you have not found out a way to do it yet. :( Yes! That's now the only question... If this will remain unknown, then maybe I will setup a microcontroller connected to the console port and set it to follow somehow, when TS2100 is restarted. Then it could send the eng tim offset... command via serial port to restore the offset setting automatically every time when needed. This is quite stupid way to store the setting, but it might be the only way if the offical way to store the settings will remain unknown. -- 73s! Esa OH4KJU ___ 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] OXCO Issues -- Latest
Hi If they are carbon film, I'd look for cracked end terminations. Hopefully the color codes are still readable. That should make the replacement process fairly easy. Another possibility - the thermistor bridge probably is / was regulated. If it's a zener diode, it may have opened up. That would boost the input voltage and increase the effective gain. Bob On May 12, 2013, at 11:36 AM, Frederick Bray fwb...@mminternet.com wrote: Well, I decided to make the Y incision and pulled the circuit board out of the oven. (Photos later after I crop them.) Yes, the trimpot is part of the circuit associated with the thermistor. My plan is to check the resistors (surprisingly most are carbon film except those in the thermistor circuit), look at the circuit board under a magnifier, and stick it back in the foam for testing after making any repairs. Thanks again for the continuing comments and advice. Fred ___ 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] Trimble Resolution T versus Motorola Oncore UT+
because of the long filter time may not even need saw tooth You still have the opportunity for hanging bridges. You may be farther out on the tail of the curve, but the tail is very long. -- 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.
Re: [time-nuts] Symmetricom TS2100-GPS - 1PPS has 10uS offset
On Sun, May 12, 2013 at 1:34 AM, Esa Heikkinen tn1...@nic.fi wrote: Jason Rabel kirjoitti: I think nobody ever really bothered to fix anything since the NTP time was good enough. Yes - definitely... If it's only used for NTP then the 10 usec error is totally insignificiant. A startum one NTP server typically runs with abot 2 uSec error fro UTC. ButA stratum two server, that means one that gets time from the strum one over the network NTP solution seems to be quite inaccurate, if I poll my server from http://support.ntp.org/ntpq.php the results can vary couple of milliseconds every time. Most Statum One NTP server are better then 10 uSec. 2 uSec is about what you should shoot for. It shouldn't work that way. What NTP does is discipline a local clock. It take hours or days before it settles and a lot depends on how good the local oscillator is. Mostly your local oscillator is just a TTL can that cost about 50 cents solder to a PC mother board. The the error in one poll does not matter to much because hundreds of them will be done and NTP wil make tiny adjustments to the locals clock's RATE. NTP is not adjusting the time, it adjusts the rate. (OK there is one time exception if the time is found to tbe far off) It does not do an adverse of servers. It compares them to find the best subset. This stops a broken server from polluting the average. Yes there might be a 10ms error in a polled time Bt what NTP is doing is noteing the local time, letting the local clock run for say 20 minutes then comparing to the server(s) to see if the local clock is fast or slow. So that 10ms error is only parts per million. It is not a 10ms absolute error in UTC time. If your local oscillator were better then NTP would open up that 20 minutes window and if the results aren't good it closes it down. It tries to keep several of those 20 minute intervals open at once. On the other hand SMTP, to thing that Windows uses simply gets the time and jumps the local clock to match and that's it. It does not discipline the rate. SNTP is a one-time thing -- 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] Trimble Resolution T versus Motorola Oncore UT+
On 13/05/13 00:13, Bob Camp wrote: Hi Is the M12 going away or they just going through (another) parts change? You are correct. I read it sloppy, but I did recall that there was something going on (easy to check by just reading the link I did provide - so brown paper bag on my head this time). Regardless, one has to be a bit careful in expected lifetime. Cheers, Magnus Bob On May 12, 2013, at 5:15 PM, Magnus Danielsonmag...@rubidium.dyndns.org wrote: Hi Bert, On 12/05/13 22:31, ewkeh...@aol.com wrote: With the availability of Motorola Oncore products and the Synergy pin compatible it would make sense that some one does a board design that allows plug in and saw tooth correction. We use a 14 pin PIC and a DS 1023 with good results. Should also add a survey command. With the increasing cost of Tbolts this is a nice alternative. The latest Shera makes it a nice GPSDO for OCXO's and Rb's. The list price for a DS 1023 is just at $ 19 (lot of silicon) but if some one does a group buy if the interest is there a $ 25 kit price would be attainable. Right now I found a source $ 10 plus shipping I paid just over $ 6, three month ago. using one of these in a Rb application because of the long filter time may not even need saw tooth If it where that simple. Regarding availability of the iLotus M12M see this on Synergy: http://www.synergy-gps.com/index.php?option=com_contenttask=viewid=104Itemid=138 Availability: Get it while you can, it's going away. It looks like you will have to consider using LEA6T or something like that soon enough. I like the openness of the Motorola and Novatel receivers. Which modern receivers provide the same level of openness into states and details? Oh, we should make sure to backup documentation on the Oncores. The early ones is already fuzzy. Cheers, Magnus ___ 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] OXCO Issues -- Latest
My guess is that there is a 'test case' that the unit (foam enclosed units minus the metal case) is placed into that has a hole through which adjustments can be made. Then, it is removed and installed in its 'final resting place' before sealing the unit. Joe -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Don Latham Sent: Sunday, May 12, 2013 5:16 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] OXCO Issues -- Latest If there's a pot set that's inside the case, indeed inside the foam then there has to be a procedure for setting it before final assembly, no? can't believe an engineering setup that requires tiny tweaks with assembly and disassembly. . . Don Bob Camp Hi Several outfits made pot set OCXO's for a *long* time. As far as I know there isn't any sort of premature end of life situation with those designs. Bob On May 12, 2013, at 3:40 PM, Al Wolfe alw.k...@gmail.com wrote: Years ago we were taught that it was poor engineering practice to use pots to trim a DC value, especially if any appreciable current was to be drawn from the wiper. (Probably true for any kind of signal on a pot) It seems that current through the wiper would eventually erode away the material under the wiper. This is true especially for set-and-forget applications. If the wiper is used only as a voltage reference and very little current drawn then it is probably OK for most situations. The above info is mainly for carbon and ceramic pots. Wire wound ones tend to be somewhat more forgiving but they tend to be step-variable between the wire turns. Often the sweet spot is between the steps and they aren't very useful for fine tuning purposes. Sometimes we would use two pots in series. One was set up as a rheostat and was around 5 percent of the ohmage of the main one. It was used for fine tuning but the problem of DC current through the wiper remains and is exacerbated. Probably the best design is to use fixed resistors for most of the voltage divider circuit and the variable element be a small fraction of the total divider resistance. Al Well, I decided to make the Y incision and pulled the circuit board out of the oven. (Photos later after I crop them.) Yes, the trimpot is part of the circuit associated with the thermistor. My plan is to check the resistors (surprisingly most are carbon film except those in the thermistor circuit), look at the circuit board under a magnifier, and stick it back in the foam for testing after making any repairs. Thanks again for the continuing comments and advice. Fred ___ 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. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. De Erroribus Medicorum, R. Bacon, 13th century. If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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.
