Re: [time-nuts] Symmetricom TimeSource 2700
Hi The upstream time source may or may not be very good. Since it's PCS at 1.9 GHz and not 900 MHz CDMA, the carriers have a lot of wiggle room. You can go in and fiddle which signal it tracks. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Tuesday, May 01, 2012 12:41 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Symmetricom TimeSource 2700 Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer --- On Thu, 11/24/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Thursday, November 24, 2011, 11:17 PM Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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] Symmetricom TimeSource 2700
The problem is I don't have the software for the unit, but based on the behaviour of the alarm and status led's I'm confident it is locked. The symmetricom site may have the software but I would need to agree to an eula prior to downloading which I don't want to do with my work account. So far symmetricom hasn't approved my request for a personal log in to their site. I may try again with another email address (: -- On Tue, 1 May, 2012 2:31 PM EDT Bob Camp wrote: Hi The upstream time source may or may not be very good. Since it's PCS at 1.9 GHz and not 900 MHz CDMA, the carriers have a lot of wiggle room. You can go in and fiddle which signal it tracks. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Spencer Sent: Tuesday, May 01, 2012 12:41 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Symmetricom TimeSource 2700 Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer --- On Thu, 11/24/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Thursday, November 24, 2011, 11:17 PM Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https
Re: [time-nuts] Symmetricom TimeSource 2700
Hello Mark, you could connect the Fury 1PPS output to the 1PPS external sync input of the PRS-10 Rb and let is self-discipline to GPS. Set the Fury 1PPS jumper JP4 to raw-1PPS (pins 2 and 3), and that will make the Fury GPSDO generate the raw 1PPS signal from the Motorola GPS receiver albeit without sawtooth correction. You won't need sawtooth correction if you set the PRS-10 time constant to say 10,000 seconds. bye, Said In a message dated 5/1/2012 10:55:34 Pacific Daylight Time, mspencer12...@yahoo.ca writes: Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer ___ 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 TimeSource 2700
I am playing around with a OT-20 Office Time that I pulled out of a dumpster some time ago. I've only just powered it up last weekend and it without an antenna will illuminate its CDMA green status LED in about 10 minutes. I've not tried an antenna or hooked up a terminal to its serial port. -pete On Tue, May 1, 2012 at 9:40 AM, Mark Spencer mspencer12...@yahoo.ca wrote: Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer --- On Thu, 11/24/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Thursday, November 24, 2011, 11:17 PM Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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] Symmetricom TimeSource 2700
Thought the cdma signals were all gone. On Tue, May 1, 2012 at 6:50 PM, Pete Lancashire p...@petelancashire.comwrote: I am playing around with a OT-20 Office Time that I pulled out of a dumpster some time ago. I've only just powered it up last weekend and it without an antenna will illuminate its CDMA green status LED in about 10 minutes. I've not tried an antenna or hooked up a terminal to its serial port. -pete On Tue, May 1, 2012 at 9:40 AM, Mark Spencer mspencer12...@yahoo.ca wrote: Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer --- On Thu, 11/24/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Thursday, November 24, 2011, 11:17 PM Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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
Re: [time-nuts] Symmetricom TimeSource 2700
Hi CDMA is very much alive and kicking in the US. Bob On May 1, 2012, at 7:00 PM, paul swed wrote: Thought the cdma signals were all gone. On Tue, May 1, 2012 at 6:50 PM, Pete Lancashire p...@petelancashire.comwrote: I am playing around with a OT-20 Office Time that I pulled out of a dumpster some time ago. I've only just powered it up last weekend and it without an antenna will illuminate its CDMA green status LED in about 10 minutes. I've not tried an antenna or hooked up a terminal to its serial port. -pete On Tue, May 1, 2012 at 9:40 AM, Mark Spencer mspencer12...@yahoo.ca wrote: Sorry to resurrect an old thread, but I thought someone might find this of interest. I purchased a 2700 intending to harvest the PRS10. Prior to cracking open the case I powered up the unit to ensure it was basically working so I could return it if needed. I noticed that despite not having an antenna connected it seemed to find and track CDMA signals and after a few hours the 10 Mhz output was in a few parts of 10E-12 of my GPSD0. After a bit of investigation I found the following Adding an external antenna didn't seem to make much difference to the performance. The 1pps output is approx. 75ms out of sync with the 1pps output from my Fury GPSD0. From time to time the 10 Mhz output experiences phase jumps of several tens of ns. Manipulating the unit (ie. connecting to the RS 422 port) may induce this. Power cycling the unit seems to cure the problem and the unit usually takes an hour or two to re lock. It's possible that the lack of a proper ground in my instalation may be causing some of the issues as well. This problem would be a show stopper for me in terms of using this unit to replace my GPSDO's. I'm not sure if this issue is specfic to my unit or not. I've attached some initial ADEV plots showing the typical performance of the 10 Mhz output vs three of my other references. (I wouldn't put a lot of emphasis on the results of taus of less than 100 seconds or more than 6,000 or so..) I doubt I'm going to put much more time into this unit but it's an interesting novelty in it's original state. The results of other units may well differ (: Regards Mark Spencer --- On Thu, 11/24/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Thursday, November 24, 2011, 11:17 PM Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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
Re: [time-nuts] Symmetricom TimeSource 2700
I don't know how (or if) they deal with the distance from the cell. The accuracy of the PPS signal from CDMA time receivers is usually specified as no better than 10 microseconds or so, so they may just assume the cell tower is close enough not to make it worse than 10 microseconds. I'm pretty sure at least some systems have something much better than that. The FCC requires some sort of pretty good location reporting for 911. I think the requirement is something like better than 100 yards more than 95% of the time. The cell phone companies can do it any way they want. GPS is one choice. Another is triangulation from cell towers. 100 meters is 300 ns which is a lot less than 10 microseconds. -- These are my opinions, not necessarily my employer's. 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 TimeSource 2700
It's been a while, but from what I remember the sync channel message does indeed include the system time (which is the same as GPS time with a UTC offset) and also the PN code offset that this cell is using. This leaves the only remaining unknown as the path delay to the cell and the possible error in the local clock on the BTS. The other possible source of error is that if one of the sites loses GPS lock, it will flywheel - this will generate a yellow alarm, but this is not communicated over the air interface - I suspect that the largest component of that stated 10uS maximum timing error is based on worse-case accumulated phase error. I also suspect this is why that Symmetricom box is tracking multiple pilots, so it can isolate and discard any that appear to be significantly out. Regards, Pete On Wed, Nov 30, 2011 at 1:37 PM, Dennis Ferguson dennis.c.fergu...@gmail.com wrote: I think they track both the CDMA pilot and sync channels. The latter channel sends a message which tells the phone about the cell, and gives gives the phone enough information to figure out the time of day. I'm pretty sure CDMA phones have to know what time it is before they register with the cell. To receive the paging channel and negotiate a registration the phone has to receive and send the long code chip sequence, which I think is 2^40 bits long and takes more than a month to repeat. The phone has to know what time it is before it has any hope of tracking that. I don't know how (or if) they deal with the distance from the cell. The accuracy of the PPS signal from CDMA time receivers is usually specified as no better than 10 microseconds or so, so they may just assume the cell tower is close enough not to make it worse than 10 microseconds. Dennis Ferguson On 29 Nov, 2011, at 18:54 , Peter Bell wrote: Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone can do it, since it can ask transmit back to the BTS and measure the round trip timing offset). ___ 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] Symmetricom TimeSource 2700
Yes, you are correct. 10 microseconds comes directly from the CDMA spec, it is the amount of time the reference at a base station is allowed to drift when it is in holdover before it is out of spec and needs to be removed from service. I still don't know what they do about path delay since (as you point out) I believe this can be measured only after a handset has registered with the tower, and the timing receivers never register. And the path delay can be quite large if you live far enough away from civilization. When I take my Verizon phone to Toronto it often registers with a Verizon tower which must be at least 20 miles away (i.e. the width of the lake). If that was the distance to the only tower the timing receiver had to listen to that would be more than 100 microseconds of delay, and I don't see how it could correct that. Dennis Ferguson On 30 Nov, 2011, at 02:42 , Peter Bell wrote: It's been a while, but from what I remember the sync channel message does indeed include the system time (which is the same as GPS time with a UTC offset) and also the PN code offset that this cell is using. This leaves the only remaining unknown as the path delay to the cell and the possible error in the local clock on the BTS. The other possible source of error is that if one of the sites loses GPS lock, it will flywheel - this will generate a yellow alarm, but this is not communicated over the air interface - I suspect that the largest component of that stated 10uS maximum timing error is based on worse-case accumulated phase error. I also suspect this is why that Symmetricom box is tracking multiple pilots, so it can isolate and discard any that appear to be significantly out. Regards, Pete On Wed, Nov 30, 2011 at 1:37 PM, Dennis Ferguson dennis.c.fergu...@gmail.com wrote: I think they track both the CDMA pilot and sync channels. The latter channel sends a message which tells the phone about the cell, and gives gives the phone enough information to figure out the time of day. I'm pretty sure CDMA phones have to know what time it is before they register with the cell. To receive the paging channel and negotiate a registration the phone has to receive and send the long code chip sequence, which I think is 2^40 bits long and takes more than a month to repeat. The phone has to know what time it is before it has any hope of tracking that. I don't know how (or if) they deal with the distance from the cell. The accuracy of the PPS signal from CDMA time receivers is usually specified as no better than 10 microseconds or so, so they may just assume the cell tower is close enough not to make it worse than 10 microseconds. Dennis Ferguson On 29 Nov, 2011, at 18:54 , Peter Bell wrote: Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone can do it, since it can ask transmit back to the BTS and measure the round trip timing offset). ___ 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] Symmetricom TimeSource 2700
Hi Charles, Thanks very much for the information on the pinout of the TOD connector on the TS2700. I verified the PPS signal between pins 6 and 1. It's duration and voltage matches your report. I compared the timing of the PPS signal with the PPS of two synchronized thunderbolts. Interesting, the PPS signal from the TS2700 is delayed a rather constant 280ms compared to the two TBolts over about a minute of observation. One reason why I'm interested in the PPS output is to provide a varied NTP source for my Soekris 4501s. I have TBolts, M12M, Netclock/2 WWVB, and Garmin 18x. I thought it's be nice to have a CDMA clock as well. If of the PPS offset remains a constant, then I could use the TS2700 as an NTP reference clock. (I realize I'd have to write an NTP driver for the device). But, the fact that the TS2700 is a 1/4 sec off of GPS PPS makes me suspicious that the device was never interested to provide a precise PPS -- just a reference frequency source as advertised. Anyway, many thanks for all your help in understanding the device. I'll report more if I learn anything interesting. Kevin ___ 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 TimeSource 2700
Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone On Wed, Nov 30, 2011 at 3:06 AM, Kevin Rosenberg ke...@rosenberg.net wrote: Hi Charles, Thanks very much for the information on the pinout of the TOD connector on the TS2700. I verified the PPS signal between pins 6 and 1. It's duration and voltage matches your report. I compared the timing of the PPS signal with the PPS of two synchronized thunderbolts. Interesting, the PPS signal from the TS2700 is delayed a rather constant 280ms compared to the two TBolts over about a minute of observation. One reason why I'm interested in the PPS output is to provide a varied NTP source for my Soekris 4501s. I have TBolts, M12M, Netclock/2 WWVB, and Garmin 18x. I thought it's be nice to have a CDMA clock as well. If of the PPS offset remains a constant, then I could use the TS2700 as an NTP reference clock. (I realize I'd have to write an NTP driver for the device). But, the fact that the TS2700 is a 1/4 sec off of GPS PPS makes me suspicious that the device was never interested to provide a precise PPS -- just a reference frequency source as advertised. Anyway, many thanks for all your help in understanding the device. I'll report more if I learn anything interesting. Kevin ___ 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] Symmetricom TimeSource 2700
Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone can do it, since it can ask transmit back to the BTS and measure the round trip timing offset). If you had access to the AGPS dats from the BTS, you could in principle get a position fix from it and calculate the offset that way - but when I played with this a few years ago, I couldn't find any way to get that data from the system unless you were registered - and, obviously, that is not something you can do just using a receiver. Regards, Pete On Wed, Nov 30, 2011 at 3:06 AM, Kevin Rosenberg ke...@rosenberg.net wrote: Hi Charles, Thanks very much for the information on the pinout of the TOD connector on the TS2700. I verified the PPS signal between pins 6 and 1. It's duration and voltage matches your report. I compared the timing of the PPS signal with the PPS of two synchronized thunderbolts. Interesting, the PPS signal from the TS2700 is delayed a rather constant 280ms compared to the two TBolts over about a minute of observation. One reason why I'm interested in the PPS output is to provide a varied NTP source for my Soekris 4501s. I have TBolts, M12M, Netclock/2 WWVB, and Garmin 18x. I thought it's be nice to have a CDMA clock as well. If of the PPS offset remains a constant, then I could use the TS2700 as an NTP reference clock. (I realize I'd have to write an NTP driver for the device). But, the fact that the TS2700 is a 1/4 sec off of GPS PPS makes me suspicious that the device was never interested to provide a precise PPS -- just a reference frequency source as advertised. Anyway, many thanks for all your help in understanding the device. I'll report more if I learn anything interesting. Kevin ___ 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] Symmetricom TimeSource 2700
I think they track both the CDMA pilot and sync channels. The latter channel sends a message which tells the phone about the cell, and gives gives the phone enough information to figure out the time of day. I'm pretty sure CDMA phones have to know what time it is before they register with the cell. To receive the paging channel and negotiate a registration the phone has to receive and send the long code chip sequence, which I think is 2^40 bits long and takes more than a month to repeat. The phone has to know what time it is before it has any hope of tracking that. I don't know how (or if) they deal with the distance from the cell. The accuracy of the PPS signal from CDMA time receivers is usually specified as no better than 10 microseconds or so, so they may just assume the cell tower is close enough not to make it worse than 10 microseconds. Dennis Ferguson On 29 Nov, 2011, at 18:54 , Peter Bell wrote: Assuming it's just tracking the CDMA pilots, the 1PPS output is likely not aligned with UTC. The problem is that the pilot channel is just a PN sequence with no modulating data - so when you lock to it you can know that your local clock is 19200Hz * 64 chips/bit (1.228MHz) - but that's all you know. Even the code phase doesn't tell you anything, since there are two unknowns - the first is the distance to the cell and the second is the code phase offset on this specific pilot (each BTS has it's modulating sequence offset by an integer multiple of 64 chips to reduce mutual interference) - the second piece of information you can obtain by reading one of the overhead channels, but the first is basically not available just using a receiver (your phone can do it, since it can ask transmit back to the BTS and measure the round trip timing offset). ___ 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 TimeSource 2700
I wrote: pretty much every BTMon window contains a TOD display. I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. Best regards, Charles ___ 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 TimeSource 2700
Thanks for that information. I had assumed that it was obtained from the cell towers -- after all, my cellphone does show local time. I was hoping that there would be a TOD output. Still the device is very nice and useful as a frequency standard. On 11/24/2011 8:25 AM, Charles P. Steinmetz wrote: I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. ___ 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 TimeSource 2700
Frederick wrote: Thanks for that information. I had assumed that it was obtained from the cell towers I was hoping that there would be a TOD output. Still the device is very nice and useful as a frequency standard. Symmetricom sold the TS2700 as a Stratum 1 source, so it is likely that TOD information is available from the unit -- my point was just that it does not seem to appear on the Craft output, which is used for monitoring the 2700. p.21 of the manual describes the T1 outputs: The Ensemble Timing Generator provides the timing for the T1 timing signals available at the Output Span A and B connectors in a framed, all-ones format, which is selectable in either D4 or ESF framing. SSM is available with ESF framing. p.21 also describes the 10 MHz output: The Ensemble Timing Generator provides the timing for the 10 MHz low-phase-noise timing signal, available at the 10 MHz Output connector, which can be used for local cellular frequency or testing purposes. It seems clear that Symmetricom does not consider the 10 MHz output to be the TS2700's primary output. Best regards, Charles ___ 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 TimeSource 2700
On Nov 24, 2011, at 9:25 AM, Charles P. Steinmetz wrote: I did a little investigating, and it turns out that the TOD displayed in the BTMon windows is the local system time, NOT time received from the TS2700. Apparently, the TS2700 does not send TOD on the Craft output. Hi Charles, When I first used BTMon, I wondered if that was the case. However, reading more about the TL1 messages from the Craft output, there are messages for date and time: date: This parameter is the current date in the 8-digit form -mm-dd, where is year, mm is month (01–12), and dd is day (01–31). time: This parameter is the current time in the 6-digit form hh-mm-ss where hh is hours (0–23), mm is minutes (0–59), and ss is seconds (0–59). The factory setting is GMT for local time. Assuming your investigation is connect, then system time is used in BTMon windows, but it's also documented to be present on the Craft output. For my next investigation, I need to read a bit on RS-422/485 pinouts on a DE-9 connector. I think I have a Maxim sample RS-485 transceiver I can use to look at data on the TOD output. Also, once I know the pinout, I'll know where ground is and can look for a PPS on one of the other pins. If I don't get far there, then I was thinking about looking at the 2 Hz test point and seeing if that's synchronized to a GPS PPS signal. Thanks for information! Kevin ___ 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 TimeSource 2700
Kevin wrote: reading more about the TL1 messages from the Craft output, there are messages for date and time: date: This parameter is the current date in the 8-digit form -mm-dd, where is year, mm is month (0112), and dd is day (0131). time: This parameter is the current time in the 6-digit form hh-mm-ss where hh is hours (023), mm is minutes (059), and ss is seconds (059). The factory setting is GMT for local time. Right. However, the manual does not say that these are sent regularly (every second, or whatever). Note that date and time are both reported as parameters in each Alarm and Event message. So are ocrdat and ocrtm (date and time, respectively, when the event occurred). The Craft output feeds a PC Com port -- I'd think that reading the Com port with a terminal emulator should verify whether the date and time events are sent regularly, or only with Alarms or Events. Best regards, Charles ___ 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 TimeSource 2700
I wrote: The Craft output feeds a PC Com port -- I'd think that reading the Com port with a terminal emulator should verify whether the date and time events are sent regularly, or only with Alarms or Events. I just did this, and the TS2700 has been silent for 30 minutes (it has not had an Alarm or Event since its last power cycle, about 6 months ago, according to its log). I did not want to disturb it by creating an Alarm or Event. However, I tested the terminal emulator by switching the COM port to a TBolt, and confirmed that the TBolt is very chatty. So: I conclude that the TS2700 sends time and date information to the Craft output only as parameters in Alarm and Event messages, not as independent events (at least not more frequently than once in 1/2 hour). Best regards, Charles ___ 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 TimeSource 2700
On Nov 24, 2011, at 2:43 PM, Charles P. Steinmetz wrote: I just did this, and the TS2700 has been silent for 30 minutes (it has not had an Alarm or Event since its last power cycle, about 6 months ago, according to its log). I did not want to disturb it by creating an Alarm or Event. However, I tested the terminal emulator by switching the COM port to a TBolt, and confirmed that the TBolt is very chatty. So: I conclude that the TS2700 sends time and date information to the Craft output only as parameters in Alarm and Event messages, not as independent events (at least not more frequently than once in 1/2 hour). Thanks for the report on that, Charles. I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. Best, Kevin ___ 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 TimeSource 2700
Kevin wrote: I use the Craft connector for monitoring with BTMon rather than the RS-232 port. It appears the Craft output, while spontaneously emitting alarm/events, does respond to queries from BTMon on the Craft input. Everything I reported previously involved the Craft port feeding a PC COM port using the RJ45-to-DB9 cable supplied by Symmetricom. Do you happen to have a RS-422/485 interface? I don't, but I'm interested to see if any spontaneous output occurs on the TOD port. I have a 422/485 card here somewhere, but I haven't used it (maybe even seen it) in more than 10 years. I poked a scope at the TOD jack. The TS2500 manual says that (in a TS2500) Pin 1 should be PPS (positive), Pin 6 should be PPS (negative), Pin 5 should be TXA output (positive), Pin 9 should be TXA output (negative), and Pins 7 and 3 should be a 20 V external supply positive and return, respectively. I found PPS positive and negative on Pins 1 and 6. Logic low is about 1.2 V positive with respect to case ground, and logic high is about 3.8 V above case ground, for a logic range of approximately 2.6 V. The PPS pulses are 500 uS wide with rise and fall times of ~20-25 nS. I did not see any data on the TXA outputs -- the positive TXA output just sits at logic low and the negative TXA output sits at logic high. There is 20 V between Pins 7 and 3. As for the unspecified pins -- Pin 2 sits at nominally 0 Vdc, and Pins 4 and 8 sit at nominally 0.168 Vdc. All three have around 20 mVp-p of hum and noise. While I was at it, I poked at the RS232 connector, as well. Pin 3 (TX Data) has a 16 or 17 mS burst of data every 5 seconds (approximately), from -10 V to +10 V with respect to case (henceforth, 232 low and high, respectively). Between bursts, it sits at 232 low. Pins 4 and 7 (DTR and RTS, respectively) sit at 232 high. All other pins sit at ground. Best regards, Charles ___ 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 TimeSource 2700
The TS2500 was a very similar unit that received its timing signals from GPS. I assume they were built on the same case, hence the spare chassis hole (and perhaps also some features in BTMon that are not used by the TS2700). I'm sorry to butt in here, but could you please tell me: Does a TS2500 have an internal PRS-10 too? I've just bought a TS2700 on fleaBay to harvest the PRS-10 from it, as it is pretty useless here in Europe without CDMA network. But a TS2500 may probably do what I had in mind for the PRS-10: To discipline it with a Resolution-T GPS receiver and to use it as a frequency standard for my measurement interface and as a time Stratum 1 time source to my network (with a still-to-purchase NTP server). Cheers, Robert. ___ 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 TimeSource 2700
I'm curious if any one has any specific information about how TOD data could be sent via the native T1 data frames (as opposed to a signal which another piece of equipment could use as a clock source.) I've never seen any specs for sending TOD information via the ESF Data Link or any other means, but that doesn't mean a spec doesn't exist somewhere. --- On Mon, 11/21/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Monday, November 21, 2011, 6:13 PM Kevin wrote: The PPS in/out of the PRS10 do not appear to connected to the TS2700 logic board. I believe the TS2700 does not take PPS timing from the PRS10, nor does it discipline the PRS10. It does, however, keep tabs on the frequency of the PRS10, and I believe it uses this information to generate corrections to the TS2700 frequency and timing outputs during holdover -- that is, I believe it does not just pass through the PRS10 10 MHz signal and derive other timing signals from it during holdover, but applies corrections that it has learned from its monitoring. See the block diagram at p. 19 of the TS2700 manual and text at p. 14. I'm not looking for a PPS that's just a frequency/period reference, but instead places the PPS at the GPS PPS position. Perhaps the TS2700 is already do it, but so far, I've only seed evidence that it's a frequency reference. The whole point of the TS2700 is to be a Stratum 1 time source. See the TS2700 manual at pp. 14 and 113. The TS2700 clearly sends TOD information -- pretty much every BTMon window contains a TOD display. Because the TS2700 was designed for telecommunications central office applications, the main outputs are two T1s, Span A and Span B, rather than computing protocols that would be more familiar to most techies. To access the TOD and timing information, I think you would need to decode the T1 data stream. It may be available at the Craft output, as well -- the TOD data definitely is, but I do not know about the precision timing data. (For those who are curious, Craft is an ancient telecommunications term.) Best regards, Charles ___ 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] Symmetricom TimeSource 2700
Hi There are so many vendor / country specific sub (sub...sub) frames in T1/E1 that there must be at least one that sticks in time of day... Bob Sent from my iPhone On Nov 23, 2011, at 7:01 PM, Mark Spencer mspencer12...@yahoo.ca wrote: I'm curious if any one has any specific information about how TOD data could be sent via the native T1 data frames (as opposed to a signal which another piece of equipment could use as a clock source.) I've never seen any specs for sending TOD information via the ESF Data Link or any other means, but that doesn't mean a spec doesn't exist somewhere. --- On Mon, 11/21/11, Charles P. Steinmetz charles_steinm...@lavabit.com wrote: From: Charles P. Steinmetz charles_steinm...@lavabit.com Subject: Re: [time-nuts] Symmetricom TimeSource 2700 To: Discussion of precise time and frequency measurement time-nuts@febo.com Received: Monday, November 21, 2011, 6:13 PM Kevin wrote: The PPS in/out of the PRS10 do not appear to connected to the TS2700 logic board. I believe the TS2700 does not take PPS timing from the PRS10, nor does it discipline the PRS10. It does, however, keep tabs on the frequency of the PRS10, and I believe it uses this information to generate corrections to the TS2700 frequency and timing outputs during holdover -- that is, I believe it does not just pass through the PRS10 10 MHz signal and derive other timing signals from it during holdover, but applies corrections that it has learned from its monitoring. See the block diagram at p. 19 of the TS2700 manual and text at p. 14. I'm not looking for a PPS that's just a frequency/period reference, but instead places the PPS at the GPS PPS position. Perhaps the TS2700 is already do it, but so far, I've only seed evidence that it's a frequency reference. The whole point of the TS2700 is to be a Stratum 1 time source. See the TS2700 manual at pp. 14 and 113. The TS2700 clearly sends TOD information -- pretty much every BTMon window contains a TOD display. Because the TS2700 was designed for telecommunications central office applications, the main outputs are two T1s, Span A and Span B, rather than computing protocols that would be more familiar to most techies. To access the TOD and timing information, I think you would need to decode the T1 data stream. It may be available at the Craft output, as well -- the TOD data definitely is, but I do not know about the precision timing data. (For those who are curious, Craft is an ancient telecommunications term.) Best regards, Charles ___ 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] Symmetricom TimeSource 2700
On Nov 21, 2011, at 10:33 PM, Charles P. Steinmetz wrote: The TS2500 was a very similar unit that received its timing signals from GPS. I assume they were built on the same case, hence the spare chassis hole (and perhaps also some features in BTMon that are not used by the TS2700). I appreciate that information. It makes such observations less mysterious. Yes, please report your findings on the TOD connector. That connector, and the corresponding feature in the BTMon software, could apply only to versions of the TS2700 with an optional TOD function, or, more likely, to the TS2500 or other model built on the same chassis/motherboard. It will be interesting to see if there is any data there in a TS2700. I took apart the 3 boards of the TS2700. It's really a very beautifully constructed device. Pins on the TOD connector are connected to two MAX490Es (RS-422/485 transceivers). Likely some TOD data is present on TOD connector. I reassembled the TS2700 enough it turn it back on with the Rb. Using BTMon and selecting NTP or Cisco for the TOD, the actual error message affirms your assumption. The message is Incompatible Target Revision, Cannot Configure TOD. I hadn't realized that BTMon was used for other devices. I found labelled test points for 200 Hz, 4 Hz, and 2 Hz on the logic board. I didn't find any pins labelled 1 Hz or PPS. Kevin ___ 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 TimeSource 2700
Kevin wrote: The PPS in/out of the PRS10 do not appear to connected to the TS2700 logic board. I believe the TS2700 does not take PPS timing from the PRS10, nor does it discipline the PRS10. It does, however, keep tabs on the frequency of the PRS10, and I believe it uses this information to generate corrections to the TS2700 frequency and timing outputs during holdover -- that is, I believe it does not just pass through the PRS10 10 MHz signal and derive other timing signals from it during holdover, but applies corrections that it has learned from its monitoring. See the block diagram at p. 19 of the TS2700 manual and text at p. 14. I'm not looking for a PPS that's just a frequency/period reference, but instead places the PPS at the GPS PPS position. Perhaps the TS2700 is already do it, but so far, I've only seed evidence that it's a frequency reference. The whole point of the TS2700 is to be a Stratum 1 time source. See the TS2700 manual at pp. 14 and 113. The TS2700 clearly sends TOD information -- pretty much every BTMon window contains a TOD display. Because the TS2700 was designed for telecommunications central office applications, the main outputs are two T1s, Span A and Span B, rather than computing protocols that would be more familiar to most techies. To access the TOD and timing information, I think you would need to decode the T1 data stream. It may be available at the Craft output, as well -- the TOD data definitely is, but I do not know about the precision timing data. (For those who are curious, Craft is an ancient telecommunications term.) Best regards, Charles ___ 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 TimeSource 2700
On Nov 21, 2011, at 4:13 PM, Charles P. Steinmetz wrote: The whole point of the TS2700 is to be a Stratum 1 time source. See the TS2700 manual at pp. 14 and 113. The TS2700 clearly sends TOD information -- pretty much every BTMon window contains a TOD display. Hi Charles, Thanks very much for the information and your insights. Much appreciated. Your point above is dead-on. I think the TS2700 is an excellent tool and its whole point is clearly stated and very well executed. Reading your post, I realize I had misspoke in a previous message using the term 'dismayed'. The TS2700 gave me exactly what I was seeking, a spare PRS10. There was a time when I would have also appreciated the T1 input and output 1.544 MHz references. I think I rather surprised the local RBOC's engineer in our town of 40,000 when I ordered a T1 and 30 voice circuits for my bedroom back in 1994. As there was no internet service in that town when I moved there, I went about changing that. I regret intimating that the TS2700 is anything less that it purports to be. The reason for my posts about its internals is to see if it can do more that what it advertises. Things like a unused cutout in the case with the label GPS on the inside and a BTMon error message about PPS too high makes me wonder what the TS2700 can do beyond what's documented. I do wonder about its TOD capabilities. Yes, the time of day is clear in the BTmon. Thanks for the explanation of the term Craft. I see your point that some time of day information is coming though the RS-232 and Craft outputs. When I get the Rb back inside the TS2700, I look to see if any signals are coming out of the DE-9F connector labelled as TOD on the case. The PDF manual labels that connector as Not used. As the BTMon software has a TOD option where one can choose Cisco or NTP makes me think that there is a precision PPS signal somewhere on the circuit board. With the error message of Not implemented when one chooses Cisco or NTP, my suspicion is output on the TOD connector wasn't completed in firmware. But, perhaps a precision PPS will even be present on one of the TOD connector's 9 pins. I look forward to further investigation. Thanks again for your very informative post. Kevin ___ 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 TimeSource 2700
Kevin wrote: The reason for my posts about its internals is to see if it can do more that what it advertises. Things like a unused cutout in the case with the label GPS on the inside and a BTMon error message about PPS too high makes me wonder what the TS2700 can do beyond what's documented. The TS2500 was a very similar unit that received its timing signals from GPS. I assume they were built on the same case, hence the spare chassis hole (and perhaps also some features in BTMon that are not used by the TS2700). When I get the Rb back inside the TS2700, I look to see if any signals are coming out of the DE-9F connector labelled as TOD on the case. The PDF manual labels that connector as Not used. As the BTMon software has a TOD option where one can choose Cisco or NTP makes me think that there is a precision PPS signal somewhere on the circuit board. With the error message of Not implemented when one chooses Cisco or NTP, my suspicion is output on the TOD connector wasn't completed in firmware. But, perhaps a precision PPS will even be present on one of the TOD connector's 9 pins. I look forward to further investigation. Yes, please report your findings on the TOD connector. That connector, and the corresponding feature in the BTMon software, could apply only to versions of the TS2700 with an optional TOD function, or, more likely, to the TS2500 or other model built on the same chassis/motherboard. It will be interesting to see if there is any data there in a TS2700. Best regards, Charles ___ 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.
