Re: [time-nuts] Nortel GPSDO osc age alarm
Hi Volker One possibility, as I found with one of these recently, is that your oscillator has aged such that the required EFC voltage for 10MHz output is now outside the range provided by the board. The EFC behaviour can be tracked if Lady Heather is enabled from switch on and the DAC voltage monitored. The EFC voltage should start at 3 volts, in my case reported by LH as 3.02 Volts, and will sit at this level until enough satellites are being tracked for the board to decide it can start the conditioning process, at which point the DAC voltage will ramp upwards over the course of a few seconds until the point is reached where the oscillator frequency crosses 10MHz and the control loop takes over. All standard stuff of course but, as you've discovered, if the oscillator hasn't reached 10MHz by the time the EFC voltage reaches, in my case anyway, approximately 5.6 volts the board's OSC report switches to BAD and Normal OSC age switches to OSC age alarm and LH highlights both in red. The EFC voltage finishes its ramp at 6 Volts, reported as 6.04 Volts, and then just sits there, all exactly as you're seeing. Having removed my faulty oscillator, something that needs to be done VERY carefully to avoid damage to the board, I found that it required an EFC voltage of just under 6.6 Volts for the the output frequency to reach 10MHz. The seller, fluke.l, was very helpful as always and offered to supply a replacement 34310-T oscillator, this one did have it's required EFC voltage in the correct range and resolved the problem. However, whilst waiting for the replacement to arrive I left the original oscillator on test and monitoring it for a while suggested that the only thing wrong with it was the required EFC voltage, so I reconnected it to the board using a wired lash-up on the bench with a simple 2 Volt level shifter inserted into the control loop and did indeed get a locked condition with Lady H reporting the DAC voltage from the board as close to 4.5 volts. This suggests that whilst the board design requires the oscillator EFC Voltage at 10 MHz to be between 3 and 6 Volts an oscillator that falls outside this range shouldn't automaticall be assumed to be faulty in more general terms, although it's obviously getting a bit long in the tooth and that doesn't help much if it happens to be soldered into your circuit board ! Whilst it is possible to remove and replace the original oscillator there is an alternative to physical replacement, one which I've now implemented, and this uses the mounting positions already available beneath the oscillator, not usable though until it's removed, to fit a couple of SMA or SMB connectors. These two connectors couple the 10MHz signal from the oscillator into the board (J9) and the EFC Voltage out to the oscillator (J10). Although there is a regulated supply available from the oscillator, which might be expected to supply the EFC circuitry, in practice this connection does not seem to be required. I have not investigated further as yet to determine whether the board auto senses and uses this supply if it is present, or whether it always just ignores it, but it doesn't seem to be an issue either way and it's interesting to note, at the extremes anyway, that LH does report the DAC voltage to be the same in both instances. The oscillator can be powered from the board or given its own supply, in which case the only required connections between them are the two coax leads. Using this arrangement, and some variation of a positive or negative level shifter if required, it becomes possible to use different oscillators with the Nortel board and it does become an even more interesting toy. One limitation though when using the Nortel boards in this way is that they don't seem to share the versatility of the Thunderbolt when it comes to modifying the oscillator conditioning parameters. It's suggested in the LH documentation that such commands are currently undocumented but that also leaves the possibility that any such change might only be a firmware option. If anyone has further information on this that would be much appreciated. I've been sufficiently impressed with the modified unit that I'm seriously considering modifying another one, even though it doesn't actually need it, although not over enthusiastic about repeating the oscillator removal. However, an added bonus with this configuration is that it's also more forgiving when it comes to any damage caused during removal of the original oscillator, since the pads for the external connectors are separate from the internal oscillator pads. Obviously it needs to be ensured that any necessary continuity is maintained but that could be easier if a board mounted oscillator is no longer required. The later single board unit, the NTBW50AA, has a similar external connector arrangement but in this case
Re: [time-nuts] Nortel GPSDO osc age alarm
Whilst on second thoughts it does seem a bit odd that this oscillator has passed 10MHz and still not locking this might be linked to the alarms being generated at around 5.6 volts as per my previous comment, even though the EFC voltage at the extreme does, theoretically at least, seem to be enough to implement the control function. I would still be very inclined with this unit to remove the oscillator and test it on its own. Regards Nigel GM8PZR In a message dated 23/01/2014 23:59:34 GMT Standard Time, ail...@t-online.de writes: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m 1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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] Nortel GPSDO osc age alarm
...thanks, Bob, it seems to be the oscillator, that is at it's limit, it cannot tune to 10 MHz at full EFC voltage, see new thread (started by Mark). Volker Am 24.01.2014 01:09, schrieb Bob Camp: Hi That’s a cell phone base station board. It’s got a bunch of outputs, some of which are related to the cell network it was built for rather than 10MHz. I’d bet your 9.8 MHz output is one of those. They are DDS based so there likely is some range of possible outputs. The age alarm is not unusual on a newly powered up board. It’s moving faster than it should. It may settle down. The DAC at limit is not a real good sign …. Bob On Jan 23, 2014, at 6:43 PM, Volker Esper ail...@t-online.de wrote: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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] Nortel GPSDO osc age alarm
Thanks so much, Nigel, for this very interesting mail. Yes, the voltages are exactly as my ones. And yes, I've removed the oscillator, already. I then removed the thermal isolation from the osc, as well as the label, in slight hope for a hidden tuning screw. Of course, there isn't any. I, too, had this idea to level shift the EFC voltage. So I took seat at my computer to find out, which maximum EFC voltage would be ok. And saw your mail. Do you have any further information about the osc? The number on the sign (Trimble *0110-2450-T* *34310-T*) isn't really informative. By the way: When removing the big Trimble label I found a smaller one beneath, reading DOC2127 0101/1940; I think it's a Tekelc osc? Is there a pull-up resistor behind the EFC input pin so that I could use two diodes for level shifting? Or how did you? This part is more thrilling than I expected... Regards Volker Am 24.01.2014 12:08, schrieb gandal...@aol.com: Hi Volker One possibility, as I found with one of these recently, is that your oscillator has aged such that the required EFC voltage for 10MHz output is now outside the range provided by the board. The EFC behaviour can be tracked if Lady Heather is enabled from switch on and the DAC voltage monitored. The EFC voltage should start at 3 volts, in my case reported by LH as 3.02 Volts, and will sit at this level until enough satellites are being tracked for the board to decide it can start the conditioning process, at which point the DAC voltage will ramp upwards over the course of a few seconds until the point is reached where the oscillator frequency crosses 10MHz and the control loop takes over. All standard stuff of course but, as you've discovered, if the oscillator hasn't reached 10MHz by the time the EFC voltage reaches, in my case anyway, approximately 5.6 volts the board's OSC report switches to BAD and Normal OSC age switches to OSC age alarm and LH highlights both in red. The EFC voltage finishes its ramp at 6 Volts, reported as 6.04 Volts, and then just sits there, all exactly as you're seeing. Having removed my faulty oscillator, something that needs to be done VERY carefully to avoid damage to the board, I found that it required an EFC voltage of just under 6.6 Volts for the the output frequency to reach 10MHz. The seller, fluke.l, was very helpful as always and offered to supply a replacement 34310-T oscillator, this one did have it's required EFC voltage in the correct range and resolved the problem. However, whilst waiting for the replacement to arrive I left the original oscillator on test and monitoring it for a while suggested that the only thing wrong with it was the required EFC voltage, so I reconnected it to the board using a wired lash-up on the bench with a simple 2 Volt level shifter inserted into the control loop and did indeed get a locked condition with Lady H reporting the DAC voltage from the board as close to 4.5 volts. This suggests that whilst the board design requires the oscillator EFC Voltage at 10 MHz to be between 3 and 6 Volts an oscillator that falls outside this range shouldn't automaticall be assumed to be faulty in more general terms, although it's obviously getting a bit long in the tooth and that doesn't help much if it happens to be soldered into your circuit board ! Whilst it is possible to remove and replace the original oscillator there is an alternative to physical replacement, one which I've now implemented, and this uses the mounting positions already available beneath the oscillator, not usable though until it's removed, to fit a couple of SMA or SMB connectors. These two connectors couple the 10MHz signal from the oscillator into the board (J9) and the EFC Voltage out to the oscillator (J10). Although there is a regulated supply available from the oscillator, which might be expected to supply the EFC circuitry, in practice this connection does not seem to be required. I have not investigated further as yet to determine whether the board auto senses and uses this supply if it is present, or whether it always just ignores it, but it doesn't seem to be an issue either way and it's interesting to note, at the extremes anyway, that LH does report the DAC voltage to be the same in both instances. The oscillator can be powered from the board or given its own supply, in which case the only required connections between them are the two coax leads. Using this arrangement, and some variation of a positive or negative level shifter if required, it becomes possible to use different oscillators with the Nortel board and it does become an even more interesting toy. One limitation though when using the Nortel boards in this way is that they don't seem to share the versatility of the Thunderbolt when it comes to modifying the oscillator
Re: [time-nuts] Nortel GPSDO osc age alarm
In a message dated 24/01/2014 17:06:43 GMT Standard Time, ail...@t-online.de writes: Thanks so much, Nigel, for this very interesting mail. Yes, the voltages are exactly as my ones. And yes, I've removed the oscillator, already. I then removed the thermal isolation from the osc, as well as the label, in slight hope for a hidden tuning screw. Of course, there isn't any. Nope, what you see is what you get, planned obsolescence wins again:-) I did find the thermal insulation to be quite useful in reducing the effects of drafts, as carefully observed by blowing on it:-), so well worth keeping in place once all is up and running again. I, too, had this idea to level shift the EFC voltage. So I took seat at my computer to find out, which maximum EFC voltage would be ok. And saw your mail. Do you have any further information about the osc? The number on the sign (Trimble *0110-2450-T* *34310-T*) isn't really informative. By the way: When removing the big Trimble label I found a smaller one beneath, reading DOC2127 0101/1940; I think it's a Tekelc osc? This is a comment from page 26 of the Nortel GPSTM General Spec available from Didier's site.. --- XXX will identify which OCXO was used in the particular device. XXX is to be either T, Oak, or T2. The T identifies the Tekelec Doc-1903 device and the Oak indicates the OFC-4895 device from Oak Frequency Control Group. A T2 will indicate the Tekelec Doc-2127 device. -which is interesting as it suggests your oscillator to be a T2 even though it's marked T. I'll have to take a closer look at mine:-) Is there a pull-up resistor behind the EFC input pin so that I could use two diodes for level shifting? Or how did you? I've got no information on the internal circuitry so I just assumed it would be a reasonably high impedance and used a single IC as a non-inverting unity gain summing amp powered from the onboard 12V supply for the oscillator to add, in my case, approximately 2V to the DAC output from the circuit board. I used a TL071, but only because that's what I had to hand, with 12K between the output and neg input and another 12k from the neg input to ground, then two 12k input resistors feeding into the pos input, one of which was connected to the EFC output from the board and the other biased very approximately to 2 Volts using a 4k7 and a 1K resistor as a divder across the 12V supply. Again no particular significance to the 12K, I just had some within easy reach. The output from the op amp was then used to feed the EFC voltage to the oscillator, and that was it. I hope that makes sense:-) In this instance I didn't make any attempt to further stabilise the supply to the op amp or the 2V reference but it was only intended to prove the point and I figured the control loop could take care of any small variations, and it actually worked quite well. Since then I've added the SMB connectors to the board and I'm running the replacement oscillator via a couple of pigtails and no offset for that one. Next step, assuming I ever get round to it:-), will be a proper enclosure with connections for an external oscillator, and perhaps even internal switching via a latching coax relay to allow internal or external options but will wait and see on that. Given the control limitations I mentioned earlier though I'm now considering perhaps leaving the other Nortel board as is and instead putting the effort into implementing a similar arrangement for a Thunderbolt, which of course has already been done by John Miles as referenced here http://www.ke5fx.com/tbolt.htm So, although I didn't feel over happy about having a faulty oscillator to start with, I'm actually very pleased with the way it turned out:-) Regards Nigel GM8PZR This part is more thrilling than I expected... Regards Volker Am 24.01.2014 12:08, schrieb gandal...@aol.com: Hi Volker One possibility, as I found with one of these recently, is that your oscillator has aged such that the required EFC voltage for 10MHz output is now outside the range provided by the board. The EFC behaviour can be tracked if Lady Heather is enabled from switch on and the DAC voltage monitored. The EFC voltage should start at 3 volts, in my case reported by LH as 3.02 Volts, and will sit at this level until enough satellites are being tracked for the board to decide it can start the conditioning process, at which point the DAC voltage will ramp upwards over the course of a few seconds until the point is reached where the oscillator frequency crosses 10MHz and the control loop takes over. All standard stuff of course but, as you've discovered, if the oscillator hasn't reached 10MHz by the time the EFC voltage reaches, in my case anyway, approximately 5.6 volts the board's OSC report switches to
Re: [time-nuts] Nortel GPSDO osc age alarm
Volker, I have also a Trimble Nortel NTG550AA and fortunately it works very well from the beginning. I have a downloaded manual and some other info that I can send you if interested. And one word of caution: if you observe the cable that goes from the main board to the small interface board, you will see that one of the connectors is reversed so be careful if you make a custom one for your cabinet, do it in the same fashion. Using a normal cable produces bizarre results that can actually drive you nuts, don't ask how I know. The coax connector, J5 is a 9.8304 MHz output, an odd frequency used by the cell tower equipment, J4 carries 1/2 PPS (even seconds), the next one (J1) is the for the antenna and J4 is the 10 MHz output. You already know that but I want to note that the 9.8304 frequency has mislead some users to think that it was the 10 MHz output, not your case. The seller (Bob Mokia , fluke.l) is well known to the Time Nuts, he has a technical background and normally known quite well what he sells and is very positive about solving the problems that may arise, his only problem is that his English is worse than mine . I think that he regularly monitors this list. I have observed a strange thing on this offering, at the end of the page he says: power on it ... after 30 minutes/it will locked/10mhz come on the SMB connector 1pps on the back d sub connector I never heard of a 1PPS signal on these units, only 1/2 PPS on the J4 coax and I had asked on this list if anybody had found how to extract 1 PPS from the unit. I have to put a scope on the DSR pin because it is the only connected to the main board other than TxD and RxD. Could you verify this on your unit when you change the OCXO and get it running? Best regards, Ignacio EB4APL On 24/01/2014 16:23, Volker Esper wrote: ...thanks, Bob, it seems to be the oscillator, that is at it's limit, it cannot tune to 10 MHz at full EFC voltage, see new thread (started by Mark). Volker Am 24.01.2014 01:09, schrieb Bob Camp: Hi That’s a cell phone base station board. It’s got a bunch of outputs, some of which are related to the cell network it was built for rather than 10MHz. I’d bet your 9.8 MHz output is one of those. They are DDS based so there likely is some range of possible outputs. The age alarm is not unusual on a newly powered up board. It’s moving faster than it should. It may settle down. The DAC at limit is not a real good sign …. Bob On Jan 23, 2014, at 6:43 PM, Volker Esper ail...@t-online.de wrote: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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. ___ 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] Nortel GPSDO osc age alarm
9.8304 MHz divided by 300 is 32,768 Hz. Feed that to an electronic clock and you will have an atomic clock of sorts. Regards Thomas Miller, Director of Wireless Services Skyline Network Engineering, LLC 443-250-6381 From: time-nuts-boun...@febo.com time-nuts-boun...@febo.com on behalf of EB4APL eb4...@cembreros.jazztel.es Sent: Friday, January 24, 2014 2:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Nortel GPSDO osc age alarm Volker, I have also a Trimble Nortel NTG550AA and fortunately it works very well from the beginning. I have a downloaded manual and some other info that I can send you if interested. And one word of caution: if you observe the cable that goes from the main board to the small interface board, you will see that one of the connectors is reversed so be careful if you make a custom one for your cabinet, do it in the same fashion. Using a normal cable produces bizarre results that can actually drive you nuts, don't ask how I know. The coax connector, J5 is a 9.8304 MHz output, an odd frequency used by the cell tower equipment, J4 carries 1/2 PPS (even seconds), the next one (J1) is the for the antenna and J4 is the 10 MHz output. You already know that but I want to note that the 9.8304 frequency has mislead some users to think that it was the 10 MHz output, not your case. The seller (Bob Mokia , fluke.l) is well known to the Time Nuts, he has a technical background and normally known quite well what he sells and is very positive about solving the problems that may arise, his only problem is that his English is worse than mine . I think that he regularly monitors this list. I have observed a strange thing on this offering, at the end of the page he says: power on it ... after 30 minutes/it will locked/10mhz come on the SMB connector 1pps on the back d sub connector I never heard of a 1PPS signal on these units, only 1/2 PPS on the J4 coax and I had asked on this list if anybody had found how to extract 1 PPS from the unit. I have to put a scope on the DSR pin because it is the only connected to the main board other than TxD and RxD. Could you verify this on your unit when you change the OCXO and get it running? Best regards, Ignacio EB4APL On 24/01/2014 16:23, Volker Esper wrote: ...thanks, Bob, it seems to be the oscillator, that is at it's limit, it cannot tune to 10 MHz at full EFC voltage, see new thread (started by Mark). Volker Am 24.01.2014 01:09, schrieb Bob Camp: Hi That’s a cell phone base station board. It’s got a bunch of outputs, some of which are related to the cell network it was built for rather than 10MHz. I’d bet your 9.8 MHz output is one of those. They are DDS based so there likely is some range of possible outputs. The age alarm is not unusual on a newly powered up board. It’s moving faster than it should. It may settle down. The DAC at limit is not a real good sign …. Bob On Jan 23, 2014, at 6:43 PM, Volker Esper ail...@t-online.de wrote: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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. ___ 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. CONFIDENTIALITY NOTICE: The information contained in this electronic message is confidential information intended for the use of the individual or entity named above. If the reader of this message is not the intended recipient, or an employee or agent responsible for delivering this electronic message to the intended recipient, you are hereby notified that any dissemination or copying of this communication is strictly prohibited. If this message
Re: [time-nuts] Nortel GPSDO osc age alarm
Ignacio, thanks for your message. Answeres within the text: And one word of caution: if you observe the cable that goes from the main board to the small interface board, you will see that one of the connectors is reversed so be careful if you make a custom one for your cabinet, do it in the same fashion. Yes, I've seen that by chance, when disconnecting the board to reassemble the oscillator. Using a normal cable produces bizarre results that can actually drive you nuts, don't ask how I know. It's a wonder you didn't kill the beast... ...the 9.8304 frequency has mislead some users to think that it was the 10 MHz output, not your case. Me, too, at the beginning The seller (Bob Mokia , fluke.l) is well known to the Time Nuts Yeah, of course, I know. The thing is, usually people are cautious naming sellers. Time Nuts' point of view isn't quite that narrow. Ok, yes, I admit, it's Bob ;-) 1pps on the back d sub connector I read that, too, but like you I only found the even PPS. I have to put a scope on the DSR pin because it is the only connected to the main board other than TxD and RxD. Could you verify this on your unit when you change the OCXO and get it running? That's no problem, the GPS stuff works well on my item. I'll post a message. Regards Volker ___ 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] Nortel GPSDO osc age alarm
Nice! I didn't know that. But what a number, 300... Why such a digital-hostile factor? Why not 256 or 512? Volker Am 24.01.2014 20:51, schrieb tmil...@skylinenet.net: 9.8304 MHz divided by 300 is 32,768 Hz. Feed that to an electronic clock and you will have an atomic clock of sorts. Regards Thomas Miller, Director of Wireless Services Skyline Network Engineering, LLC 443-250-6381 From: time-nuts-boun...@febo.com time-nuts-boun...@febo.com on behalf of EB4APL eb4...@cembreros.jazztel.es Sent: Friday, January 24, 2014 2:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Nortel GPSDO osc age alarm Volker, I have also a Trimble Nortel NTG550AA and fortunately it works very well from the beginning. I have a downloaded manual and some other info that I can send you if interested. And one word of caution: if you observe the cable that goes from the main board to the small interface board, you will see that one of the connectors is reversed so be careful if you make a custom one for your cabinet, do it in the same fashion. Using a normal cable produces bizarre results that can actually drive you nuts, don't ask how I know. The coax connector, J5 is a 9.8304 MHz output, an odd frequency used by the cell tower equipment, J4 carries 1/2 PPS (even seconds), the next one (J1) is the for the antenna and J4 is the 10 MHz output. You already know that but I want to note that the 9.8304 frequency has mislead some users to think that it was the 10 MHz output, not your case. The seller (Bob Mokia , fluke.l) is well known to the Time Nuts, he has a technical background and normally known quite well what he sells and is very positive about solving the problems that may arise, his only problem is that his English is worse than mine . I think that he regularly monitors this list. I have observed a strange thing on this offering, at the end of the page he says: power on it ... after 30 minutes/it will locked/10mhz come on the SMB connector 1pps on the back d sub connector I never heard of a 1PPS signal on these units, only 1/2 PPS on the J4 coax and I had asked on this list if anybody had found how to extract 1 PPS from the unit. I have to put a scope on the DSR pin because it is the only connected to the main board other than TxD and RxD. Could you verify this on your unit when you change the OCXO and get it running? Best regards, Ignacio EB4APL On 24/01/2014 16:23, Volker Esper wrote: ...thanks, Bob, it seems to be the oscillator, that is at it's limit, it cannot tune to 10 MHz at full EFC voltage, see new thread (started by Mark). Volker Am 24.01.2014 01:09, schrieb Bob Camp: Hi That’s a cell phone base station board. It’s got a bunch of outputs, some of which are related to the cell network it was built for rather than 10MHz. I’d bet your 9.8 MHz output is one of those. They are DDS based so there likely is some range of possible outputs. The age alarm is not unusual on a newly powered up board. It’s moving faster than it should. It may settle down. The DAC at limit is not a real good sign …. Bob On Jan 23, 2014, at 6:43 PM, Volker Esper ail...@t-online.de wrote: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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. ___ 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. CONFIDENTIALITY NOTICE: The information contained in this electronic message is confidential information intended for the use of the individual or entity named above. If the reader of this message is not the intended recipient
Re: [time-nuts] Nortel GPSDO osc age alarm
On 1/24/14 11:57 AM, Volker Esper wrote: Nice! I didn't know that. But what a number, 300... Why such a digital-hostile factor? Why not 256 or 512? Volker Am 24.01.2014 20:51, schrieb tmil...@skylinenet.net: 9.8304 MHz divided by 300 is 32,768 Hz. Feed that to an electronic clock and you will have an atomic clock of sorts. Regards 9.8304 is 300 baud * 32768. So you can generate all the conventional digital data rates (1200,2400,.., 38.4k with powers of two). Typically, a UART wants to see a clock that is 16x or 8x bit time, so you need something a bit higher. ___ 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] Nortel GPSDO osc age alarm
Oukaay - I should've known... Thanks, Jim! Am 24.01.2014 21:12, schrieb Jim Lux: On 1/24/14 11:57 AM, Volker Esper wrote: Nice! I didn't know that. But what a number, 300... Why such a digital-hostile factor? Why not 256 or 512? Volker Am 24.01.2014 20:51, schrieb tmil...@skylinenet.net: 9.8304 MHz divided by 300 is 32,768 Hz. Feed that to an electronic clock and you will have an atomic clock of sorts. Regards 9.8304 is 300 baud * 32768. So you can generate all the conventional digital data rates (1200,2400,.., 38.4k with powers of two). Typically, a UART wants to see a clock that is 16x or 8x bit time, so you need something a bit higher. ___ 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] Nortel GPSDO osc age alarm
In a message dated 24/01/2014 21:48:27 GMT Standard Time, ail...@t-online.de writes: New ways of RF design - see photo ;-) - Definitely the last word in high rise developments:-) And glad to hear you got it sorted. Ok, I put three 1N4148 in series between DAC out and EFC in and a pull up of 4k7 up to 12V. It shifts the DAC voltage 1.8 volts up, so the osc is able to tune to 10MHz+3Hz. Locked! Now I can go back to the sofa, having a beer or two, being sweet again to my wife and my dog, :-) Thanks Volker Am 24.01.2014 17:49, schrieb Volker Esper: Thanks so much, Nigel, for this very interesting mail. Yes, the voltages are exactly as my ones. And yes, I've removed the oscillator, already. I then removed the thermal isolation from the osc, as well as the label, in slight hope for a hidden tuning screw. Of course, there isn't any. I, too, had this idea to level shift the EFC voltage. So I took seat at my computer to find out, which maximum EFC voltage would be ok. And saw your mail. Do you have any further information about the osc? The number on the sign (Trimble *0110-2450-T* *34310-T*) isn't really informative. By the way: When removing the big Trimble label I found a smaller one beneath, reading DOC2127 0101/1940; I think it's a Tekelc osc? Is there a pull-up resistor behind the EFC input pin so that I could use two diodes for level shifting? Or how did you? This part is more thrilling than I expected... Regards Volker Am 24.01.2014 12:08, schrieb gandal...@aol.com: Hi Volker One possibility, as I found with one of these recently, is that your oscillator has aged such that the required EFC voltage for 10MHz output is now outside the range provided by the board. The EFC behaviour can be tracked if Lady Heather is enabled from switch on and the DAC voltage monitored. The EFC voltage should start at 3 volts, in my case reported by LH as 3.02 Volts, and will sit at this level until enough satellites are being tracked for the board to decide it can start the conditioning process, at which point the DAC voltage will ramp upwards over the course of a few seconds until the point is reached where the oscillator frequency crosses 10MHz and the control loop takes over. All standard stuff of course but, as you've discovered, if the oscillator hasn't reached 10MHz by the time the EFC voltage reaches, in my case anyway, approximately 5.6 volts the board's OSC report switches to BAD and Normal OSC age switches to OSC age alarm and LH highlights both in red. The EFC voltage finishes its ramp at 6 Volts, reported as 6.04 Volts, and then just sits there, all exactly as you're seeing. Having removed my faulty oscillator, something that needs to be done VERY carefully to avoid damage to the board, I found that it required an EFC voltage of just under 6.6 Volts for the the output frequency to reach 10MHz. The seller, fluke.l, was very helpful as always and offered to supply a replacement 34310-T oscillator, this one did have it's required EFC voltage in the correct range and resolved the problem. However, whilst waiting for the replacement to arrive I left the original oscillator on test and monitoring it for a while suggested that the only thing wrong with it was the required EFC voltage, so I reconnected it to the board using a wired lash-up on the bench with a simple 2 Volt level shifter inserted into the control loop and did indeed get a locked condition with Lady H reporting the DAC voltage from the board as close to 4.5 volts. This suggests that whilst the board design requires the oscillator EFC Voltage at 10 MHz to be between 3 and 6 Volts an oscillator that falls outside this range shouldn't automaticall be assumed to be faulty in more general terms, although it's obviously getting a bit long in the tooth and that doesn't help much if it happens to be soldered into your circuit board ! Whilst it is possible to remove and replace the original oscillator there is an alternative to physical replacement, one which I've now implemented, and this uses the mounting positions already available beneath the oscillator, not usable though until it's removed, to fit a couple of SMA or SMB connectors. These two connectors couple the 10MHz signal from the oscillator into the board (J9) and the EFC Voltage out to the oscillator (J10). Although there is a regulated supply available from the oscillator, which might be expected to supply the EFC circuitry, in practice this connection does not seem to be required. I have not investigated further as yet to determine whether the board auto senses and uses this supply if it is present, or whether it always just ignores it, but it doesn't seem to be an issue
Re: [time-nuts] Nortel GPSDO osc age alarm
9.8304 MHz output, an odd frequency used by the cell tower equipment 9.8304 MHz is 8 x 1.2288 MHz which is the CDMA PN chip rate a rather fundamental frequency to the CDMA phone system Zim ___ 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] Nortel GPSDO osc age alarm
Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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] Nortel GPSDO osc age alarm
Hi That’s a cell phone base station board. It’s got a bunch of outputs, some of which are related to the cell network it was built for rather than 10MHz. I’d bet your 9.8 MHz output is one of those. They are DDS based so there likely is some range of possible outputs. The age alarm is not unusual on a newly powered up board. It’s moving faster than it should. It may settle down. The DAC at limit is not a real good sign …. Bob On Jan 23, 2014, at 6:43 PM, Volker Esper ail...@t-online.de wrote: Hi! I bought a Trimble/Nortel GPSDO http://www.ebay.de/itm/300933951405?ssPageName=STRK:MEWNX:IT_trksid=p3984.m1497.l2648 and Lady Heather's now tells me that everything is alright - except - DAC 6.04V - OSC BAD - osc age alarm The rectangle 10MHz output signal (J5) shows a signal at about 9.8MHz (a deviation of about 200kHz), wobbling 4Hz up and down. Oddly enough, the direct oscillator output (J4) shows a sine wave at a stable 10.004MHz (a deviation of 0.4Hz). It seems to me it's not the oscillator that is bad but the servo loop - what can I do? Thank you Volker ___ 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] Nortel GPSDO osc age alarm
The OSC age alarm says the oscillator EFC control voltage is getting near to its programmed limit. The DAC alarm says that the EFC dac setting is it is at the limit. I suspect that your oscillator EFC input is bad. I've seen this on a couple of boards. ___ 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.
