Re: [time-nuts] Are these PRS10's worth it ?
In message 54a20c7c.7040...@skybase.net, Tim writes: Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) You need to hold that price up against the fact that a new PRS10 is $1600. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Are these PRS10's worth it ?
Hi I had two PRS10 units that failed after one year of use. It was not just the lamp, also the RF section that excites the lamp had problems. I think it is too expensive... Regards, Vasco Soares - Original Message - From: Tim t...@skybase.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tuesday, December 30, 2014 2:22 AM Subject: [time-nuts] Are these PRS10's worth it ? Hi all, Been on the lookout for a PRS10 to build a GPSDO+RB arrangement and I see these... http://www.ebay.com/itm/Stanford-Research-Systems-SRS-PRS10-Rubidium-Freq-Standard-12344101-08-no-lock-/231435472155 Is this just a reheat-the-bulb fix or do you suspect something more ? Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) thanks Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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] Are these PRS10's worth it ?
Check the difference between the LPRO and PRS-10 on John Miles' page: http://www.ke5fx.com/rb.htm Assuming these plots are representative of what you are likely to get from eBay parts (a pretty big assumption right there), the main advantage of the PRS-10 seems to be at high tau, where the performance of a GPSDRb is mostly driven by the GPS and PLL anyhow. Didier KO4BB On Tue, Dec 30, 2014 at 7:14 AM, Didier Juges shali...@gmail.com wrote: You can get a working LPRO for $150 with very reasonable shipping. To me, that's a better deal unless you absolutely need the thrill of trying to rescue something you knew was bad when you bought it :) http://www.ebay.com/itm/Datum-Efratom-Symmetricom-LPRO-10MHz-Rubidium-Oscillator-Tested-5-93-Lamp-Volts-/231436344277?pt=LH_DefaultDomain_0hash=item35e2ae5bd5 Didier KO4BB On Tue, Dec 30, 2014 at 3:15 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 54a20c7c.7040...@skybase.net, Tim writes: Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) You need to hold that price up against the fact that a new PRS10 is $1600. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Are these PRS10's worth it ?
My experience has been similar to Vasco's. Of three defective PRS-10s acquired for about $100 or less each, one had a bad MiniCircuits 400 MHz VCO module and was an easy fix. Another had a rubidium bulb issue that I traced to the driving FET. I managed to replace the FET, but the replacement's bias characteristics were somewhat different than its predecessor's, keeping the sensing circuits in an alarm mode. At the factory, bias adjustments are made in the software; but SRI does not provide access to this feature for customers. I tried removing and replacing the FET with still another, but messed-up the circuit board in the process. I wish now I had tried to alter the FET bias by adding external series or shunt resistors. The third unit has an intermittent condition that causes it to be slow to lock at times and fine at others. I have spent hours trying to trace this, but so far without success. If you decide to take a chance on these units, I would not be inclined to offer more than $100 as their repair is a crap-shoot. I suspect many of the units offered for sale on eBay have been removed from Symmetricom TS-2500 and TS-2700 telephone industry timing sources. PRS-10s from these seem to have Customer Number 123-44101-4 on the label. I have also encountered PRS-10s with the Customer Numbers 123-44101-08 and -10 on the label and assume these were from other Symmetricom instruments. By the way, The TS-2500 is a GPS-referenced source; however, the unit seems to compare its internal crystal oscillator with GPS, the PRS-10, and other 10 MHz sources (that can be connected for monitoring) and keeps track of their behaviors with a microprocessor. It appears the PRS-10 is not locked to GPS, but is simply monitored and kept in reserve as a replacement frequency and timing source should GPS service fail. If the PRS-10 frequency wanders out of the acceptable range, the TS-2500 shows a fault signal, but does not attempt to adjust the PRS-10. Apparently the PRS-10's frequency is set at the Symmetricom factory and the unit is on its own after that. It is included in the TS-2500 box as baggage to be used only if the GPS timing fails. As it is kind of expensive to burn an SRI PRS-10 simply as a standby, although this provision is understandably important to telephone companies, an unmodified TS-2500 is of questionable utility to hobbyists. Bruce, KG6OJI ___ 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] Are these PRS10's worth it ?
$219 for a bad RB seems to be silly. Sorry I am not that much of a gambler. Regards Paul WB8TSL On Tue, Dec 30, 2014 at 8:17 AM, Didier Juges shali...@gmail.com wrote: Check the difference between the LPRO and PRS-10 on John Miles' page: http://www.ke5fx.com/rb.htm Assuming these plots are representative of what you are likely to get from eBay parts (a pretty big assumption right there), the main advantage of the PRS-10 seems to be at high tau, where the performance of a GPSDRb is mostly driven by the GPS and PLL anyhow. Didier KO4BB On Tue, Dec 30, 2014 at 7:14 AM, Didier Juges shali...@gmail.com wrote: You can get a working LPRO for $150 with very reasonable shipping. To me, that's a better deal unless you absolutely need the thrill of trying to rescue something you knew was bad when you bought it :) http://www.ebay.com/itm/Datum-Efratom-Symmetricom-LPRO-10MHz-Rubidium-Oscillator-Tested-5-93-Lamp-Volts-/231436344277?pt=LH_DefaultDomain_0hash=item35e2ae5bd5 Didier KO4BB On Tue, Dec 30, 2014 at 3:15 AM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 54a20c7c.7040...@skybase.net, Tim writes: Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) You need to hold that price up against the fact that a new PRS10 is $1600. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Are these PRS10's worth it ?
Hi If indeed these PRS-10’s are out of TS boxes (and that’s a real good guess) there is one other thing to consider: Not all PRS-10’s are created equal. Some have fancy disciplining firmware in them. Some have better temperature specs. Some have better ADEV specs. Some (may) have longer running life specs. There also is a “good phase noise” version. When you look at PRS-10 plots, you need to ask “is this the version I have …”. For what ever reason, the ones out of the TS boxes are not the best of the bunch. I’d bet they simply put in the options they needed and cost reduced the other stuff out. The variation in PRS-10’s is not quite as crazy as on the FEI Rb’s. They all have the same basic outputs and at least respond to basic commands. Bob On Dec 30, 2014, at 1:00 PM, Bruce Hunter via time-nuts time-nuts@febo.com wrote: My experience has been similar to Vasco's. Of three defective PRS-10s acquired for about $100 or less each, one had a bad MiniCircuits 400 MHz VCO module and was an easy fix. Another had a rubidium bulb issue that I traced to the driving FET. I managed to replace the FET, but the replacement's bias characteristics were somewhat different than its predecessor's, keeping the sensing circuits in an alarm mode. At the factory, bias adjustments are made in the software; but SRI does not provide access to this feature for customers. I tried removing and replacing the FET with still another, but messed-up the circuit board in the process. I wish now I had tried to alter the FET bias by adding external series or shunt resistors. The third unit has an intermittent condition that causes it to be slow to lock at times and fine at others. I have spent hours trying to trace this, but so far without success. If you decide to take a chance on these units, I would not be inclined to offer more than $100 as their repair is a crap-shoot. I suspect many of the units offered for sale on eBay have been removed from Symmetricom TS-2500 and TS-2700 telephone industry timing sources. PRS-10s from these seem to have Customer Number 123-44101-4 on the label. I have also encountered PRS-10s with the Customer Numbers 123-44101-08 and -10 on the label and assume these were from other Symmetricom instruments. By the way, The TS-2500 is a GPS-referenced source; however, the unit seems to compare its internal crystal oscillator with GPS, the PRS-10, and other 10 MHz sources (that can be connected for monitoring) and keeps track of their behaviors with a microprocessor. It appears the PRS-10 is not locked to GPS, but is simply monitored and kept in reserve as a replacement frequency and timing source should GPS service fail. If the PRS-10 frequency wanders out of the acceptable range, the TS-2500 shows a fault signal, but does not attempt to adjust the PRS-10. Apparently the PRS-10's frequency is set at the Symmetricom factory and the unit is on its own after that. It is included in the TS-2500 box as baggage to be used only if the GPS timing fails. As it is kind of expensive to burn an SRI PRS-10 simply as a standby, although this provision is understandably important to telephone companies, an unmodified TS-2500 is of questionable utility to hobbyists. Bruce, KG6OJI ___ 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] Are these PRS10's worth it ?
Hi There is a lot of *stuff* in an Rb beyond just the lamp. It *could* be as simple as a VCXO centering adjustment. It also could be an alignment adjustment. I don’t believe there are any schematics out there on these devices, so it’s a “trace it out and see” sort of fix. Even with the schematic, if it’s an alignment (peak this / dip that / back off 1/8th turn) process there are no documents on any of the Rb’s for that stuff. If you want a science project, something like an FRK probably has easier access to the insides. There also are more people who have poked around in them. Personally I’d just wait for the next flood of $60 +/- $25 working parts to hit the market and stock up then. You are likely looking at getting two or three of the non-working parts to come up with one working one. That sort of money will buy a pretty good pile of the others. Bob On Dec 29, 2014, at 9:22 PM, Tim t...@skybase.net wrote: Hi all, Been on the lookout for a PRS10 to build a GPSDO+RB arrangement and I see these... http://www.ebay.com/itm/Stanford-Research-Systems-SRS-PRS10-Rubidium-Freq-Standard-12344101-08-no-lock-/231435472155 Is this just a reheat-the-bulb fix or do you suspect something more ? Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) thanks Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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] Are these PRS10's worth it ?
Bruce wrote: By the way, The TS-2500 is a GPS-referenced source; however, the unit seems to compare its internal crystal oscillator with GPS, the PRS-10, and other 10 MHz sources (that can be connected for monitoring) and keeps track of their behaviors with a microprocessor. It appears the PRS-10 is not locked to GPS, but is simply monitored and kept in reserve as a replacement frequency and timing source should GPS service fail. If the PRS-10 frequency wanders out of the acceptable range, the TS-2500 shows a fault signal, but does not attempt to adjust the PRS-10. Apparently the PRS-10's frequency is set at the Symmetricom factory and the unit is on its own after that. I have played with several TS-2700s (which are disciplined by CDMA cell transmitters rather than GPS), and they work the same way. They track all of the timing data they are given, and output the best fit 10MHz they can calculate using their BesTime engines. The TS-2700 keeps a running log of its estimate of the PRS10 frequency but, as you say, it does not adjust the PRS10. It is included in the TS-2500 box as baggage to be used only if the GPS timing fails. As it is kind of expensive to burn an SRI PRS-10 simply as a standby I'm not sure the TS-2700 (and, by implication, perhaps the 2500) ever just outputs the raw PRS10 frequency. I think it always outputs a frequency calculated from the various timing inputs. If it loses the CDMA signal and falls back to the PRS10, I think it uses the stored offset for the PRS10 to generate the output frequency. The manual says, If the CDMA signals are disrupted, the BesTime algorithm continues to predict CDMA timing information, which enhances system holdover performance. I don't know if it uses the last-known offset, or tries to project a current offset based on the trend line. 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] Are these PRS10's worth it ?
Hi all, Been on the lookout for a PRS10 to build a GPSDO+RB arrangement and I see these... http://www.ebay.com/itm/Stanford-Research-Systems-SRS-PRS10-Rubidium-Freq-Standard-12344101-08-no-lock-/231435472155 Is this just a reheat-the-bulb fix or do you suspect something more ? Not knowing much about the PRS10, I'm just wondering if its worth the ri$k :) thanks Tim -- VK2XAX :: QF56if23 :: BMARC :: WIA :: AMSATVK ___ 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.
