Re: [time-nuts] Rack-mounting an LPRO?
Hi Paul, The bottom of any rack case is not a good heat sink (heat rises and there is no airflow). I'd put the LPRO on a L shaped aluminium bracket (thick as possible, I got extruded alloy angle cut-off's from a engineering Co once) close to the rear of the case. The longest edge should run along the back of the case. Then bolt through to a heatsink with vertical fins on the rear of the case. Heatsink compound (DC-340 or similar) on all mating surfaces. Robert G8RPI. --- On Sat, 27/2/10, Paul Boven p.bo...@xs4all.nl wrote: From: Paul Boven p.bo...@xs4all.nl Subject: [time-nuts] Rack-mounting an LPRO? To: Discussion of precise time and frequency measurement time-nuts@febo.com Date: Saturday, 27 February, 2010, 22:30 Dear time-nuts, I've just bought a used LPRO-101 which should get a permanent home inside an instrument rack. I've also found a very nice 1U high metal case, and a fitting 24V 1U power supply - leaving plenty of room for a distribution amp and a microcontroller to log things like lamp and Xtal voltage. The rackmount enclosure is 1U high, and seems to be made of 1mm thick galvanized steel. Would that make a good enough baseplate for the LPRO? Would I need to do anything to improve the thermal contact between the rubidium oscillator and the baseplate, and if so, any recommendations on what to use there? The LPRO User's guide and integration guidelines recommend 2degC/W thermal resistance (for up to 50degC ambient), and using some special thermal tape that will probably be very hard to get at these days. If any of you has already put something like this together, I'd be very interested in your suggestions. Regards, Paul Boven - PE1NUT ___ 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] My DIY frequency counter and a request for help
I have had a few replies, both on list and off list, including some offers for help and some suggestions regarding the capabilities of my counter. Thanks to everyone who took the time to write. I understand from various replies I had that I cannot measure ADEV the way I thought I could. I am an electronics man, not a mathematician (or should that be mathemagician?). Adding the ADEV was an afterthought and I'll leave the development of that for now. Magnus sent me the most detailed list of questions and suggestions. I think that by answering his post I cover most of what others have asked me as well. Regards Gerard Magnus Danielson wrote: Would you consider to disclose your architecture somewhat more? In broad terms: Input conditioning with ADCMP600 comparators followed by FF divide by 2 to get a 50% duty cycle signal on both the ref and input channel. PIC micro as time base generates 0.2 ms start pulses, cleaned up with a FF. Output of this FF is start signal to the TDC. Synchronisation with the input signal using a few more FFs, generating a switch signal on the next rising edge. This switch signal is used to switch between counter A and B (two more PICs) and is the stop signal to the TDC. I also have the inverse of the input signal available. By switching on the normal signal and counting the inverse signal I can make sure I never get the wrong count in a measurement period (hence the need for 50% duty cycle). A fourth PIC communicates with the TDC and controls the communication channel via an FTDI USB interface chip. Internally the counter works with a normal serial protocol at 1MB, on the PC side it uses FTDI's D2XX driver to process data in burst mode as opposed to RS232 mode. Each time stamp consists of 10 Bytes. 2 for synchronisation, 4 for the count, 4 for the time stamp expressed as a multiple of the TDC clock period of 200ns (5 MHz). The TDC is an ACAM TDC-GP2. After each measurement it performs a calibration to the ref clock provided (5 MHz) and gives an output as a 32 bit fixed point number with 16 integer bits and 16 fractional bits. So, apart form the TDC these are all cheap off the shelf components available from any electronics distributor. Could you output time and event values from the time-stamping? Would allow us to do some off-line processing independently. I'll work on that. I need to get some data logging functions build into the software anyway. Give me a few days. Could you try different frequencies/amplitudes (would be good for establishing the slew-rate dependency, i.e. internal noise). Measure period jitter and plot for different slew-rates (frequency and amplitude), use shortest tau possible. Will do. I am bit limited in what I can generate at the moment. That screen shot was the output of a HP8922H used as a signal generator set to 10.00 MHz. I guess there must be time nuts on here who recognised the frequency of 10 000 000.461 Hz. If I select 11 MHz I get 11 000 000.461 Hz. At 100 MHz I get 100 000 000.461 Hz. Must be the way the synthesiser works internally. (BTW, this matches what I get on my 5384A counter). I'll have to get the data logging sorted before I can take this much further. Could you hook up the reference clock with different lengths of coax cables. This would assist in measure the background noise and the different lengths of cables would allow some indication of interpolator non-linearity and input cross-talk. Will do. I have now written some software which calculates the standard deviation of the time stamps. If I connect the ref frequency twice than ideally this should be zero. In reality it shows the noise of the whole set up. I have noticed already that by disconnecting and reconnecting the input side I can get my counter to work in two different 'modes' with regards to the calculated standard deviation of the time stamps. My guess at the moment is that this depends on whether the two input dividers are in or out of synch but I need to do some more testing. Good excuse to upgrade my oscilloscope and other test equipment. Interestingly, both 'modes' give me a stable 11 digit readout of my 10 MHz reference frequency at 1 second gate time. The higher SDEV indicates more noise, but it must be fairly well behaved noise not to affect the frequency readout. As has already been discussed, software can do a lot for improving the reading, but one needs to be careful in details or else completely different measures results and they does not behave correctly. ADEV and friends wants the raw time-samples. Frequency or period estimation benefits from improved estimators, but then that is not useful for ADEV and friends, so it is a dead end for further processing except presentation level. I'll keep it for novelty value, but won't put too much more effort into this. I think I have a fairly good setup including bunches of rock, gas and air clocks alongside a fair set of counters, so I
Re: [time-nuts] Rock, gas, and air
Bob Camp wrote: Hi The winds in Sweden change directions in a *very* predictable fashion? Ghaa! Our secret is out! :) No, by rock I mean crystal, gas is Rb and Cs but could also be H but I don't have one of those babies, and by air I mean GPS or other radio-signal. Cheers, Magnus ___ 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] Rock, gas, and air
Quoth Magnus Danielson at 01/03/10 19:36... No, by rock I mean crystal, gas is Rb and Cs but could also be H but I don't have one of those babies, and by air I mean GPS or other radio-signal. Well if you think of radio signals as energy, how about: Air:Rb, CS (gas) Fire: Radio/GPS Earth: Crystal Water: ? Clepsydra? -- Matthew Smith Smiffytech - Technology Consulting Web Application Development Business: http://www.smiffytech.com/ Blog/personal: http://www.smiffysplace.com/ LinkedIn: http://www.linkedin.com/in/smiffy Skype: msmiffy Twitter: @smiffy ___ 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-nuts Digest, Vol 67, Issue 184
Because some people do not seem to know how to trim email, so their individual reply mail to the list, also contains the entire digest they just received! Not just the mail they were replying to. Sheesh... Dave B. Original Message Most mailing list softwares send either at a set interval OR when a certain number of messages are received - whichever happens first. Or when the digest gets bigger than N bytes. ___ 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] Achieving maximum performance when driving 5370A/B inputs
But YOU don't want to pay for those (OK if someone else is paying) - they are painfully expensive. D. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 28 February 2010 03:00 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Achieving maximum performance when driving 5370A/B inputs Actually there are miniature twinax style connectors, for example: http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E17F; http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E17F; Bruce ___ 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] DMTD Mixer Terminations
Hi All of the mixers I'm using are safe from any issues related to recent changes in the product. For the most part they are old enough to vote. Here's some more data from the original run: Peak to peak output voltage into a cap load (other loads are close): ZAD-3 .648 RPD-1 #12.48 RPD-1 #22.4 10514 #1.971 10514 #2.989 10534 .914 ZP3-MH 1.378 ZAD-1H 1.296 All are open circuit at audio. The data for the ZAD-3 is .644 V into a 50 ohm with blocking capacitor load. That's pretty close to what they show on page 4 of the app note. It would be lower with a 50 ohm full load, but they imply they are using 500 ohms. I believe the ZAD-3 is similar to the SAM-1 except for frequency range. At the eyeball level the waveform they show is the waveform I'm seeing with resistive termination. Their graph indicates an slightly asymetric response (check at 0 degrees) that I'm not seeing. The setup and circuit are deliberately pretty simple. Not a lot of stuff to go crazy. Any other data out there? Bob On Feb 28, 2010, at 10:58 PM, Bruce Griffiths wrote: Unless Minicircuits have made significant changes to the RPD-1 there has to be some kind of calibration error or an as yet poorly understood effect. Did you try the load and filter shown in the attached application note? Replicating Minicircuits measurements within 10% or so is probably necessary to correctly assess the effect of various termination networks. Bruce Bob Camp wrote: Hi Ok, RPD-1 #1 puts out 9.97 volts into a 500 ohm resistor to ground termination (no blocking capacitor). That's still well above the catalog spec. I'm running 25% more voltage than their 7 dbm. That still does not fully explain what I'm seeing. The scope does indeed indicate 15 volts when I hook it to a 15 volt supply. Given the number of broken pieces of test gear I seem to own that was worth checking. ... Bob On Feb 28, 2010, at 8:54 PM, Bob Camp wrote: Hi The Minicircuits guys claim 800 to 1000 mv / radian. In my units that would be 5 to 6.2 volts per cycle. I believe I'm getting ~ 3 X that mostly from the open circuit termination at audio. It's certainly something I could head back downstairs and check. The 10% increase in slope between resistive and capacitive termination has never really been enough with the RPD-1 to make it seem to be worth it. It's certainly worth it with a ZAD-3. Bob On Feb 28, 2010, at g8:39 PM, Bruce Griffiths wrote: The results for the RPD-1's are about what I expected: there's little difference in slope between either a 50 ohm +47nF termination or a 47nF termination. The slopes are about 6.5x greater than the values given by Minicircuits. (8mv/degree = 2.88V/cycle). I assume that they use 500 ohms connected directly to ground not via a capacitor. So there's something in NISTs claims of improved slope at least for the RPD-1. I suspect that NISTs original 50 ohm terminations were actually 50 ohms direct to ground not via a capacitor. Using a series capacitor increases the termination impedance at the beat frequency substantially over that when the resistor is connected directly to ground. Since its is also claimed by NIST and others that reactive termination reduces the noise, one also needs to measure the output noise spectral density for the various IF port terminations. Bruce Bob Camp wrote: Hi Here's some data: The setup is very simple: Two oscillators at 10 MHz driving common base / 50 ohm output buffers. The buffers ensure that the source impedance is really 50 ohms. One puts out 9.3 dbm the other 9.5 dbm. They can be tuned for a beat note in the 0 to 100 Hz range. The basic mixer termination filter is a pair cascaded / identical L networks. Both have 10 uh in the series leg and 0.047 uf to ground in the shunt leg. The audio end of the filter hooks straight into a digitizing scope. The termination options for the mixer are: 1) inductive - just running into the 10 uh of the first L network. 2) 50 ohms - drop a 57 ohm in series with 0.047 from the mixer output to ground 3) Capacitive - 0.047 uf to ground at the mixer output. The data is computed from the time to cross the center 50% of the output waveform. If the output is 1V p-p then the data would cover the range -.25 to +.25 volts. I've normalized it to volts / cycle. Divide by 2* pi if you want to get volts / radian. mixer 50 ohms inductive capacitive ZAD-3 3.512.969.98 RPD-1 #1 17.77 10.50 18.85 RPD-1 #2 17.40 10.058 18.53 10514A #1 5.796 4.396 10.31 10514A #2 5.826 4.406 10.33 10534A5.402
Re: [time-nuts] Achieving maximum performance when driving 5370A/B inputs
Hi That's been my experience in the past with unusual RF connectors. Unless they went into large scale production you can't afford them. Bob On Mar 1, 2010, at 7:44 AM, David C. Partridge wrote: But YOU don't want to pay for those (OK if someone else is paying) - they are painfully expensive. D. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 28 February 2010 03:00 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Achieving maximum performance when driving 5370A/B inputs Actually there are miniature twinax style connectors, for example: http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E17F; http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E17F; Bruce ___ 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] Achieving maximum performance when driving 5370A/Binputs
I have a collection of 6 Trompeter tri-axial (STP) adapters in a box which I got mixed in with an auction lot. If I'd had to buy them new they would have cost over $600: 150 Series Sub-Miniature Tri-Axial Range 3 off BN153 3-lug T-Adapters ($105 each) 2 off AD158 3-lug female-female barrel connector ($61 each) 70 Series Miniature Tri-Axial Range (BNC sized) 1 off TN2A 3-lug Paralleling Jack - two jacks, one plug ($86 each) I don't forsee myself using them, so if anyone needs them - give me a shout. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: 01 March 2010 12:52 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Achieving maximum performance when driving 5370A/Binputs Hi That's been my experience in the past with unusual RF connectors. Unless they went into large scale production you can't afford them. Bob On Mar 1, 2010, at 7:44 AM, David C. Partridge wrote: But YOU don't want to pay for those (OK if someone else is paying) - they are painfully expensive. D. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths Sent: 28 February 2010 03:00 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Achieving maximum performance when driving 5370A/B inputs Actually there are miniature twinax style connectors, for example: http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E17 F http://www.amphenolrf.com/products/twinbnc.asp?N=0sid=4B8860805409E1 7F Bruce ___ 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] Rock, gas, and air
On 1 Mar it was written: Rock I take to be crystal. How about gas and air? Which, improbably, brings us back to a thread of January 11th where JDB wrote: In protocol design, perfection has been reached not when there is nothing left to add, but when there is nothing left to take away. -- RFC 1925, Fundamental Truths of Networking which prompted Jerry S. to rejoin: The actual quote is: Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away. Antoine de Saint-Exupery French writer (1900 - 1944) The original quotation, from the book Terre des hommes, is: Il semble que la perfection soit atteinte non quand il n'y a plus rien à ajouter, mais quand il n'y a plus rien à retrancher. The English edition (ISBN 0-15-697090-2 page 46) of the book has the awkward: In anything at all, perfection is finally attained not when there is no longer anything to add but when there is no longer anything to take away, when a body has been stripped down to its nakedness. And the English edition is entitled Wind, Sand and Stars ... not quite rock, gas and air, but close '-% [If anybody wants mine (f.o.c), drop me your address]. -- == James R Miller Cambridge, England == ___ 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] Rock, gas, and air
Hi Are we now to the point where the use of wind direction change in Sweden as a primary time standard is actually in question? Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of James R Miller Sent: Monday, March 01, 2010 10:13 AM To: time-nuts@febo.com Subject: Re: [time-nuts] Rock, gas, and air On 1 Mar it was written: Rock I take to be crystal. How about gas and air? Which, improbably, brings us back to a thread of January 11th where JDB wrote: In protocol design, perfection has been reached not when there is nothing left to add, but when there is nothing left to take away. -- RFC 1925, Fundamental Truths of Networking which prompted Jerry S. to rejoin: The actual quote is: Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away. Antoine de Saint-Exupery French writer (1900 - 1944) The original quotation, from the book Terre des hommes, is: Il semble que la perfection soit atteinte non quand il n'y a plus rien à ajouter, mais quand il n'y a plus rien à retrancher. The English edition (ISBN 0-15-697090-2 page 46) of the book has the awkward: In anything at all, perfection is finally attained not when there is no longer anything to add but when there is no longer anything to take away, when a body has been stripped down to its nakedness. And the English edition is entitled Wind, Sand and Stars ... not quite rock, gas and air, but close '-% [If anybody wants mine (f.o.c), drop me your address]. -- == James R Miller Cambridge, England == ___ 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] Loran-C (?) antennna in low sun
I stumbled over this picture from Jan Mayen: http://www.jan-mayen.no/nyhet/2010/01_januar/januar/crossfox1b.jpg I'm not entirely sure if it is their Loran-C transmission antenna, but it is a damn good picture whatever the antenna does... Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Loran-C (?) antennna in low sun
This is an HF Vertical Monopole. Is a TCI 550 Single Tower Inverted Cone Antenna Steve KD2OM -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Monday, March 01, 2010 2:33 PM To: time-nuts@febo.com Subject: [time-nuts] Loran-C (?) antennna in low sun I stumbled over this picture from Jan Mayen: http://www.jan-mayen.no/nyhet/2010/01_januar/januar/crossfox1b.jpg I'm not entirely sure if it is their Loran-C transmission antenna, but it is a damn good picture whatever the antenna does... Poul-Henning -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rack-mounting an LPRO?
Hi everyone, First of all, thank you all very much for the many reactions to my query. I'd like to clarify a few things (my original posting was a bit too terse, I guess). The LPRO-101 is 1.5 high, 3.7 deep and 5.0 wide. Its height makes it ideal to fit inside a 1U rack unit while laying on its baseplate, and the manual states it was designed to fit in 1U or 3U VME units. And I happen to have a 1U 19 rack enclosure that fits it very nicely, snug between the top and bottom cover. LPRO stands for 'Low Profile Rubidium Oscillator. But from many of your reactions, it seems that this proposed setup would lead to problems getting rid of the heat generated by the LPRO, and the enclosure's baseplate would not be sufficient for cooling. I particularly liked the heat-pipe solution that was suggested, but there would be not enough height in the 1U enclosure for such a system. There seem to exist heatpipes of only 500um thickness these days, but I have no idea where one could find one of those. Scott Mace replied that he has a 1U high Datum Rubidium unit, probably something like their Datum-8040 product, and it works fine for him. As I already have the LPRO, rack-unit and PSU, I will attempt to get this combination to work, but will clearly have to put much more effort into (passively) cooling things than anticipated. Thanks again for the input, and I'll let you know how things turn out in a few weeks. Regards, Paul Boven - 73 de PEaNUT ___ 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] Rack-mounting an LPRO?
Hi There is another unit with the same name (also an LPRO) that is 1.25 high rather than 1.5. That unit is a bit better for a 1U rack. Bob On Mar 1, 2010, at 6:09 PM, Paul Boven wrote: Hi everyone, First of all, thank you all very much for the many reactions to my query. I'd like to clarify a few things (my original posting was a bit too terse, I guess). The LPRO-101 is 1.5 high, 3.7 deep and 5.0 wide. Its height makes it ideal to fit inside a 1U rack unit while laying on its baseplate, and the manual states it was designed to fit in 1U or 3U VME units. And I happen to have a 1U 19 rack enclosure that fits it very nicely, snug between the top and bottom cover. LPRO stands for 'Low Profile Rubidium Oscillator. But from many of your reactions, it seems that this proposed setup would lead to problems getting rid of the heat generated by the LPRO, and the enclosure's baseplate would not be sufficient for cooling. I particularly liked the heat-pipe solution that was suggested, but there would be not enough height in the 1U enclosure for such a system. There seem to exist heatpipes of only 500um thickness these days, but I have no idea where one could find one of those. Scott Mace replied that he has a 1U high Datum Rubidium unit, probably something like their Datum-8040 product, and it works fine for him. As I already have the LPRO, rack-unit and PSU, I will attempt to get this combination to work, but will clearly have to put much more effort into (passively) cooling things than anticipated. Thanks again for the input, and I'll let you know how things turn out in a few weeks. Regards, Paul Boven - 73 de PEaNUT ___ 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] My DIY frequency counter and a request for help
Gerard PG5G wrote: I have had a few replies, both on list and off list, including some offers for help and some suggestions regarding the capabilities of my counter. Thanks to everyone who took the time to write. I understand from various replies I had that I cannot measure ADEV the way I thought I could. I am an electronics man, not a mathematician (or should that be mathemagician?). Adding the ADEV was an afterthought and I'll leave the development of that for now. Magnus sent me the most detailed list of questions and suggestions. I think that by answering his post I cover most of what others have asked me as well. Regards Gerard Magnus Danielson wrote: Would you consider to disclose your architecture somewhat more? In broad terms: Input conditioning with ADCMP600 comparators followed by FF divide by 2 to get a 50% duty cycle signal on both the ref and input channel. PIC micro as time base generates 0.2 ms start pulses, cleaned up with a FF. Output of this FF is start signal to the TDC. Synchronisation with the input signal using a few more FFs, generating a switch signal on the next rising edge. This switch signal is used to switch between counter A and B (two more PICs) and is the stop signal to the TDC. I also have the inverse of the input signal available. By switching on the normal signal and counting the inverse signal I can make sure I never get the wrong count in a measurement period (hence the need for 50% duty cycle). A fourth PIC communicates with the TDC and controls the communication channel via an FTDI USB interface chip. Internally the counter works with a normal serial protocol at 1MB, on the PC side it uses FTDI's D2XX driver to process data in burst mode as opposed to RS232 mode. Each time stamp consists of 10 Bytes. 2 for synchronisation, 4 for the count, 4 for the time stamp expressed as a multiple of the TDC clock period of 200ns (5 MHz). The TDC is an ACAM TDC-GP2. After each measurement it performs a calibration to the ref clock provided (5 MHz) and gives an output as a 32 bit fixed point number with 16 integer bits and 16 fractional bits. So, apart form the TDC these are all cheap off the shelf components available from any electronics distributor. Many thanks, now we know better what we are referring to. Could you output time and event values from the time-stamping? Would allow us to do some off-line processing independently. I'll work on that. I need to get some data logging functions build into the software anyway. Give me a few days. Fair enough. It is always good to be able to drop a log-file and process and analyze off-line either with ones own tools, off the shelf or toss something together. Incremental form of ADEV/TDEV estimators would be nice for the real-time variant tool. Could you try different frequencies/amplitudes (would be good for establishing the slew-rate dependency, i.e. internal noise). Measure period jitter and plot for different slew-rates (frequency and amplitude), use shortest tau possible. Will do. I am bit limited in what I can generate at the moment. That screen shot was the output of a HP8922H used as a signal generator set to 10.00 MHz. I guess there must be time nuts on here who recognised the frequency of 10 000 000.461 Hz. If I select 11 MHz I get 11 000 000.461 Hz. At 100 MHz I get 100 000 000.461 Hz. Must be the way the synthesiser works internally. (BTW, this matches what I get on my 5384A counter). I'll have to get the data logging sorted before I can take this much further. Sounds like a systematic offset. However, that can be useful for you. Slowly scans the interpolator bins. Could you hook up the reference clock with different lengths of coax cables. This would assist in measure the background noise and the different lengths of cables would allow some indication of interpolator non-linearity and input cross-talk. Will do. I have now written some software which calculates the standard deviation of the time stamps. That is indeed what you want to assist you. If I connect the ref frequency twice than ideally this should be zero. In reality it shows the noise of the whole set up. I have noticed already that by disconnecting and reconnecting the input side I can get my counter to work in two different 'modes' with regards to the calculated standard deviation of the time stamps. My guess at the moment is that this depends on whether the two input dividers are in or out of synch but I need to do some more testing. You could use a separate DFF to clock the state from one of the outputs with the other... and just hook a LED to it. That would help you to visualize the modes in the case that it is true in-/out-of-phase mode of the input dividers. I would assume that you are experiencing the cross-talk that I was referring to. Cross-talk could either be seen as capacitive coupling between channels or common-inductance of two stages. Channel-to-channel
Re: [time-nuts] Rock, gas, and air
On Tue, Mar 2, 2010 at 01:17, Bob Camp li...@rtty.us wrote: Hi Are we now to the point where the use of wind direction change in Sweden as a primary time standard is actually in question? Sweden has been a neutral country for some time, that should help. Un-biased readings, and all that. -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ 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] The day just got shorter
Apparently the earthquake in Chile has shifted he earth's axis enough to shorten the day by 1.26 microseconds. Darn, I now have to readjust my Accutron watch. _ Hotmail: Powerful Free email with security by Microsoft. http://clk.atdmt.com/GBL/go/201469230/direct/01/ ___ 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] Vremya-ch Hydrogen Masers
Anyone here have any experience with these masers? In particular the VCH-1005A? I have been tasked to look after a number of these units and am currently going through the manuals (which are in English but written by a Russian, so they can be challenging :-) Any thoughts, hints or tips would be good, but it would also be handy to have contacts for down the track. These are newly installed. Regards, Jim Palfreyman ___ 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] The day just got shorter
Hi I suspect they are adjusting the Swedish winds as we type Bob On Mar 1, 2010, at 9:08 PM, Mark Sims wrote: Apparently the earthquake in Chile has shifted he earth's axis enough to shorten the day by 1.26 microseconds. Darn, I now have to readjust my Accutron watch. _ Hotmail: Powerful Free email with security by Microsoft. http://clk.atdmt.com/GBL/go/201469230/direct/01/ ___ 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] Vremya-ch Hydrogen Masers
Hi A couple of our guys did a plant visit back in the late 90's. They had a prototype of your masers running at that time. Their stories were fairly interesting. I suspect things have improved since that time Bob On Mar 1, 2010, at 9:11 PM, Jim Palfreyman wrote: Anyone here have any experience with these masers? In particular the VCH-1005A? I have been tasked to look after a number of these units and am currently going through the manuals (which are in English but written by a Russian, so they can be challenging :-) Any thoughts, hints or tips would be good, but it would also be handy to have contacts for down the track. These are newly installed. Regards, Jim Palfreyman ___ 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] Vremya-ch Hydrogen Masers
Perhaps obviously, Vremya is Russian for time. -Pete On Mar 1, 2010, at 6:11 PM, Jim Palfreyman wrote: Anyone here have any experience with these masers? In particular the VCH-1005A? I have been tasked to look after a number of these units and am currently going through the manuals (which are in English but written by a Russian, so they can be challenging :-) Any thoughts, hints or tips would be good, but it would also be handy to have contacts for down the track. These are newly installed. Regards, Jim Palfreyman ___ 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] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?
Interesting that the effect could be this large. http://www.smh.com.au/technology/sci-tech/chilean-quake-shifted-earths-axis-nasa-scientist-20100302-peqe.html?autostart=1 ___ 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] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?
How would one go about verifying this? The angular difference after 1 year is about 3E-8 radians, which is probably well beyond the absolute pointing accuracy of any telescope, and swamped by lunar tidal deceleration anyway. Henry On Mon, Mar 1, 2010 at 7:36 PM, mc0fred mc0f...@gmail.com wrote: Interesting that the effect could be this large. http://www.smh.com.au/technology/sci-tech/chilean-quake-shifted-earths-axis-nasa-scientist-20100302-peqe.html?autostart=1 ___ 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. -- Henry Hallam Sent from my Laptop ___ 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] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?
3E-8 radians is 0.03 microradians. A microradian is about 5 arc-seconds, so about 0.15 arc-seconds per year. I think that's in the range that could be observed either optically or by VLBI. -John = How would one go about verifying this? The angular difference after 1 year is about 3E-8 radians, which is probably well beyond the absolute pointing accuracy of any telescope, and swamped by lunar tidal deceleration anyway. Henry On Mon, Mar 1, 2010 at 7:36 PM, mc0fred mc0f...@gmail.com wrote: Interesting that the effect could be this large. http://www.smh.com.au/technology/sci-tech/chilean-quake-shifted-earths-axis-nasa-scientist-20100302-peqe.html?autostart=1 ___ 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] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?
Pretty trivial to do with GPS where a 1 ns error is under 1 foot of position error (and a geodetic grade GPS can give sub-millimeter accuracy)... even a cheap consumer grade unit is under 10 feet of error. 1.26 us of orbital change is over 1100 feet of error. One trick is to compare the pre-earthquake GPS almanac/ephemeris data with the post earthquake data. I suspect that a lot of geodetic monitoring stations are scrambling to keep up with what the earth is currently doing. --- How would one go about verifying this? The angular difference after 1 year is about 3E-8 radians, which is probably well beyond the absolute pointing accuracy of any telescope, and swamped by lunar tidal deceleration anyway. _ Hotmail: Free, trusted and rich email service. http://clk.atdmt.com/GBL/go/201469228/direct/01/ ___ 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] Chilean quake shifted Earth's axis. The length of the day shorter by 1.26 microseconds ?
Of course... I am designing a GPS receiver as my day job and didn't think of that ;) Henry On Mon, Mar 1, 2010 at 8:36 PM, Mark Sims hol...@hotmail.com wrote: Pretty trivial to do with GPS where a 1 ns error is under 1 foot of position error (and a geodetic grade GPS can give sub-millimeter accuracy)... even a cheap consumer grade unit is under 10 feet of error. 1.26 us of orbital change is over 1100 feet of error. One trick is to compare the pre-earthquake GPS almanac/ephemeris data with the post earthquake data. I suspect that a lot of geodetic monitoring stations are scrambling to keep up with what the earth is currently doing. --- How would one go about verifying this? The angular difference after 1 year is about 3E-8 radians, which is probably well beyond the absolute pointing accuracy of any telescope, and swamped by lunar tidal deceleration anyway. _ Hotmail: Free, trusted and rich email service. http://clk.atdmt.com/GBL/go/201469228/direct/01/ ___ 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. -- Henry Hallam Sent from my Laptop ___ 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.
