[time-nuts] Casio Wave Ceptor wrist watch - quick accuracy test
Hi! There seems to be some kind of comeback going on with 80's style digital watches. You may find replicas of some 80's models or even re-makes of the original models from original manufacturer. So I decided to get one. As a time-nut my primary goal was to have radio controlled 'atomic' model. So I ended up to Casio Wave Ceptor WV-59DE-1AVEF. There's many models available from basic digital models like this to very nice ones with with full titanium body (analog style). But because of the 80's is hot it had to be digital... Wave Ceptors suport all time signals formats (US, UK/German and Japan) and correct standard is automatically selected when home city is set. One of the first things to do was to test the accuracy with radio syncronization turned off. Correct time was fist set with DCF77. Then I switched off the synconization. After beign about three days off there was no significiant visible error on time. In the video we can see however about one frame error, which means about 40 milliseconds. Still that's pretty good result for wrist watch. Also, the syncronization will occur once per day when the reception is good. So the watch must be at least calibrated in the factory. Don't know if the watch performs any kind of self-calibration according to radio syncronization results, most likely not - but it would be technically possible. So far so good, it's accurate enough - at least as new. When syncronization is turned on, there should never be visible error on time. Here's my test video: https://www.youtube.com/watch?v=_A23buFeHd0 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TS2100 OCXO Conversion: Command exploration
Philip Jackson kirjoitti: It's been a while since I last played with a TS2100 given the roll over issue, but IIRC the "lock" LED is an indication that you have more than a specified number of satellites (four sounds familiar) with a signal reading above a certain threshold. I don't think it means oscillator discipline lock. No, TRACKING indicator is for that and LOCK indicator means that PPS is within 1 microsecond of UTC. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TS2100 OCXO Conversion: Command exploration
Hi! I have TS2100 which I modified from TCXO to OCXO. I have the 'offical' MTI OCXO, which I bought from someone on this board. I have also replaced the GPS unit to the HEOL Design model, which was required to get correct time at all. It's also much more accurate than the original Trimble. Now, with all this said: I'm still waiting for a 'Lock' indicator on the front. It's tracking, and the D/A value certainly has changed from what I had it at last night, but I'm still not getting a lock. Here are my current numbers: If I turn off the unit and the OCXO is totally cooled down then it might need even 2-3 hours before getting the LOCK indicator on again! So please be patient. According to my measurements the LOCK indicator will turn on when the PPS has gone within 1 microsecond of UTC. But it's not fully locked even at this point! With HEOL Design GPS unit it will end up within 50 nanoseconds of UTC, but that requires even more time. If you have trouble with locking you should compare the PPS with oscilloscope with some other receiver (for example Thunderbolt) or maybe you could 'steal' the PPS from the internal GPS and compare it with output. You should see it trying to reach the correct PPS and if it passes it at startup, it should change the direction and finally settle near the PPS input. In case of trouble you could also try with different A/D values manually and see what they do. root timing utils tfp 0 -- returned 0x00f2 That cannot be correct: Value is too low, near zero volts perhaps and it might be clipped. Looks like it has drived itself to the lower limit without getting correct feedback. This is a clear sign that clock steering is not working at all. From my unit: 1 ? tim 2 ? utils 3 ? tfp 0 0xb676 root timing utils tfp 6 -- returned KM = 0.9994965 4 ? tfp 6 KM = 0.9994965 root timing utils tfp 7 -- returned KO = 0.9994965 5 ? tfp 7 KO = 0.9994965 root timing utils gain -- returned gain now:20 (There seems to be a 6 ? gain gain now:-20 root eng eeprom info -- returned 0024 Same here. Please note that to enable any eeprom writes you must close JP4 temporary. By the way: you don't need to start every command with 'root'. It just resets the menu structure back start every time, which sounds impractical. You gan enter the menus, type '?' to see the available commands and go back to previous menu level with 'pop' command. Any thoughts on why I don't have a lock as yet? According to A/D value it looks like clock steering is not working at all. You should use oscilloscope to find out if A/D values have any effect at all. If you have rubidium or other kind of 10 MHz source put it to one trace of oscilloscope and TS2100 10 MHz output to another. Then try with different A/D values manually and see if it's even possible to get waves syncronized. If it's not possible with any A/D value then it will never lock, perhaps your OCXO is not compatible. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Lady Heather 5 leap second video
Hi! Trimble thunderbolt and direct on-screen capture with 1 fps from Lady Heather 5 running on Windows XP. 23:59:59 --> 00:00:60 --> 00:00:00 https://youtu.be/pJt8bHAo_yU It doesn't do it beautifully anymore, like older version did: https://youtu.be/DbvMZikqtI4 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 1PPS users?
Hi Bob, One thing I've never really understood is who actually uses the high-quality 1PPS output from a GPSDO. I use it for NTP server, like many others also do around the world. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Google public NTP service
Michael Rothwell kirjoitti: ... was just announced. https://cloudplatform.googleblog.com/2016/11/making-every-leap-second-count-with-our-new-public-NTP-servers.html?m=1 I wonder what this stupid "leap smear" will do to NTP driftfiles. Only Google may be stupid enough to grow one second lasting minor timing issue to ten hours lasting serious timing issue with even longer effects if driftfiles will be adjusted to neet their temporary and changing non-standard clock rate. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 53132A Display
Bert Kehren via time-nuts kirjoitti: Did buy a HP53132a counter mainly to use with the RS 232 for high resolution and to have a backup for my very favorite 5345a with 40 GHz head. Sadly the very clean unit has a very weak display to the extend that an 8 looks like a 9. Have the option for a full refund but would like to explore alternatives. Any ideas. Some VCR's with VFD displays had this same issue in 80-90's. It was usually dead (dried) electrolytic capacitor somewhere in VFD drive circuits, causing poor drive voltage levels. After replacing the dead capacitor the display was as new. Regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Spectrum Analyzer Specifications
time...@metachaos.net kirjoitti: I have another question about test equipment. When using a spectrum analyzer to examine the output of a frequency standard, what are the minimum specification needed? Bandwidth, resolution, sensitivity, etc? It depends what you want to measure from there. In general, analysis of this kind of strong signals are not very difficult but if you want to find weak spuriouses there then the dynamic range of the SA may become a problem. Looking at spectrum analyzers on eBay, I see quite a bit of difference between various models. Some have a resolution of 10Hz but others are 30Hz or even 100Hz. This usually means resolution bandwith (RBW) and it has nothingh to do with actual frequency resolution. RBW means the bandwith of the adjustable IF filter in the SA signal path. With low bandwith you can see signals which are very close to each other but the sweeping will be slow. With high bandwith you can sweep large frequency areas in milliseconds but any sinals closer than RBW will be shown as one signal peak only. That's why it's very important to select correct RBW depending of what we are measuring. Usually the RBW selection is done auotmatically based on frequency span setting. What comes to actual frequency resoltion you can usually set the center frequency with few decimals, it's not very accurate and it even doesn't have to be. When you sweep, you can analyze the peaks found in the trace with marker, but this is not accurate unless your spectrum analyzer is equipped with frequency counter function. With counter function you can select the peak to be analyzed with marker and then use marker count function to see the actual frequency with that peak with the resolution of the counter (can be 1 Hz or 0.1 Hz for example -not as precise as with universal couner). But the difference with universal counter here is that you can count very faint signals also (for example less than -100 dBm) and you can select the signal to be counted even when there's multiple signals mixed. You may have some strong signal where your universal counter locks but then there's some faint signal mixed with it. If you want to count this faint signal you can do this with spectrum analyzer's counter easily. With the counter function you will also need option to feed external 10 MHz reference to the SA. Without external ref the counter is mostly useless because it may have serious frequency error. This error is also stongly dependent of the frequnecy what you count. For example if you want to count something around 10 GHz, only 1 Hz error in the 10 MHz refernce means 1000 Hz error in the counted value at 10 GHz. Some have a minimum frequency of 0.01Hz, 100Hz or even in the kHz range. Some are only sensitive to 60dBm, but others over 100dBm. It's -60dBm or -100dBm. Both are quite poor values for spectrum analyzer but may be adequate if you only analyze strongs signals like oscillators. Are any of the cheaper USB spectrum analyzers worth getting? If you want to analyze only "easy" signals like oscillators etc. then yes. For anything more precise or very faint signals, I'd say no. Most of these are appallingly expensive, so knowing what is needed can certainly help guide a purchase or to minimize cost. And if a "deal" is found, knowing that it is or is not adequate can help. Yes, good specrum analyzers usually costs more than 2000 USD even as used. Also, a "high end" used 2000 USD specrtum analyzer can be much better than brand new "entry level" 1 USD specrum analyer. And if you need any kind of vectored signal analysis, demodulation capability of modern communications etc. then the price will be very high. Hope this helps... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Next step up from basic GPS/PPS timekeeping
What would be my next step up be, hardware-wise, in terms of improving precision, stability, etc? A GPSDO? Budget is limited as far as these things go - about £150 UK/$210 US. I have Symmetricom TS2100 with OCXO and GPS upgrades as primary server, accessible only at local network. It has about +-50 ns nominal PPS accuracy. Then there's another server based on Raspberry Pi2, which is accessible from Internet. The PPS from symmetricom is fed to Rpi2 and the actual time and date information is passed from TS2100 to Rpi2 with NTP. Rpi2 can serve about 1 NTP queries per second, according my stress tests with ntpload.c test program by Kasper Pedersen. For stress test, several PC's are needed, each running few threads of ntpload.c, all bombarding the server under test simultaneously. Rpi2 has quad core processor, but unfortunately it looks that ntpd can utilize only one core. With about 1 ntp queries per second there's only one core with 100% load and others are basicly idling. Good thing is that you can run another tasks simlataneously, without noticeable slowdown. I also joined the NTP pool (only Finnish one) but then I noticed that it's was really bad idea to run any NTP server behind router/firewall. When there's rush peaks in NTP pool, there will be several hundreds (I had more than 600) NTP queries per second and each from different address of course. This will create a lot of sessions in router NAT table, in my case there was more than 13000 active sessions according to conntrack -C. This may overwhelm the router and in any case it will eat lot of RAM on the router. The lesson learnt was that NTP server should have it's own direct WAN access without any router. That might also decrease the delays. This will be my next setup. The Rpi2 NTP server itself seems to be very stable and there was no issues when I did the stress test with continuous ~1 queries/sec for about one day. Regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time sync from cellphone TO microcomputer
Jim Lux kirjoitti: While this is trivial with a GPS receiver, we were thinking about a very minimalist implementation, with a smart phone as the control interface. Forget the smart phone - at least if it's un-rooted Android. I'm not sure how the default time sync is done, it's either by Google servers (which are famous of their non-standard way to handle leap seconds) or NITZ protocol from cellular network. Either way the time quality is very poor. It may be off even tens of seconds and usually it's off at least couple of seconds at most of the time. You can have it synced by millisecond only by rooting it first and then installing some kind of NTP client or application. But it will be in sync only as long you keep the display on. I believe there's some kind of power saving methods wich cause the clock to go off-sync right after the display is turned off. This can be seen with NTP application easily. So I prefer to use Raspberry Pi for example. You can create even Startum 1 level NTP server with GPS receiver and Rpi. It works with same USB power supply than most smart phones and it can have WiFi if you want. Regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Datum TS2100 10MHz frequency drift
Philip Zahariev via time-nuts kirjoitti: Unfortunately I'm not happy with results because 10 MHz output signal after GPS lock (both leds on front "Locked" and "tracking" are "ON") has frequency drift (phase shift) with period around one second plus minus ~18 deg (+-5 ns) compared to other 10 MHz. I measure this by 2 channel scope on 10 nS sweep, first channel connected to TS2100 10 Yes it works like that and it seems to update the DAC value once per second. Frequency wobbling is perfectly in sync with PPS output, which is kind of logical. If you look TS2100 manual it says "stand alone time server" which means it's designed to serve as time standard - not as frequency standard. If you need stable frequency then you should try with Rubidium oscillator or with some other GPS unit. For example Thunderbolt has much more stable frequency output than TS2100, but it's also a timing receiver, not frequency standard. However with OCXO and GPS upgrades you will get more than 10 times better timing than original TS2100. Without upgrades the TS2100 PPS is just below 1 microsecond, with MTI OCXO and Heol Design N024 GPS board it's about +-50 ns. So it's relatively good for every day timing purposes.. :) Of course you could try could be to play with timing constant settings but I don't think it would help anything if the DAC is still written once per second. But if you find better values please let us know! Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] UPS for my time rack
Chris Waldrup kirjoitti: I have decided I'd like to get a UPS to put on the rack containing my Thunderbolt, the laptop that runs Lady Heather, and frequency counter. Has anyone had bad experience noise wise with the APC brand units like are available on Amazon and at Staples? I'd like to get one that doesn't generate lots of RFI. Thank you. Get a line-interactive model which has inverter with classic iron transformer. Line-interactive means that the inverter is not continuously on when the mains voltage is OK, but the mais voltage is routed thru multitap transformer which gives some filtering and enables to fix under/overvoltage errors without turning on the inverter. When there's blackout and inverter is really started the transformer will act as a filter which reduces the HF interference caused by sine wave inverter. You can recognize this kind of ups from treir weight. For example 2 kVA model should weight more than 25 kg without batteries and more than 50 kg with batteries. You could look for example old APC SmartUPSes or APC Matrix UPS, which has separate inverter unit, transformer unit and battery units. Old SmartUPS'es may require float voltage modification because their charging voltage tends to increase when aging. Without fix it will kill the batteries too soon. Worst case to buy is double conversion on-line model without any kind of transformer. These are cheap but the inverter is on all the time and it's output is not filtered. I have measured the output of these kind of UPSes with spectrum analyzer and they are really horrible interference sources. Not recommended if there's any kind of sensitive electronics. Regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] SRS FS710 spurs at 50Hz and harmonics?
Anders Wallin kirjoitti: I seem to get very strong spurs at 50Hz and harmonics with an old second-hand SRS FS710: http://www.anderswallin.net/2015/09/srs-fs710-noise-measurement/ feature or bug? Anyone looked at the powersupply and figured out what parts to change? If you live in a country with 50 Hz mains network then this sounds like a dead capacitor in the power supply. Usually this means that it has old fashioned linear power supply (with classic iron transformer). In that case, replace the secondary capacitors after the rectifier bridge(s). Check voltages with oscilloscope if you wanna see which ones, but it might be good idea to replace them all (there should't be many of them). Should be very easy to fix. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] LAN/USB to GP-IB/HP-IP Adapters
Brooke Clarke kirjoitti: motherboard is not longer made so I'm looking for an adapter that runs from LAN or a USB port. > NI has the GPIB-USB-HS+ (their latest version) so the prior version GPIB-USB-HS is available for under $200. Can anyone comment on what's available? I have this: http://prologix.biz/gpib-ethernet-controller.html There's also USB version available, but personally I perfer ethernet because it's so much better when instruments are accessed from multiple computers. It's always connected on the network so it's always ready when needed, without plugging anything etc. Never used it with LabView but according to websites it should be supported. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] UPDATE: Heol N024 GPS for TS-2100 Failure
Gerhard Wittreich kirjoitti: Heol is sending me and another timenut a new GPS board with the updated firmware. If you have an early version of the board, be on the lookout for loss of Tracking as a symptom of the problem. If this is a same issue that I discovered, it seemed to happen at each Saturday evening (UTC). But there's no need to reboot anything, it will recover by itself, just sit back and wait... Loss of tracking event stays maybe about an hour or something and then it will return to normal. So it's only a minor problem, unless you need full PPS accuracy (+-50 ns with OCXO). If TS2100 is used as FTP server, this temporary loss of tracking doesn't matter. Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom® TS2100-GPS update and conversion
Gregory Beat kirjoitti: I removed the Trimble ACE III receiver (39818-C), but noted that this specific unit had a widget board (65398.69) on the SMA antenna connector and 2 wires (DC power) to the 3-pin header on the main board. Was this board used to support +12 VDC powered outdoor antennas? It's antenna biasing circuit, includes 5V regulator to create bias for antenna. It's not needed with Heol N024 anymore, N024 feeds the needed bias itself. Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] [Bulk] Leap second results: LH screenshot
J. L. Trantham kirjoitti: Interestingly, the time is 23:59:60 but the UTC ofs is still 16. I guess it increments to 17 at the end of that operation, i.e., at 00:00:00. That is exactly how it should be. See my video of 2012 leap sec: https://www.youtube.com/watch?v=DbvMZikqtI4 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Lady Heather leap second display
VK2DAP kirjoitti: I am hosting a small party and don't want to look like a dill more than I already do. Just make sure that UTC time is selected in thunderbolt settings. Check my Lady Heather video from 2012, if there's any help for the settings: https://www.youtube.com/watch?v=DbvMZikqtI4 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TymServe 2100 and the 1995 GPS issue
Gerhard Wittreich kirjoitti: Once locked I did notice something interesting but maybe not important. The control voltage to the oscillator (timing util tfp 0) went from a very consistent 0xba6f to a 0xbb02. That's about 0.2% of scale. I'll watch it over the next few days to see where it settles in. Sounds like oscillator aging to me, sometimes they do larger jumps, stay there for a while and then again... Also it would not be suprising that this would happen just after the power was off and oven was cooled down for a moment. Also, brand new oscillators seem to age more rapidly at start and then settles down when older but the effects of aging will never stop completely. But they seem to get better and better when aging. I'm also waiting my MTI OCXO to arrive... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TymServe 2100 1995 Issue - A Kludgy Fix
descoubes kirjoitti: I am very pleased to inform you that the 1995 year bug on the TS2100 has been solved. You will have to replace the existing Trimble ACE III GPS receiver by our N024 with special firmware. Does this also correct the 1 sec offset caused by upcoming leap second? To remind, TS2100 GPS mode failed already in February, having 1 sec offset right after the information about upcoming leap second was added. How can we know that it doesn't fail again when actual GPS week rollover will happen? Now it seems to be week 1846 and 2047 will come less than four years. Did you test this with GPS simulator? Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IRIG-B audio decoder circuits and ICs sought
Joseph Gwinn kirjoitti: When I last used IRIG-B005, the vendor (Symmetricom?) said it was good for a few meters only on shielded twisted pair. I recall that the handling of shield grounds was strange. This was OK, because the signal was confined to one cabinet, and it worked just fine. But there was no mention that the B005 followed RS422 or RS485 or anything else. Nor does IRIG 200-04 say this, so I suspect that each company solves it differently. Yes, there seems to be many implementations. Quote from Technical Note TN-102 from Cyber Sciences: http://www.cyber-sciences.com/documents/TN-102_IRIG-B.pdf The IRIG 200-04 standard does not define specific signal levels for IRIG-B. Typical techniques for transmission of unmodulated IRIG-B include: - TTL-level signal over coaxial cable or shielded twisted-pair cable - Multi-point distribution using 24 Vdc for signal and control power - RS-485 differential signal over shielded twisted-pair cable - RS-232 signal over shielded cable (short distances only) - Optical fiber Typical techniques for transmission of modulated IRIG-B include: - Coaxial cable, terminated in 50 ohms or higher. - Shielded twisted-pair cable So your main concern with unmodulated version is compatibility between different vendors. Yes, planning to buy at least one spare unit when their prices will drop on Ebay... :) The problem is that they don't handle GPS week field overflow gracefuly. Yes. Internal GPS of TS2100 cannot be used anymore, it failed alrady in February. Used external PPS since then. Since having external PPS is major problem for most of the TS2100 users I hope that the price of these units will drop soon on Ebay. I'm interested to buy especially rubidium version of the TS2100, if someone has working one having only the GPS problem... Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TymServe 2100 1995 Issue - A Kludgy Fix
descoubes kirjoitti: I am working for HEOL DESIGN company, and we are currently investigating this TS2100 1995 bug. We have developped the N024, a clone of Trimble ACE III receiver (which is mounted inside the TS2100). They are many issues with the TS2100-ACE III internal protocol, and we have good hopes to solve it out by N024 software. Thanks for the information. Of course it would be nice to get the internal GPS working too. I was planning that rude solution could be to cut off the GPS serial port lines and use only it's PPS output so that TS2100 sees it as external PPS. This would require changes to TS2100 motherboard (PPS should be routed so that it's feeded to Ext_PPS input). That hack would throw away anything else than PPS but will keep the unit in time as long there's no interruption on GPS reception. Of course this means that the time, leap second data etc. must be set manually (like now) but the worst thing is that there would be no way to see any GPS status anymore. If it loses signal, there will be absolutely no indication. Another solution could be like this, but with added microcontoller. Also in this solution only the PPS is routed to TS2100 directly. GPS serial port would be routed to microcontroller instead. Microcontroller would handle the GPS time decoding and follow TS2100's time from IRIG-B signal. If it notices that TS2100 time is gone wrong, it could correct the time and leap second settingc etc. by using TS2100 console serial port. If TS2100 follows PPS correctly, this should only happen in the startup. This would bring back the automatic time setting but this requires very much work. Also in this solution the main trouble is the loss of GPS status. To fix this, iw could be possible to share the TS2100 LCD display so that also TS2100 LCD port is routed thru the microcontroller, which could alter the LCD data from TS2100 before sending it to LCD. In the main display the 2nd line of LCD shows always Datum Tymserve 2100, which is kind of useless information. So the microcontroller could filter that away and write the GPS status there. TS2100 LCD looks like standard HD44780 and it would not impossible to capture the data, alter it and send to display. Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IRIG-B audio decoder circuits and ICs sought
Joseph Gwinn kirjoitti: I prefer the DC level shifted variant of IRIG-B. I like and use IRIG-B00x too, but it only reaches a few meters, versus the required tens of meters. It's differential RS485-alike bus (with TS2100 at least) using 5V signalling level. It works easily more than few meters with twisted pair cable. For RS485 they claim more than kilometer if the speed is less than 100 kbit/s and here it's only 100 bit/s. So only tens of meters there's no problem. I think the AM was originally intended for transmitting IRIG-B wirelessly or analog tape/film soundtrack recoring... Yes, but I must have IRIG-B12x (Amplitude modulated 1 KHz sine wave), and the analog processing complicates things. I think that one best implements the IRIG decoder in a DSP chip. Yes and there will be delays. As long decoding delay remains constant, it's easy to compensate. In my implementation the decoding delay is 48 cycles (9,6 usec) and remains constant. Actually this is delay from rising edge verification to timer setting point. When decoding IRIG-B it's one second behind. Timekeeping functions are needed anyway. Data verification system comes as a side product. It's only needed to compare last received IRIG-B frame with timestamp of passed second. If times differ then there's bit errors OR timekeeping is out of sync. Code has to decide when it should just ignore the received data and when it should syncronize the internal timekeeping. TS2100s are generating a lot of replacement business for GPS vendors. Yes, planning to buy at least one spare unit when their prices will drop on Ebay... :) To be modern, one must code in C? Isn't that true? I use assembler only with these 8-bit PIC's. It's little bit special case, there's no point to use assembler with any larger processors. This little baby has only 35 assembly commands. Because most of them run in single cycle it's quite easy to write time critical code like this IRIG-B decoder. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] IRIG-B audio decoder circuits and ICs sought
Joseph Gwinn kirjoitti: I'm studying up on how IRIG-B decoder circuits work. What are the good approaches, the bad approaches, especially in the presence of noise? (I asked on the NTP group, with little result beyond the C/C++ decoder software written for the audio channel of a 1990s Sun workstation, which it ate alive: 50% cpu load.) I was also searching chips for IRIG-B decoding lately, but didn't find any. Then I decided to create my own, mostly just for fun but there's also some uses for it. So I ended up to use 8-bit PIC16F873 and do IRIG-B DCLS decoding with it. DCLS means logic level IRIG-B signal from Symmetricom TS2100. So it's not 1 kHz modulated. At a start it was only a time code decoder... Then, maybe because very rainy weather in the Finland, new features was added daily. For now, it calculates local time (calendar date and weekday) for IRIG-B day number and year and supports european daylight saving time. Leap second is also supported, if it's encoded in the IEEE1344 control bits (Tymserve TS2100 encodes this, leap seconds are flagged one minute before the actual leap second). IRIG-B timecode is also verified by checking it's continuity. If there's momentary errors or total loss of timecode, timing continues in freerun mode. PPS is also generated from IRIG-B with about +-100 ns. maximum jitter (it's one instruction cycle of 'F873, so it cannot be done better with this MCU). If the whole system is rebooted due to long blackout with UPS batteries runout, TS2100 will jump back to January first of current year. And because TS2100 GPS functionality is now dead, it means that it will also continue with wrong time until it's manually set. Because of that, support for TS2100 resets was also added. Now it keeps record of passed dates on the EEPROM... :) Now I have also DCF77 version of this, where PPS signal is replaced with unmodulated DCF77 timecode with same accuracy than PPS has. I'm planning to use this at least to build some kind of IRIG-B wallclock and possibly to syncronize radio controlled clocks locally with close field magnetic coupling, because actual DCF77 does not work here. However, when testing this I was little bit disappointed when noticed that radio controlled clocks doesn't seem to support leap secods at all. Also their time setting accuracy is not millisecond grade, so the +-100 ns. accurate DCF77 output is little bit overkill when the final setting error can easily seen by eyes... Code is 100% assembler and full version with DCF77 encoder included (and of course with debug LCD drivers) takes only about 1,5 kilowords and needs only 66 bytes of RAM when running. And it's still raining in Finland.. Have to see, what features will be added next.. :) -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] lawnmower robots may be the end of VLF timekeeping
Poul-Henning Kamp kirjoitti: I spent some time capturing some data today. The measurements is from my $20 loop-antenna in the attic, which is something like 8 meters up and 10 meters besides the lawn-mower loop: http://phk.freebsd.dk/time/20150509.html In the Finland that problem is even worse! For me it's called Savon Voima, our local power company (but also many other power companies around the Finland). They are using PLC based remote readable utility meters. These meters communicate with power lines, using ancient 1200 bps. FSK using 83.2/93.6 kHz frequencies. Because the power grid is not designed for this kind of communication, those frequencies will of course leak all over the places. Because the metering hardware is cheap crap made by Slovenian company, those frequencies are not very accurate/narrow and so they block the DCF77 77,5 kHz band totally! Because all in-house wiring act as an transmitter antennas, the field strenghts inside the houses can be as high as 120 dBuV/m. The system is so stupid that it need to communicate 24h to transfer less than six digits (the reading of the utility meter), which is basicly needed once per month for elecricity billing. Every meter can act as repeater to other meters. The DCF77 problem was verified when there was large blackout. During this blackout the DCF77 clocks was syncronized at moments, when they never synchronize normally. When this was reported to Finnish authority called Viestintävirasto (it's Finnish version of FCC), they say that this doesn't matter - the DCF77 is not protected in Finland (even when you can buy radio controlled clocks from the shop). The whole idea about PLC is so stupid and the universal stupidity factor of the people designing these is so high that there's nothing to do anymore. Even the power company said that this is not reliable system, having much of interferences, the readings are not transferred succesfully all the times. But still they buy this kind of crap, even when knowing it weaknesses. Clearly the marketing guys of PLC systems knows their business and they can even cope with local auhorities so that there's no problems to install these everywhere. I think that we have lost the game! Only way to set the clock is to build your own DCF77 transmitter - like the local authority said: the DCF77 band is not protected - at least here in Finland... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Engineering commands for TymServe 2100
Bob Marshall kirjoitti: We have TymServe 2100 units and need the IRIG-B signal. They are disconnected from GPS and running in free mode. I’ve set the time via telnet but can only do that within about 250 milliseconds of the correct time. I see the engineering command “root engineering timing offset_time” but when I try it nothing happens to the time. It's for GPS and maybe also for external fed PPS also (not tested that). Some units, like mine had 10 us error in the PPS output and it was possible to fix this by setting that offset to zero. I have not tested that with PPS because there's no error. To correct a -200 millisec error (reported by ntpq -p) I try: “root engineering timing offset_time 200” (the units are 100ns). According to my own tests I think that command doesn't do anything without GPS or (maybe) external PPS. Only way to get it in time is to feed it with external PPS first, let it lock to the external PPS (having all three leds on) and THEN adjust the time from telnet. But without external PPS there's no point to adjust that 250 ms. error, because it will be there again after couple of days. It won't keep the time very well without any external reference unless it's rubidium based version. Also, when adjusting the time from telnet you may end up always having 1 second offset (because it may be little bit hard to press the enter just correct time). In that case you can use the leap second command to adjust the time. Just program the leap second event to nearest minute change and it will happen then. By doing this it's much easier to remove 1 second error than trying to press return in the telnet just in correct moment. You can add or remove the leap second. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] TymServe 2100 1995 Issue - A Kludgy Fix
Andrew Cooper kirjoitti: We also ran into the TS2100 1995 bug this weekend. For us the consequences are a bit more severe... So this is happening already.. Didn't notice this because have been using PPS from Thunderbolt to keep the TS2100 in time. It failed with leap second already in February (if I remember correctly) so I think if you have same firmware than I have (the most recent one) you have already got 1 second offset from real UTC since February. However, with PPS everything is fine. The unit is not rebooted after February (when removing the inegrated GPS unit) and it's in time. However that's not only bugs TS2100 has. I'm currently creating my own IRIG-B decoder and noticed that there's something strange going on with IEEE1344 checksums. The checksum will fail with random hours and beign ok on others. Seems that hour number is not included in the checksum or something. But that's another story... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS week rollover
Mark Sims kirjoitti: People using Tbolts for things like NTP servers will have to implement a similar fix... I'm pretty sure that many GPS based NTP servers will also fail. For example I have TymServe 2100 and it fails already with leap second handling. Just now the integrated GPS cannot be used until the end of June. Only way to run this baby now is to feed it with external PPS (from Thunderbolt). I'm pretty sure that this will be the permanent solution after 2017. Tymserve's integrated GPS module is from Trimble, so the risk of having same problems than Tbolt is real. We'll see.. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom TymServe 2100-GPS currently fails with GPS offset
Andrew Lindh writes: Use an engineering command to set it to 16: root engineering timing early_utc_leap 16 You can also set the TS2100 to add a leap second at the correct time: root timing leap 1 07/01/2015 00:00:00 Tried that, but it seems that this setting stays only for a ongoing hour. As soon the hour changes, the leap setting will be lost, UTC offset is 17 again and time has one second offset: Before hour change: 27 ? leap leap second insertion at JUL 01 2015 00:00:00.00 After hour change: 28 ? leap leap second none at NOV 15 1995 00:00:00.00 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Fwd: Symmetricom TymServe 2100-GPS currently fails with GPS offset
Tim Lister kirjoitti: Hi Esa, I am forwarding this message as I'm not subscribed to time-nuts list, just a lurker... It's good to know we're not the only ones having problems, even if there is no obvious solution. Do you think there is any hope of getting Symmetricom/Microsemi to release an updated firmware to fix this or are they most likely to turn around and say buy something made this decade... It's possible that they cannot fix this even if they wanted to do so (which I doubt) because it's kinda old product and it may be that there's no engineers anymore in the house who know this product. I afraid that only way to fix the firmware is to do itself. I have a guess that the problem is related to decoding of wrong portions of the GPS frames. So it would be possible to find where the actual command to decode UTC offset is used and change that part of the firmware. This is not easy way at all, but it's possible to do. It consumes HUGE amount of time. First thing to do is to find out what protocol is used between mainboard and GPS. Because it uses Trimble GPS module this could be TSIP (rough guess). To find it out, it's required to install a sniffer between the GPS and mainboard. TSIP protocol specification seems to be available on the Internet. Firmware modification is not easy task to do and it's also dangerous, whole unit may be permamently useless after loading the mofified firmware, with no way to load correct firmware anymore. There's also checksum mechanism to prevent corrrupt firmware and because of that the data content must match the checksum or checksum must be updated. Another (and recommended) way could be to add some simple microcontroller (Microchip PIC for example) between the GPS unit and motherboard and write own software which modifies the GPS traffic so that UTC offset will be correct again. This way also requires some study first but after the details are known the needed software for data modification should be very easy to do. I have motivation to fix this but having no time for this, at least in near future. Quick fix was to feed it with 1PPS from Thunderbolt. However it unconfortable to do this every time when leap second is coming. Also, if the power is lost it will start from January first 2015 00:00:00 and the time must be set manually each time, it does not recover automatically with PPS. That's why it would be so nice to fix this, but without any knowledge of the unit details, firmware source code or GPS protocol it will require many days to do. Best regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom TymServe 2100-GPS currently fails with GPS offset
Robert Watzlavick kirjoitti: I'm seeing the same thing with my TS-2100 - it is one second behind WWV based on the front panel display. My ET-6000 appears to be in sync. Ok - then this is verified... So the only way (for me) is to run this with 1PPS from Thunderbolt. Good thing is that Tymserve itself support leap second and when 1PPS is used it can be set manually. I did some quick tests and noticed that correct command to set the leap second event is: tim leap 1 07/01/2015 00:00:00 SPOLER ALERT - if you want to see the leap yourself, stop reading... It did not go 23:59:60, it was stopped at 23:59:59 two seconds. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Symmetricom TymServe 2100-GPS currently fails with GPS offset
Hi! It seems that there's serious bug in Symmetricom Tymserve 2100 most recent firmware (V4.1). When leap second pending flag was added to GPS transmission (according to data shown by Lady Heather) the Tymserve's time started to be exactly 1 second late from UTC! Currently it claims that current UTC offset is 17 seconds, while Lady Heather shows 16 seconds. Also if I compare the NTP time with another NTP servers it is really 1 seconds late. Playing with telnet: ? utcoffset GPS -- UTC Offset = 17 (And of course there's no way to set this manually) However in the utcinfo data the dTLs value received from GPS is correct (16) but it seems that Tymserver firmware uses wrong value dTLsf, which is the future value of UTC offset after leap second event: ? utcinfo A0:0.000 A1:0.000 dTLs:16 ToT:61440.000 WNt:1829 WNLsf:1851 DN:3 dTLsf:17 It seems that there's no way to fix this. There's also leap second command available, having no efffect on this. Everyone who owns this device please check what's going on with it... To me this is somehow suprising, assumed this to be professional grade, reliable and trouble free instrument, but obviously it's not. No wonder why these are sold so cheap on Ebay (where I got mine). Maybe only way is to run this with 1PPS from Thunderbolt until the leap second period is over. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Setting Windows XP clock.
Hi! At first, Windows XP supports SNTP protocol (so it can be synchronized with NTP server, but not with millisecond grade accuracy) and it uses time.windows.com as default server. Maybe Microsoft is closed that server or something, if it doesn't work anymore. However it's easy to change the NTP server, like Ed Palmer alrady described. It's also possible to use local NTP server, I use Symmetricom/Datum TymServe 2100 to synchronize the system cloks for all Windows computers. Works fine and does not need connection outside local network. Any Windows computer can also act as NTP server, if millisecond grade time is not needed. Registry change is needed to enable the Windows NTP server, Google if you want to do this. In addition, the system running as NTP server must also have working NTP client configuration so that it syncrhonizes itself. But remember, integrated Windows NTP is not very accurate, the time may have even more than ten seconds offsets. You do not want to have your XP box connected to the internet at all. This is not something that can be dealt with by any anti-virus software you are running. I even have Windows 2000 computer having 24/7 internet connection. This is a server computer running 24/7, doing certain tasks. Windows 2000 support is stopped many years ago and also there's not even anti-virus software compatible with Windows 2000 anymore. Sounds dangerous? Not necessary - there has not been any trouble ever... The secret is that this (and all other computers) are behind NAT firewall so there's no direct access to this (or other) Windows computers. Second thing is (maybe most important), that this computer is NOT used for any web browsing or e-mails (which are most common way to infect any unprotected computer). By the way, XP support is not fully stopped yet, there's still monthly malware removal updates coming. Last one happened just few days ago. We still use XP for work (with anti-virus software of course) and there's never been any problems with it. Any suspicious traffic from local network to the Internet will be noticed by network monitoring, but there's haven't been any. XP is safe, if it's behing network firewall. One easy trick to keep any Windows computer safe is to use Jotti's Malware Scan service before running any new .exe files downloaded from Internet: http://virusscan.jotti.org/ This is an easy-to use online service, where you can send files for scanning. It uses more than 20 anti-virus tools to scan the file and reports the results from each tool. If the file is infected, there will be many alerts, even when the anti-virus software installed in own computer doesn't give any alert. Connecting any Windows computer directly to the Internet (without NAT or nework firewall) or DMZ is not recommended at all, even if it has most recent Windows version. There will be always new and undetected vulnerabilities. That's the reason why the Windows updates exists. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Is there any IRIG-B hardware decoders available?
Hello! What is needed now is to decode IRIG-B timecode and syncronize the system time (or hardware timer) to it with about 1 ms precision. Operating system is Linux based and runs on embedded environment. It should support both, AM modulated and digital pulse versions of IRIG-B (for now it's unsure which will be used). Is there any IRIG-B decoder chips or reference schematics available with full support for the standard? Google didn't find any ready solution for this need. It looks like only way to get this is to design it from scratch... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Is there any IRIG-B hardware decoders available?
Chris Albertson kirjoitti: NTP will so this. There is an IRIG reference clock. You really do want to use NTP to discipline the PC's clock. Almost every other method is worse and causes time discontinuities. If you happen to have TTL level IRIG it s very easy to convert it to amplitude modulated IRIG. The standard is a 1KHz tone. Build a cheap 1KHz oscillator. A 555 timer is good enough. Then you a single transister if IC time switch to modulate the amplitude of the signal. The details are not critical. That's good idea if the phase of the 1 kHz signal is not critical? I checked the IRIG-B signal with oscilloscope and looks like the 1 kHz signal's phase is locked to the time signal. The bits will always start and stop at exactly same phase. That makes sense because with phase detector it could be possible to get very accurate timing from the 1 kHz signal - much better than following the amplitude only. That's one reason why I was interested about chipsets; if they can follow the phase also. I think if I design any hardware for that it should follow the phase also? It may be complex... Does anyone know if the soundcard based IRIG decoder will follow the phase also, or only the amplitude (?) -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Symmetricom TS2100-GPS - 1PPS has 10uS offset
Jason Rabel kirjoitti: I think nobody ever really bothered to fix anything since the NTP time was good enough. Yes - definitely... If it's only used for NTP then the 10 usec error is totally insignificiant. NTP solution seems to be quite inaccurate, if I poll my server from http://support.ntp.org/ntpq.php the results can vary couple of milliseconds every time. However the offset shown by test page is always less than 10 milliseconds. Maybe this is because the route is too long: delay is more than 230 ms - the test site is far side of the world for me... It' the nature of the TCP/IP and Internet that the delays are quite random. Same result if I set up software NTP server which polls many NTP servers from the net. The results are always vayring many milliseconds and the server will constantly change the best server to follow. I think the multitasking operating system will also add some errors to the ntp server operation, since the internal system delays will always change as well. The hidden eng menu does have some interesting stuff. I've tweaked the offset to bring time in sync with my other NTP servers, usually around -4000 does the trick since the TS2100 doesn't use a true NTP implementation (I think it is more SNTP). According to manual it should support both protocols, but maybe this NTP vs SNTP is more like client side difference? I understood that NTP polls many servers to get kind of averaged timing, when SNTP uses only one server. For example Windows has SNTP only, you can define only one time server to use at time. Well of course TS2100 doesn't poll any servers and uses only one time source, GPS. I have seen different offset settings in units, so I would think there would be *some* way to save the setting, but like you have not found out a way to do it yet. :( Yes! That's now the only question... If this will remain unknown, then maybe I will setup a microcontroller connected to the console port and set it to follow somehow, when TS2100 is restarted. Then it could send the eng tim offset... command via serial port to restore the offset setting automatically every time when needed. This is quite stupid way to store the setting, but it might be the only way if the offical way to store the settings will remain unknown. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Thunderbolt leap second video
Leap second capture of Lady Heather screen. Select 720p to see it properly: http://www.youtube.com/watch?v=DbvMZikqtI4 -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Leap second coming...
Does the Lady Heather / Thunderbolt show the leap second? It's present in the alarms but can you watch/log the 23:59:60 event with this setup? Regards, -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Prologix GPIB-USB vs. GPIB-LAN
If it's about Ethernet vs. USB queston I would always suggest Ethernet. - With any kind of equipment in question! Ethernet is simpy much better: you don't need device drivers, it works with longer cables (over 10 times longer than USB), it's routable, you can use it remotely (VPN), you can turn it wireless (WLAN) and because there are no need for drivers it's much more platform / OS independent than USB. USB is good for devices which can draw their power from USB port, like mices or keyboards. But it has many drawbacks: some USB devices won't work with Windows Vista. Some USB devices has stupid drivers which need to be installed for each USB port in the computer. I'm talking about the issue when you install a driver and later plug it into different USB port the system will ask you to isntall the driver again. Also, many USB devices based on some kind of USB-Serial chip (like FTDI) may have different COM-addresses for different USB ports and this leads to same kind of issue: it works only with one USB port witout changing some settings. In the worst case you must remember the corrent USB port for each device. With Ethernet it's not essential which port (or to which switch) you plug in your device, as long the switch you are using is a part of your local network (or there is VPN remote connection to your network). But... of course this in only my opinion. :-) I have used the Prologix (LAN version) with KE5FX GPIB toolkit. You can use it for capturing plots from oscilloscopes, spectrum analyzers etc. and write some kind of command scripts for the instruments. Maybe it's not best possible software for Prologix but it it's free. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Bruce Griffiths wrote: Attached circuit schematic illustrates how you could filter the harmonic content of the 10544A below -50dBc. Ok that's something what I can't build from shelf parts anomore... What kind of coils should be used here? The transformer may be tricky, I think only way is to build it but first it's needed to find right kind of core. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Hello! I am back home now and can't access the amigazone files from my home IP. Can you provide access? You should now have access. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Hi Bruce... Try increasing C2 and C8 in the white emitter follower circuit schematic to 100nF. Doesn't seems to change anything: http://www.amigazone.fi/files/gpsdo/544-15.png http://www.amigazone.fi/files/gpsdo/544-16.png When doing this measurement I noticed that the 3rd and higher harmonics level are changing! First I thought that the capacitor change was some effect on harmonics but then those peaks come back... Time domain analysis about 3rd harmonic level gave some explanation: http://www.amigazone.fi/files/gpsdo/544-17.png The EF circuit was turned on at start of sweep. Something is heating and raising the harmonic level. The bump and the end of sweep is a test where I momentary switch off the 12V feed to the EF circuit to see how it reacts. Temperature sensitivity was also verified with cold spray: http://www.amigazone.fi/files/gpsdo/544-18.png Well, that's not an issue but makes measurements harder because even without any changes the results can differ. However the temperature effect on the 2nd harmonic frequency was very small. The switcher sidebands will still be there, they are just buried in the spectrum analyser noise floor. Yes you're right. Just changed some settings and there they are again: http://www.amigazone.fi/files/gpsdo/544-19.png About 90 dB below carrier.. I would say that it's good enough! The LPRO for example, gives higher spuriouses, but far away from fundamental. Does the board use the recommended LC filters and regulator for the oscillator supply as depicted in Figure 3 on the 10544A data sheet? I haven't analyzed it fully but it seems to be just the datasheet circuit having LM723, 10 uH coil etc. But it's layout is totally wrong because oven switcher current runs via wrong trace. It would also been possible to have other side as grouding copper but this was not done. The PCB is manufactured by Cubic western data. The required parts shouldn't be too expensive, however you may need to wind your own inductors for the series tuned LC circuits. Air core or powdered iron core inductors should be OK as long as you use shields between filter sections etc. Sounds like hard. How it's possible that lower grade ocxo's (like in thunderbolt) output so much better spectrum? Is it all about ocxo output driver circuit? Would it be easier to modify the 10544A itself than trying to clean the distortion? Has anyone tried that kind of modification? -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Hi Bruce, White emitter follower circuit attached. Here are the results. First, the circuit draws 33.3 mA at 12 vols. And it's gain is 1:1 as expected with emitter follower - checked that with RF generator as an input just to make sure that I built it correct. With HP10544A the output level is below +8 dBm: http://www.amigazone.fi/files/gpsdo/544-10.png (with 2 meters of RG174 and SMA-connectors between the circuit and SA) Now the harmonics look like this: http://www.amigazone.fi/files/gpsdo/544-11.png And 2nd harmonic level: http://www.amigazone.fi/files/gpsdo/544-12.png So the spec told that 2nd harmonic should be more than 25 dB down, it is just in spec... So the final result looks that the 10544A is OK but it really has this kind of output spectrum? -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Since retrofitting an improved oscillator circuit isn't really an option you will need to filter the output to reduce the harmonic content. Try a bandpass filter driven by the buffer and terminated in 50 ohms. Well I have to decide what to do, get another oscillator or try the filtering. The difference to another oscillators (like tbolt ocxo or LPRO) is so huge that I do not know how hard it would filter the 10544A to the same level, which parts to use and how much it will cost. Should you retrofit an improved oscillator circuit you may as well replace the oven controller to eliminate the oven switching frequency related sidebands. Infact the switcher sidebands are now gone: http://www.amigazone.fi/files/gpsdo/544-13.png http://www.amigazone.fi/files/gpsdo/544-14.png It was like thios earlier: http://www.amigazone.fi/files/gpsdo/544-1.PNG http://www.amigazone.fi/files/gpsdo/544-2.PNG It was easier than I expected... When I took the output directly from OSC pins without using the coax connector like you suggested the switcher peaks was gone! So I had a closer look to the PCB today and noticed that it has only 2 layers and the ground net is too thin and goes around PCB totally wrong way so that switcher current seems to flow via the signal flow. It's PCB layout design fault, I think that with correct layout design this could be done even with 2-layer PCB correctly. But this is not a problem of course because I will design my own PCB for the final system anyway, having SMA connectors for 10 MHz and EFC. I'll also create separate power supply for ovens and signalling stages. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
5370A: 1K + 10pF in series connected from 10544A output to input of an ECL line receiver cascade. 5345A: 1K + 910pF in series connected from 10544A output to input of CC CB long tailed pair isolation amplifier. 1K from CC base to ground. What do you think: if I would be able to create perfect buffer for it somehow will it still have worse spectrum than tbolt ocxo for example? With capasitive coupler test the 2nd anr 3rd harmonic was still high. Maybe it's the best what it's possible to get with 10544 anyhow? So is it even reasonable to try or just get some other ocxo? I would like to have as clean 10 MHz as possible with reasonable price. Let's say that the spectrum what tbolt ocxo gives could be some kind of minimum. But I'll need that ocxo inside thunderbolt in it's original place. Since the 10544A phase noise floor is relatively high (~ -145dBc for the later variants earlier versions had a significantly higher noise floor spec) using 1K in series adds little additional noise. Is it so that 10544A isn't good for RF lab reference at all? Maybe it's designed just for counters etc. where the spurious or harmonics are not so big deal? Unfortunately I'm so rookie with these that clearly I'm seeking wrong stuff. At very first I expected to have a good 10 MHz reference with just using thundrbolt but then noticed that it's for time, not frequency reference. Maybe 10544A is intended for timing applications also, not as frequency standard? -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Hi Bruce A more efficient buffer like a white emitter follower using 2 x npn + 1 x pnp would be best. If you want I can post such a circuit using BC546 + BC556 or similar. Yes if you have that kind of schematic I'd like to test it. It won't take much time to do breadboard testing. I have BC547's and BC557's ready in the shelf, all E12 resistor values are available but capasitors and coils are not so easy; of course any standard values like 100n, 10n, 22...33p etc. are available at a moment. Coils are most difficult however LCR meter is available but I don't have any cores that might be necessary to make coils for this purpose? This buffer needs to be located with 5cm or less of the OCXO connector unless you use capacitance cancellation techniques. Ok.. there was a bottom PCB used all my previous tests, which itself has about 5 cm. trace before coaxial connector. I don't know where this PCB is originally used. It included 12V regulator and some filtering. But maybe i could get the signal directly from output pins without using a coax at all, with just a pair of very short wires and take the OCXO as close as breadboard as possible. First you need to decide what output level you want: +7dBm? +13dBm? Many instuments seems to want as much as 1V input for external reference. That seems odd because the level is so high that it will cause a 10 MHz spurious peak easily. So I think the +13 dBm should be enough. There will be some kind of distribution amplifier in final design and I have no idea about it's gain (not selected any yet). But let's assume it will have gain of 1:1. The how far do you need to suppress the 2nd and 3rd harmonics? There's no specification for these. But if we think about the application which is to clean the LPRO's output signal it would be nice to have at least same kind of harmonics performance that LRPO itself has. It has some kind of lower grade crystal inside but I have no idea maybe there are some filtering because the spectrum is fine: http://www.amigazone.fi/files/gpsdo/LPRO-3.PNG Some spurious on 50 MHz and below 150 MHz still present. You need to set some actual specs. I think good spec is that it has to clean the LPRO's output, not get it worse. I know it's main purpose is rubidium noise cleaning, which is not seen in these spectrum measurements at all and I even don't have the cleaning loop yet. I'm trying to pass on step by step so first thing is to find out how to generate a good 10 MHz signal and next thing will be that (digital?) phaselock needed to lock that on rubidium at suitable timing constant. Then there will be another stage to control LPRO's C-field with GPS, some diagnostics, power supplies, distribution amplifier etc... Lot's of work to do. Infact I had no idea how hard it is to get just a clean 10 Mhz... Attenuating them by 20dB is easy if you need to suppress them much further it gets more difficult. Yes that's the point I'm afraid with 10544. Don't use a high Q bandpass filter as its phase shift tempco will be relatively high. What do you think if I could find FM radio IF filter somewhere (10.7 MHz) and tune it to 10 MHz? I don't know if there's tunable filters available anymore because any new ones seems to be ceramic. But maybe from some old radio could have tunable one (wishful thinking in Finland, thanks to recycling of the electronics). -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
White emitter follower circuit attached. Ok and thanks, Bruce! I'll test that later. Now it's family time.. :) Distortion of this circuit is lower than that of the 10544A. Ok it would then give the actual output spectrum of HP10544. Would you do the test with or without the 1000 ohm. termination before C1? The datasheet recommends the 1k termination but how with this kind of amplifier? -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] About HP10544A
Hello! I got one of the 544's and plan to use it for rubidium cleaning loop (Efratom LPRO). But I cannot get a clean 10 MHz signal out from it! There are harmonics and spurious. I know that spurious come from oven swicther so those should be easily handled with separate oven supply. But the bigger problem are the harmonics: http://www.amigazone.fi/files/gpsdo/544-4.png This spectrum is measured with emitter follower buffer connected to output which is terminated with 1k like datasheet recommends. So the load should be ideal but still distorted. The distortion can be seen even with oscilloscope: http://www.amigazone.fi/files/gpsdo/544-6.png So it ooks like negative half cycle is distorted. As a reference, THIS is the signal to be cleaned with HP10544A: http://www.amigazone.fi/files/gpsdo/LPRO-3.PNG :-) So... I believe that there may be something wrong with HP10544A if it's output is worse than lower grade xtal oscillators used in LPRO etc. But just to make sure I'm asking you guys having these oscillators. Should it even give clean sine wave or not? And if it should, where should I start to seek the fault? -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Hello.. I tried to view the files on amigazone but was 'denied'. Yes there's many network bans and all thanks for this belongs to couple of spambots trying to scan the webserver at multiple IP's at same time. I just changed the IP bans based on IP address where you send your mail. You should now have access. Can you see the pictures? Any way to get a look? Am I doing something wrong? You are not doing anything wrong but someone else does with their spambots... :-( I have several 10544A's and they all put out a 10 MHz signal but it is sort of a 'ramp like' wave as viewed on the oscilloscope that looks rich in harmonics. My 10811's seem to have a pure sine wave though I have not looked at it on a spectrum analyzer yet. Oh no.. then it could mean that 544 is no good for that project... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
New 10544A's have a somewhat cleaner output than that. Perhaps something is wrong with the emitter follower. Sorry I forgot to say that the oscilloscope picture was taken directly from HP10544A output, without emitter follower but with 1:1 probe, output terminated with 1 kohm. resistor. With spectrum analyzer the emitter follower is necessary due to 50 ohm. input impedance of the analyzer. Datasheet of HP10544A claims that harmonics should be more than 25 dB down. Doesn't look like they are. Here's a spectrum measured from OCXO which is used in the Thunderbolt. I'm not an crystal oscillator guru but I think that this is just what an xtal oscillator output should be: http://www.amigazone.fi/files/gpsdo/tbolt-1.png http://www.amigazone.fi/files/gpsdo/tbolt-2.png -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
The capacitance of the 1x probe is too high. So I have to check that also: it shows 46 pF on 1x mode and 10.6 pF in 10x mode. Ok so the main question is that what kind of amplifier I should use with 10544A to get a clean signal, if it can't stand even an oscilloscope without distortion on it's output? And what do that kind of amplifier cost - more than HP10811, for example? Many other OCXO's (like thunderbolt's) can be connected directly to the 50 ohms. load without any trouble with harmonics. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Please provide a circuit schematic for your emitter follower buffer. Include transistor types and component values as well as power supply voltages. 10nF DC-blocks at input and output, 4k7 pullup and 10k pulldown at the base, 180 ohms pulldown from the emitter, 12V input voltage having some 100n coupling capacitors. BC547 as transistor (should do 250 MHz?). I built that from schematic of 10 MHz distribution amplifier but with dirrefent transistor (there was BC849C in the schematic) and without LC-filters at output. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
I also doubt that there could be something wrong with emitter follower so I also did some tests with capacitive coupler build on bottom PCB of the HP10544: http://www.amigazone.fi/files/gpsdo/544coupler.jpg (1 kohm. terminaton is not visible on the picture) Generally it's just a wire going over 10 MHz trace on the PCB and then it's connected to the spectrum. By this way it's possible to measure the output without loading it with any galvanic connection. Of course there is almost 30 dB of loss but it's not any trouble with spectrum analyzer having over -145 dBm noise floor. But with that kind of measure the output specrum looks like this: http://www.amigazone.fi/files/gpsdo/544-5.png So there's less harmonics but 2nd and 3rd are still high if compared with other OCXO's. Hard to say anything of higher harmonics because that kind of coupler takes in all background noise like FM broadcasts etc. so I wouldn't trust these measurements too much (and because of that I didn't even mention them at first). -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] About HP10544A
Its probably better to increase the emitter current to 40mA or so and place 47 ohms between the emitter and the output coupling capacitor a and accept the resultant +7dBm output. The transistor dissipation will increase and it may be better to substitute something like a 2N5943, 2N3866, 2N 5109, BFW16A or similar. I don't have those 2N types but after some digging found 2N2219A. Changed that and 47 ohms from emitter to the ground. I run it first with 6 volts, then with 9 volts and then with 12 volts but have to stop with uncomplete sweep because it become very hot. Increasing the current does help with amplifier linearity but not so much. However the spectrum looks little bit better now but it's still out of spec: http://www.amigazone.fi/files/gpsdo/544-7.png http://www.amigazone.fi/files/gpsdo/544-8.png http://www.amigazone.fi/files/gpsdo/544-9.png About the only way to achieve the distortion you observe is if the capacitance of the wire connecting your emitter follower to the 10544A output is too large (around 50pF or more). It's about 30 cm. long microwave coax taken out from some RF stuff (maybe old cellphone). It's measured capacitance (at the other end free) is 36,2 pF. I'll send the picture later if still needed.. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Some results of Tbolt + LPRO case
Hi! Although this will not be my final setup the measurements had already started with Tbolt OCXO replaced by LPRO and are now done. I think some of you might be interested of the results. Here's some Lady Heather logfiles and couple of pictures. Unmodified Thunderbolt in my place (many trees at the yard etc): http://www.amigazone.fi/files/gpsdo/tbolt-default.log http://www.amigazone.fi/files/gpsdo/tbolt-normal.jpg (Includes short holdover test at the end) Unmodified Thunderbolt in holdover mode: http://www.amigazone.fi/files/gpsdo/tbolt-holdover.log Unmodified Thunderbolt OCXO performance (disciplining off): http://www.amigazone.fi/files/gpsdo/tbolt-ocxo-freerun.log OCXO now replaced with LPRO, normal run: http://www.amigazone.fi/files/gpsdo/tbolt+lpro.log OCXO replaced with LPRO, disciplining turned off: http://www.amigazone.fi/files/gpsdo/tbolt+lpro-freerun.log http://www.amigazone.fi/files/gpsdo/tbolt+lpro-freerun.jpg This final test simulates my planned setup (without final cleaning loop however). Next thing is to try to get some ADEV charts with Ulrich's Plotter. For some reason it shows only e-1 values for now, the actual shape of the trace looks ok. Have to learn about the settings... -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Home made GPS disciplined atomic clock
Esa, the answer to your problem is, as I said before, to clean up the signal, use a high quality oscillator locked to your system with a PLL that has the appropriate time constant. Yes. My problem is to find time constants, with measurements and that's currently under work with GPS, later with LPRO. I've done some HW and SW planning also. It could be like this: - Tbolt is used to synchronize LPRO with own designed steering system. - LPRO steering time constant will be long, let's say 24h or something, to cancel out any day/night variations (if any) on GPS reception. - The goal for LPRO synchronization is to have constant frequency, not exact time. This will ease the LPRO steering algorithm and there's no need to catch up the exact time by changing the output frequency (like tbolt always does). - Own steering electronics will constantly monitor the state of tbolt with serial port. If holdover is detected then the LRPO steering will also be stopped and averaging loop will be reset. DAC remains as it was. - When the holdover is over the running averaging will be started again but C-field DAC will remain as it was until there's enough data for last 24h to do some C-field corrections. - It might be a good idea to reset the steering also if the frequency error (ppt value) of Tbolt's 10 MHz output is detected to be too high. - Steering MCU uses LPRO as it's clock because it will count it. MCU's HW peripherals like counters and capture unit is used to handle the 10 MHz count, the software just reads out the counter values occassionally. - The counters are read only every n'th:s PPS so that mHz resolution can be achieved without using external frequency multipliers etc. Also the PPS drift will be averaged this way. The n could be at least 3600. - These counted values are used as input data to running avg having a long time constant such as 24h or even more. - So the period for DAC changes will depend how long counts (in seconds) is done at first stage. It's sure that the DAC won't be changed here in about every second like Tbolt does! - Then LPRO's output is cleaned with Wenzel or some other OCXO, with suitable time constant which has to be find out. Phase detector and good reference OCXO is needed for that. May be it's wise to buy only one OCXO and use it for measurements frist and then as output oscillator for final setup. - Finally there will be some kind of distribution amplifier for 10 MHz. So it will be slow to settle but should be good enough for stable 10 MHz source. I think it will have good long term stability due GPS, good holdover performance and if the final OCXO cleanup works as excepted there will it should also have good short term stability. Much work to do but for now this is only a hobby project. The time constant will smooth out the jumps you see right now. The question is only which oscillator. A Wenzel was suggested but in my opinion it is not what you need. The output phase noise may be not so bad issue as it sounds like. It seems that some RF instruments (like my spectrum analyzer) have their own clean up loops for external ref. Only problem is that their time constants are unknown. But it's in there - at least in spectrum analyzer; checked that from service manual yesterday. I have used a Wenzel because I wanted the low phase noise when multiplied to 10 Ghz. In these days my maximum needed frequency in about 5.2 GHz so any error on 10 MHz ref will be multiplied by 520. For that reason I also want CONSTANT frequency, it's not so bad if it's off ±1 mHz at some day but it's very bad if it has different frequency error between measurements done on same day. So I'd like to drive that DAC as rarely as possible and as little steps as possible. May be even only one correction per day, done at nighttime when there are no measurements on going.. There will be LCD screen for status so it could also told the actual frequency difference to averaged GPS reference but without any DAC changes if they are not desired that time. plenty of oscillators out there at a reasonable price starting with the HP 10544. Yes, the 10544 will clean up your present setup and will be at least a 10X improvement over the LPRO solution. But the most widely available unit is the HP 10811 which will do a great job. Haven't seen those available here in Finland. We have much too fanatic recycling on going on Finland and so even fully working electronics are doomed to be destroyed (shredded to get the metals out of them). One friend has seen his own eyes the destroying of only couple of years old servers etc. Madness! And any plastic material remained for this process is dumped as huge lumps for next generations. Saves nature indeed! All thanks to this goes to one company which just want to recycle metal and export it to china. So there's no such treasures
Re: [time-nuts] Home made GPS disciplined atomic clock
Hello again... Right, it all depends on what stability you're after. The OCXO will have much better short-term stability than the LPRO -- the LPRO is close to ten times worse. So do not replace the TBolt OCXO with a LPRO if short-term stability is your goal. See: I'm wondering what could be the cause of this. According to operating manual LPRO's output should be crystal oscillator (VCXO) generated signal, which is synchronized to rubidium. So why it is so much worse than any other crystal oscillator (or other Rd oscillators). Are there any schematics for LPRO available anywhere? I cannot see the any phase noise difference between Trimble's OCXO and LPRO with spectrum analyser. Measured with different spans from 500 kHz to 200 Hz, using resolution bandwiths 300 Hz to 6 Hz. So the noise which is causing bad short term drift must be very close to fundamental. It seems that only way to see this noise is to use phase detector circuit but my problem with that is that I haven't got any good reference for it and this kind of equipments are quite hard to find here in Finland. It would be nice to see what kind of noise there are, to design the filter bandwith for external OCXO lock circuit. Other idea to bring that noise visible could be multiplying it with some kind of comb generator circuit (might be hard to build one). Then it would be possible to measure it's harmonics. Not sure if there's enough level present anymore at GHz frequencies... What kind of test setup did you use when getting this result: LPRO plots: http://www.leapsecond.com/museum/lpro/ -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Home made GPS disciplined atomic clock
Its relatively easy to assemble such a system. A PC sound card can be used as a spectrum analyser for measuring phase noise to within a few Hz of the carrier. I still need some high quality reference oscillator. Do you have any clue how much those Wenzel oscillators cost? There wasn't any prices on website, may be the only way is to ask? There seems to be interesting alternatives for the output oscillator too (to clean the LPRO signal). One of those was even named timekeeper. Maybe it could be wise to buy one and use it for phase noise measurement first and then put it in permament use as the output oscillator of the reference, when the desired loop bandwith is known. But of course if those units has price tag with four figures or so then this is only daydreaming... :-) -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Home made GPS disciplined atomic clock
If you have an older PC/laptop that can run DOS or WIN98 and has a VESA compatible video BIOS then you might want to try Lady Heather's Disciplined Oscillator Controller Program (downloadable from the archives). It has bulilt in support for calculating and graphing the ADEV/OADEV of the PPS and OSC parameters. Also graphs the PPS and OSC values along with the DAC and TEMP parameters and the satellite count. Constellation changes are also marked. Thanks again. Just tested that (runs also with XP DOS mode) and it's great! Have to set some older laptop for this. It even shows me that the Kalman filter was still OFF, that information seems to be missing in tboltmon. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Home made GPS disciplined atomic clock
Right, it all depends on what stability you're after. The OCXO will have much better short-term stability than the LPRO -- the LPRO is close to ten times worse. Basicly I'm seeking an accurate frequency standard for RF lab. It should be always as accurate as possible, regardless the state of GPS receiving etc. Before doing this modification I did some test runs Trimble versus LPRO with phase comparator circuit. I noticed that Trimble is accurate as long as it gets the GPS signal and phase change between LPRO and Trimble was changing evenly. It is even accurate after the GPS drops (holdover mode) but after the signal comes back the things start to go badly wrong. It starts to roll it's phase / 1 PPS back to alignment woth GPS time and this caused very badly looking phase activity when compared to LPRO. Another bad issue was that if there's a change in satellite receiving (satellite hopping or some) it causes rapid change the PPS offset and OCXO frequency starts to roll to get the 1 PPS back to alignment. So it seems that Trimble's main principle is 1000 pulses per PPS, with no exceptions and when the PPS goes off the 10 MHz must also go off to get the 1 PPS back to aligment. So there's no constant 10 MHz frequency either. That's not acceptable because in normal use I should be always aware of GPS receiving states - I'd just like to trust that I'm getting accurate 10 MHz - any time! So I become to think that may be very slow loop dynamics will solve that problem (if the DAC value isn't changed at every little change at satellite reception). And for that purpose the rubidium sound better than OCXO. I also got misunderstanding from this: http://www.ptsyst.com/GPS10RB-B.pdf It claims that rubidiums will have good short therm drift. My problem here is that there's no way to measure the different setups because my only rb is now part of the experiment. All I can do is the log them and look the change between PPS timing offset readings. When doing the GPS vs. LPRO phase comparison told before I noticed that the changes of PPS offsets are correlated the phase changes between LPRO and Tbolt output, when observed quite short time. So it seems that the PPS offset is somehow accurate measurement of oscillator stability as well. I also done some noise measurements with spectrum analyzer between LRPO and Trimble outputs. LPRO had lower noise floor around fundamental. See John Miles work to replace the Thunderbolt OCXO: http://www.thegleam.com/ke5fx/tbolt.htm Hmm. May be the OCXO on my tbolt is then somehow bad if the LPRO should be even worse? It has Trimble label on and the unit is manufactured on 2005, in China. Is there any logs available with that better OCXO? It would be nice to see the PPS offsets variance between readings with that oscillator. http://www.amigazone.fi/files/gpsdo/tbolt-lpro-test.log I'll have a look at this; but it's not accessible for some reason. Oops.. Now you should get it. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Home made GPS disciplined atomic clock
Do not forget the Trimble was never intended to be a frequency standard. Ok, then it might be a better idea to use only it's 1 PPS output to count the frequency of the some other oscillator and build own steering electronics for that. Infact my original plan was to do right that. If the count/steering period is set long enough there should be any problem caused the satellite hopping or such things anymore. Let's say that if I make 24 hours running average for 10 MHz using Trimble's 1 PPS as a reference to determine the oscillator control then I would get the better results, right? But if LPRO is useless, which oscillator should I seek for main output? With low short therm drift and good phase noise characteristics etc? Also the goal is to build the reference with surplus (etc) parts as a hobby project, no interest to invest thousands for that. -- 73s! Esa OH4KJU ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
