[time-nuts] Lucent GPS "RFTGm-II-Rb"
Wonder if anyone on the list has information about a Lucent Rubidium locked to GPS unit I have? Its relatively new, maybe five years old. Purportedly to be from a failed cell site venture that caused the unit to be sold surplus having never been installed. The nomenclature on it is: Lucent: KS-24019 L109 which I assume may be an in house part number or contract number. The model number is: RFTGm-II-Rb . I've posted some pictures at: http://campus.pari.edu/gps-freq/Lucent560F.JPG http://campus.pari.edu/gps-freq/Lucent561F.JPG http://campus.pari.edu/gps-freq/Lucent562F.JPG The unit comes up and locks an OCXO to GPS. Then after some more warm up time it switches over to the locked Rubidium side and the OCXO switches to become the standby. My problem with it is that when I come back the next day the Rb side has faulted out and pushed the system back onto the OCXO as the main online 10 MHz source. Its unlikely the Rubidium lamp is old enough to be a problem, or that the initial frequency adjustment has drifted out of range.. though I suppose its remotely possible. Have been running the unit on 24vdc but would try more if I thought the normal -48 ~ 56vdc telco battery strings were used with this. It gets warm enough on 24vdc that I didn't want to chance it until I asked. I know if its a switcher that it might actually run cooler on higher voltage due to a proportionate drop in current. Just haven't had a chance to reverse engineer it all. I see RS422 labeling on some of the ports. But without more info I'm proceeding with caution and somewhat at a standstill as to what's going on. Anyone have any experience with these units? Thanks, Charles S. Osborne, K4CSO Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Unknown Efratom 10MHz Assy, information asked
Richard, and Arnold, Very timely comments. I may be in the middle of working on one of those Lucent units. Or maybe mine is a slightly different version. The front panel on my unit says RFTGm-II-Rb (for the Efratom LPRO Rubidium locked side) and RFTGm-II-XO on the GPS locked OCXO side. I placed the unit's pictures at: http://campus.pari.edu/k4cso/gps/Lucent/Lucent560F.JPG http://campus.pari.edu/k4cso/gps/Lucent/Lucent561F.JPG http://campus.pari.edu/k4cso/gps/Lucent/Lucent562F.JPG Mine has a string of failures in the 24vdc lines feeding both the Rb and OCXO sides. Tracked down a blown 3A fuse just prior to two tantalums causing high current. Removing them powered up a 28vdc to 5vdc DCDC converter but didn't bring everything back alive. On the OCXO board the same 3A 24vdc line fuse was blown and diode prior to it. The OCXO so far isn't getting any DC on its pins. Haven't tracked down the source of its power yet, but suspect its related to the other problems. Probably all related to lightning damage that also took out the GPS receiver in my Z3801A. The Lucent unit did work, but not fully, at one time as the pictures show. But after it warmed up the Rb side would fail back over to the OCXO side. Does anyone have a pinout for the RS422/1PPS or Interface dB15 connectors on this type unit? And is there any software out there which will look into the lock status/control similar to GPSCon does with the Z3801A/Z3816As? Thanks, Charles S. Osborne, K4CSO Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] - Original Message - From: "Richard H McCorkle" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" Sent: Monday, October 31, 2005 4:56 PM Subject: Re: [time-nuts] Unknown Efratom 10MHz Assy, information asked > The board you are describing is used in the Lucent RFG-M-XO reference > frequency generator. It takes in 10 MHz on J2 from a Rubidium oscillator and > disciplines the Efratom SC cut OCXO on the main board from the 10 MHz input. > The output from the OCXO is converted to 15 MHz and supplied as the > reference output on J4. > The RFG-M-RB and RFG-M-XO normally mount together in a chassis (which I didn > 't get) and the modules are connected to the chassis by a harness with a > DB15 on the chassis end. The pin out for the harness is as follows: > > DB15M TO/Pin# Description > Pin # > 1RFG0 - P1-1+24v 1.3A/0.6A > 2RFG0 - P1-2Common > 3RFG1 - P1-1+24v 0.6A/0.4A > 4RFG1 - P1-2Common > 10 RFG0 - J3-1 Alarm > 11 RFG0 - J3-2 Alarm > 12 RFG1 - J3-1 Alarm > 13 RFG1 - J3-2 Alarm > > A second interface cable ties the RB to the XO as follows: > > RBJ5 XOJ5 > Pin #Pin# > 15 > 33 > > The male DB9 is P1 and pin 1 = +24v @ 400ma, Pin 2 = Common. This will power > up the board so you can verify operation of the OCXO. Unfortunately that is > all the information I have on the unit. > Hope this helps. > > - Original Message - > From: "Arnold Tibus" <[EMAIL PROTECTED]> > To: "Discussion of precise time and frequency measurement" > > Sent: Monday, October 31, 2005 10:02 AM > Subject: [time-nuts] Unknown Efratom 10MHz Assy, information asked > > > > Hello to the group, > > I have got in my hands a very nice looking board > > from EFRATOM equipped with a 10 MHz OCXO. > > The designation on the top of the board is > > 55761ASSY104920-001 > > the label underneath shows > > 55761-104919-001 > > The Ocxo P/N is 105243-001, 10,00MHz > > The board is complete with 3 x 9pin D-Type connectors > > 2x fem. 1x male, which seem to be the connector > > for the powering of the assy. > > There are 2x SMA conns. fem., J2 and J3, J1 is not > > assembled. > > > > For memory backup there is a mignon battery holder on. > > The small board monted on top of the main board > > does have a PLL system with a 74HC4046N and a lot > > of other typical chips assembled (CD4060, 74HC08, > > 54HC573F, AD75388Q and others.). > > I guess this was a part of a Rb-reference device, > > too nice to disassemble. > > > > Therefore I ask into the round table all the experts, if there > > is somebody who could help me with more details, circuit diagram > > or I/F informations etc. > > > > As I am anyway trying to set up a GPS disciplining system > > for a 10 MHz OCX
[time-nuts] GPS receiver replacements for UT+
I'm looking for replacement GPS receiver daughter boards for the Z3816A or Z3801A or CNS Clock. Have been to Synergy's website and asked their support group where to find Motorola UT+ form/fit/function compatible units, but they kept pointing me at the newer smaller Motorola FS. If this has come up before, I must have missed it. Frequent lightning storms in summer keeps me in the hunt for these boards. Even with lightning protection on the coaxes the EMP still gets a few every year. Thanks, Charles S. Osborne Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] GPS receiver replacements for UT+
Reradiating the GPS antenna signal for isolation is an interesting idea. I had not considered it. I had a Trimble Scout handheld GPS that used that method to couple in a magnet mounted car rooftop GPS antenna signal into the built in antenna inside the handheld. It used a little clip on reradiating adapter. Wish the Trimble Scout was still alive. It had an excellent well thought out feature set in software. It's display gradually quit working and Trimble considered it obsolete and unreparable when I asked six or seven years ago. I saw one of those units in a GPS historical display in the Smithsonian museum in Washington. That's when you know your technology is becoming dated. Hi! Thanks, Charles S. Osborne Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] - Original Message - From: "Bjorn Gabrielsson" <[EMAIL PROTECTED]> To: "Charles S. Osborne" <[EMAIL PROTECTED]> Cc: "Discussion of precise time and frequency measurement" Sent: Thursday, January 05, 2006 8:53 AM Subject: Re: [time-nuts] GPS receiver replacements for UT+ > "Charles S. Osborne" <[EMAIL PROTECTED]> writes: > > > If this has come up before, I must have missed it. Frequent lightning storms > > in summer keeps me in the hunt for these boards. Even with lightning > > protection on the coaxes the EMP still gets a few every year. > > Ever tried a reradiating antenna to further separate the GPS from the > dangerous outside? Does such a solution have any technical drawbacks > wrt timing accuracy? > > It might not be cheaper than to buy a new lowcost oem receiver board, > but if you want to protect hard to replace units it could be a > solution. > > I have only used the "professional" type of kits like found here, > > http://www.navtechgps.com/supply/rerad.asp > > I know there is also a lower end market for use inside cars and the > like, > > http://www.prairie.mb.ca/tri_m.htm > > > -- > > Björn > ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] PC clock comparison software?
I have a query. Does anyone have a favorite network time sync test software? Here's my situation. Being at a radio and optical observatory, most everything we do has varying degrees of time stamp criticality on the stored data. While I could get obsessive compulsive and try to get everything sync'd every few seconds with the Z3816A/GPSCon server, much of the data is quite usable at 100ms or less time accuracy. I'd like better of course. But for the moment let's just say I need to evaluate where we are, and improve from that. Most PCs sync to our time server frequently. But PC clocks being the cheap crap that they are, I need to have some reasonable way of measuring how quickly they drift. ... particularly if Windows is experiencing Attention Deficit Syndrome and forgetting to run the core applications while they obsessively go speak to Father Bill Gates for words of wisdom or check in with the Mother Ship or whatever it is that they seem to need an Internet connection to do. For test purposes I've occassionally set the time server polling routine to once a day and seen 20 minute errors on delinquent PCs. Other PCs might stay within a minute. If I try to run the Net-time routine every minute then I increase the chance that the time server will be busy and not respond. A goodly handful of these PCs are chugging along quite happily running small applications on Pentium-166s /Win98se with limited memory. So going to XP or Linux is not an option in half the PCs. No time, No $$. All the normal educational, not for profit, zero budget reasons. Is there a small application that could log the time errors when the system clock gets set? This would help me decide how often the time needs to update and what my time error penalty would be if I can't run it that often. I know temperature will even enter into it as well since several PCs are in unheated buildings. It also would be nice if it could log when the time server does not respond. Some applications respond very ingratiously when the time server won't answer their query. They hang the program or never resync with the network even when it comes back. But I can't prove that this is happening. Naturally our IT folks say the network is running flawlessly. But I'm not that gulible. One other idea is to have a central PC poll the outlying PCs for their time and compare to network time. That reverse net-time sync approach would be even more useful since the PCs are spread all over many buildings, some a km of fiber away, and checking/downloading/evaluating their individual logs would be a chore in itself. Our network is about 30 PCs on fiber OC12 ( 622Mbps) ATM with 100mbps ethernet network branches. In the near future some video conferencing and remote telescope users will add to the chunkiness of the network variable load. Thoughts on my test software delemma? Thanks, 73, Charles S. Osborne, K4CSO Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] PC clock comparison software?
Lots of good info as always from this list. I probably should mention what some of these PCs are doing. Someone asked about the telescope control PCs. The 26m dishes have their own dedicated GPS receivers for their local time standards. Those do the celestial navigation and tracking via their control PCs. Our optical telescope control PCs are almost all on XP or Win2000. So NTP should have them covered reasonably well. Test software would confirm how well. The PCs that tend to misbehave the most are Win98se Pentium 100 ~ 400 MHz. They are doing a variety of menial tasks like: seismic data, solar flare monitoring, meteor burst recording, VLF signal recording for Sudden Ionospheric Disturbances, and cosmic ray montoring. They churn along at 4 ~ 40 samples per second typically of constant data flow to the hard drive. Every minute or so they may push a screen capture to our website. Others with a somewhat higher workload are doing webcam or weather station image pushes to our website once a minute. For time/frequency we have two Z3816As and a Ball Efratom MRT free running Rubidium frequency standard. I tweak it using an HP53131time interval counter compared to the Z3816A. GPSCon V1.038 is the software running on a Win98se box. I have a newer XP box I've been trying to move to for better serving reasons. But it keeps turning itself off every night even though we've tried to turn off power saving and automatic updates. Its on a UPS with four 100AH batteries, plus four 7AH gel cells on float on the Z3816A 48vdc power side. The slightest power glitch still takes the XP computer down even though its on the UPS. But the Win98se P166 plugged into the same outlet strip on the same UPS weathers it all for months at a time without rebooting. The main network servers are Linux of one variety or another. Not sure what the latest flavors are, but mostly Red Hat Linux Fedora Core I think. The network glitches are probably power glitch related even though most things are on UPSs. We're pretty far up in the mountains, so lightning and AC supply side glitches are common. And the sheer size of the facility induces surges from EMP transferred cable to cable on site too. The primary fiber links are via 3Com ATM Core Builders with redundant fiber links. Its mostly once things get out to the localized 8~24 port switches that latch up occurs I think. Diagnostic code would help troubleshoot that since I could see which branches failed when, and if they recover. Network loading is minimal except from the main website server to the Internet via T1 ( soon OC3, then that will be minimally loaded too except during distance learning and video conferencing). tnx, Charles S. Osborne, K4CSO Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] LUCENT RFTG-m-RB
I'll try to get the pinout off mine when I get home and post it. Charles S. Osborne Technical Director Pisgah Astronomical Research Institute 1 PARI Drive, HC 73, Box 638 Rosman, NC 28772-9614 http://www.pari.edu 828-862-5813 direct 828-862-5554 main 828-862-5877 FAX [EMAIL PROTECTED] - Original Message - From: "Norman J McSweyn" <[EMAIL PROTECTED]> To: "Discussion of precise time and frequency measurement" Sent: Friday, December 22, 2006 7:09 PM Subject: Re: [time-nuts] LUCENT RFTG-m-RB > Did anyone get the pinout for the "p1 24v" on the rfg-rb?? > Mine has an LPRO. > Norm n3ykf > > > ___ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Wanted to buy or borrow -- RFTG-m-XO L106A
John, I have my RFTGm-II-XO (L109) open on the workbench (I'm changing the 15MHz output to 10 MHz) and tried the sequence you mentioned below. Mine reacts similarly. However, if you reapply a 10 MHz external source to the "10 MHz REF In" sma it locks after maybe 15 minutes and XO frequency stabilizes. Initially the Fault lite is on, then clears, and a minute later the "No GPS" which was on solid, clears. Note, if you are using the original 15 MHz output frequency, there is muting applied when things are not stabilized and fault LED is lit. My RFTGm-II-Rb (L108) unit isn't working. Haven't had time to continue troubleshooting it since I moved and changed jobs last year, and am just getting my home lab back in working shape. The Rb unit draws excess current and blows an on board fuse. I found a few shorted tantalum chip caps two years ago when I had it opened up. But apparently that's not all of the problems. It took collateral damage after a lightning hit took out most GPS connected receivers like my Z3801A in spite of a surge suppressor. I was sort of waiting for someone on time-nuts, to answer the question of whether the Rb is disciplined or just used to extend the holdover time. Seems like I remember it going thru a sequence where the Rb switched over and acted as primary for a few hours during initial power up. And once the GPS-XO stabilized it became the ONLINE unit and the Rb went to STANDBY. But its been almost five years since all that was working, so my memory of that sequence could be wrong. It would make sense if the GPS-XO was primary and the Rb acted during holdover wouldn't it? Wish someone had a manual (or the RS422 magic decoder software). I've sort of been patiently waiting and watching for someone on time-nuts to uncover a copy of the Lucent cellsite documentation or something to explain the LED bahavior on these units. It's more than just ON and OFF indicators, since they flash as a third status indication format also. 73, Charles S.Osborne, K4CSO Duluth, GA - Original Message - From: "John Ackermann N8UR" <[EMAIL PROTECTED]> To: "Tom Van Baak" <[EMAIL PROTECTED]>; "Discussion of precise time and frequency measurement" Sent: Saturday, March 15, 2008 3:21 PM Subject: Re: [time-nuts] Wanted to buy or borrow -- RFTG-m-XO L106A > I'm not sure what's going on. I ran my XO/RB pair for 30 days, using > the "official" interconnect cable with the monitoring software > indicating no problems. I took phase data from the RB output via the > TSC and fed it into Stable32 (by the way, with a 20 second timeout, the > 30 day TSC data capture worked fine). > > The results show a reasonably constant +1.5 microsecond slope over 30 > days, about 6x10e-13 offset. There's no characteristic cliff in the > ADEV where the GPS kicks in, but yet the offset is better than I would > expect from the LPRO running in standalone mode. Plots are at > http://www.febo.com/pages/oscillators/rftg/ > > I then pulled power on the RB unit and instead of going into proper XO > operation, I got "NO GPS" and "FAULT" on the XO. In separate > experiments, pulling the interface cable or the 10 MHz cable result in > the same faults -- the XO doesn't seem to take over as it should. > > And, when I measure the XO output, it is just horrible -- ADEV in the 9s > from 0.1 second out past 10,000 seconds. > > I wonder -- has ANYONE gotten the -XO module to work in GPS-disciplined > mode??? > > John > > Tom Van Baak said the following on 03/15/2008 03:25 PM: > >> I suspect the XO module in my RFTG setup is defective, so I'd like to > >> find another one. It needs to be the "L106A" (not "B") version to mate > >> with my -RB (L105A) unit. > >> > >> Anyone have one they'd like to sell? Or, failing that, one I could > >> borrow to test in my system? > > > > John, > > > > Interesting, my RFTG pair won't lock right either; I'm thinking > > my XO module has a problem too. Do you think we're making > > the same mistake or are both of our XO modules faulty? > > > > /tvb > > > > > > ___ > > 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] Racal-Dana 1992 switches
Matt, Not seeing a better alternative posted for the Racal 1992, and having dozens of similar bad Toko switches on some Pacific Measurements 1038-N10 Scalar Analyzers, I decided to buy a bunch of the Jameco ones and give it a try. Definitely not a form fit replacement. But if you're not too asthetically picky they do fit. The leads can be manually flattened with a pair of needle nose pliers and reformed to fit under and down to match the closer hole spacing. Also clip off the small plastic alignment pins to allow the switches to sit flush on the board. The process only takes a couple of seconds per switch. A lot quicker than removal of the original switches. The real catch is the hole size in the 1992 original switch layout is a couple of sizes smaller on one pin than the other. Using a #54 drill bit (no bigger) you can clean the hole out and enlarge it without taking the plated thru barrel out of the holes on that one side. All my switches are in and working. I didn't even put the keycaps back on as all the manual lead forming didn't necessarily center within the original panel cutouts and the plastic posts are adequate for use as switches. The numerical keys in center keypad may require Dan's epoxy trick. Haven't gotten to that yet. Now the real question is... is there a clever way to make the Racal 1992 readout the difference in µHz between two GPS disciplined oscillators? My only other counter, an HP5384A, is offscale at 10.000 000.000 MHz . I'm referencing the counter with one Lucent RFTG-m-XO and clocking a Lucent RFTGm-II-XO. Things are working well enough to be beyond my counter's ability to see any jitter. The Racal says nanosecond time interval counter, so I bet there's a way to subtract and increase the resolution similar to an HP53131? tnx, Charles K4CSO Duluth, GA - Original Message - From: "Matt Ettus" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "Discussion of precise time and frequency measurement" Sent: Monday, March 24, 2008 1:46 PM Subject: Re: [time-nuts] Racal-Dana 1992 switches > On Mon, Mar 10, 2008 at 8:47 AM, Dan Rae <[EMAIL PROTECTED]> wrote: > > David McGaw wrote: > > > > >Does anyone know of a source of push-button switches for the > > >Racal-Dana 1992? I have one that over half are bad. No luck from > > >Racal-Dana or their service house. > > > > > > > > The original makers of that switch (Omron?) stopped making them years > > ago. I wonder why? > > > > The last time I did this I found a switch at Jameco that was a near > > exact replacement. The only difference was that the button was a little > > too loose a fit and needed a dab of epoxy inside to hold it firmly in > > place. These have been working in mine now for at least five years. > > The type I used was KIE22 (29 cents each in 100s), however the ones I > > got then with a cross section shape blue plunger do not look exactly > > the same as the ones pictured in the current on line catalog. Some > > further research is indicated obviously... > > > > Once they start to go they will all need to be replaced, I'm afraid. > > > > I bought the ones in the catalog, but they don't fit. The footprint > is bigger, for one thing. > > Matt > > ___ > 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] Racal-Dana 1992 switches
Bill, I guess my reason for wanting to see beyond 0.001 Hz is the usual, I have reached a limit and wonder if the equipment I have is capable of more, if I just understood the more esoteric functions I seldom use. The Racal seems like my scientific calculator.. lots of shift functions that might be hiding some useful capabilities with a little coaching and study. Just saw Pete's answer, and I do have a PTS160 synthesizer. So the locked offset idea is do'able. Have mixers, phase detectors, but may need more info on the zero crossing detector opamp portion if you could point me in the right direction. >From a GPS equipment standpoint more resolution might tell me if my GPS receivers are working good enough or marginally. I passive split the antenna line four ways. The Lucent units lock to it with about 34~45 C/N readings. But my Z3801A has some other issue now that I've replaced the UT+. It hasn't locked and gives recurring "UTC receiver timeout" messages on GPScon. The previous UT+ receiver was somewhat lightning damaged and would only lock to one or two satellites for a few hours a day, but at least it was communicating. It may just be a comm issue between the Z3801A motherboard and my present UT+, since the Z3801A motherboard does answer back with serial number etc to GPScon. So I know the baud rate at that level is communicating between PC and Z3801A. The UT+ is a used one from one of the Lucent RFTGm units. So maybe there's a difference in the way they were setup. The UT+'s are 2000 vintage Synergy R5122U1112 to Lucent with V2.2 firmware and no battery. I actually have collected enough damaged UT+ boards (from the lightning prone place I previously worked) that I should build up an NMEA test fixture to verify they work outside the systems they normally reside in, and that all the parameters are set correctly. Then I can try to resurrect a few. The M1501 LNA chips are usually what goes. And I have some ideas I want to try, to dead bug in a MMIC fix for that obsoleted LNA chip. Charles Osborne K4CSO, EM74wa Duluth, GA - Original Message - From: "Bill Hawkins" <[EMAIL PROTECTED]> To: "'Discussion of precise time and frequency measurement'" Sent: Friday, March 28, 2008 9:09 PM Subject: Re: [time-nuts] Racal-Dana 1992 switches Charles S. Osborne said, in part, "Now the real question is... is there a clever way to make the Racal 1992 readout the difference in µHz between two GPS disciplined oscillators? My only other counter, an HP5384A, is offscale at 10.000 000.000 MHz . I'm referencing the counter with one Lucent RFTG-m-XO and clocking a Lucent RFTGm-II-XO. Things are working well enough to be beyond my counter's ability to see any jitter. The Racal says nanosecond time interval counter, so I bet there's a way to subtract and increase the resolution similar to an HP53131?" Haven't seen the answer on this list, so perhaps it occurred privately. The Racal 1992 is able to read the phase error between two 10 MHz signals (A and B) in degrees. I have done this with the outputs of two 3801s, which are the only pair of frequency sources that I have. This would be sub-nanosecond accuracy except that the display shows 3-10 degrees of jitter (difference between two successive readings). This, however, is only 10E-9. Most people on this list are investigating areas at least two orders of magnitude lower. I find that the phase method gives me comparative drift errors soon enough. An hour gets you near 10E-12. Others require measurement intervals much shorter than that, but the phase angle method is more than adequate for time errors that humans will notice. A drift of one second per year is on the order of 10E-8. It all depends on your reason for pursuing accurate time/frequency measurement. Bill Hawkins ___ 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] Lucent RFTG-m-XO 15MHz -> 10MHz
I've done three 15 MHz to 10 MHz conversions now, an RFTGm-II-Rb, RFTG-m-XO, and an RFTGm-II-XO. So I'll mention the quick and dirty mod that worked. The circuit boards are virtually identical between all three. I pulled the 15 MHz metal cased filter out. Backtrack from the +23dBm 15 MHz output, thru the buffer amplifier, and you'll run into the metal bandpass filter. I used an oscilloscope to find the 10 MHz output on the OCXO. Using a 470pf ceramic monolithic capacitor I ac coupled off a sample of the RF via a small coaxial cable. Then route it over to a resistive power divider into the missing filter's output socket. The resistive divider is a very small 1K ohm 10turn pot in series with the coax center conductor. I used a 51 ohm from the filter output to ground to form the other part of the divider and help terminate the buffer amp input. This allows all the level alarm circuitry or whatever is under the daughter board to continue functioning. The potentiometer is adjusted to drive the output buffer amp to +23 dBm at 10 MHz output just like it was with 15 MHz originally. I also have the original 15 MHz passive external distribution divider for the system. So the +23 dbm drives the splitter to give six 10 MHz outputs at +9 dBm each. It's an interesting divider. I'll have to take it apart sometime. It has two inputs to allow the Rubidium RFTGm-II-Rb unit's output to become the backup source. When the XO output fails it's muted, and the Rb takes over as online source. By the way I modified the RFTGm-II-Rb the same way to use the buffer amp to output 10 MHz from the LPRO. The associated boards are identical between the Rb and the XO, just stuffed with different parts. In fact there's a spot for the GPS receiver, its just missing parts. Maybe when I learn a lot more about the loop constants and how they interact I'll get ambitious and try grafting the LPRO into the XO system to see if that results in a GPS locked Rb. My RFTGm-II-Rb however still has problems. Thanks to the help of several on the time-nuts list, I did get both units functioning redundantly again after the lightning damage several years ago. But after about six or eight hours the Rb side turns itself off. I'm thinking a DC-DC converter is probably overheating inside and shutting down. Over the next month I hope to open it up and confirm that. I may just use an external power supply and remove the suspect 5v dc-dc converter as a test of the theory. Always hard to test a thermal problem when the only way to do it is to open the box confining the heat. 73, Charles Osborne, K4CSO - Original Message - From: "Bo Granlund" <[EMAIL PROTECTED]> To: Sent: Sunday, April 13, 2008 4:08 PM Subject: [time-nuts] Lucent RFTG-m-XO 15MHz -> 10MHz > Hi everybody, > > Sorry for asking this kind of stupid question, but I've tried to do my best > with google and it hasn't revealed a lot of decisive results. > > The thing is, I have a Lucent RFTG-m-XO that outputs 1PPS and 15MHz signal. > I was wondering, how do you go ahead and convert the 15MHz output to a > 10MHz output? What kind of equipment do I need in between there to make > this happen? > > I'm really sorry, because I do realize this is a really stupid question, but > I'm kindof out of ideas, and I'm more of a software guy than an electronics > guy. :) > > Oh, there is a 10MHz input to the RFTG-m-XO. What is the purpose of this > input? > > kind regards, > Bo Granlund > > ___ > 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] Efratom LPRO Rubidium
I have one of the Lucent RFTGm-II-Rb Rubidium cell site standards. It's misbehaving. Knowing the amount of experience on this list, I figured I'd ask before I dive in much deeper where I have no schematics. Initially I believed one of the DC-DC converters was not working after warmup. But after remoting the voltages to test points, they seem to be OK. The system did suffer a lightning strike some years ago, which took out the UT+ GPS receiver in the RFTGm-II-XO. But that's working after the UT+ was replaced. And I doubt the interconnected circuits would have been affected. Power supply for instance was floated across 24VDC of gell cell batteries, which usually can absorb a lightning spike pretty well. The unit powers up about +200 Hz above 10 MHz (mine is modified to no longer put out 15 MHz). After 30 minutes it has dropped slowly to +150 Hz. It briefly shows an online indication then. But a few minutes later that goes off and the fault light comes on. The frequency drops as low as +129 Hz as things continue to heat up. A couple of days later its still in the +129 ~+149 Hz range. I can heat and cool it and move the frequency ( +157 Hz at 90°F inside the Lucent box, +129Hz at 110°F), so the loop definitely isn't in control. I also have its companion RFTGm-II-XO connected to it with the factory wiring harness. The XO is GPS locked and working fine exceeding my ability to read its error accurately but sub-milliHz. Counter is clocked by Z3801A 10 MHz as reference. Lucent diagnostic monitor software says "unit failed", "oscillator maintenance required". My question then, is there anything one can access that might be adjusted to bring the OCXO back within capture range? +140 Hz seems way beyond where it should be. I thought the OCXO tuning range on something like this was normally +/- a few Hz. The unit is circa 1999 vintage. Low mileage, probably has two years online time to date (so likley not an Rb lamp problem). When I bought it, it was new in the box and still in warranty, victim of a cell site buildup deal gone bust and surplused out. At one time the two units would back each other up, switching from one to the other once as they warmed up. Anything user servicable in the LPRO? I assume a trip to the real service center would cost as much as a good used car. So if its something I can't correct, it'll become a dissection learning experience. One final test I haven't run, is removing the LPRO and powering it up stand alone, just in case the C field input is the problem. I assume it should be capable of locking with those inputs floating if the LPRO is indeed OK? Anyone know what: BITE (Built in Test?), Xtal Mon, Lamp volt, and C-Field should be normally? Thanks, Charles Osborne, K4CSO Duluth, GA ___ 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.
