Re: [time-nuts] Cable length calibration
If the nominal velocity of propagation is known and length is known delay is easily determined mathematically Time Domain Reflectrometry is the usual technique for finding cable length but even there the cables NVP is an essential parameter if you want to compute length but not essential in time nuts application because we are interested in delay which a TDR reads directly When using a TDR its best if cable is unterminated as the discontinuity at the end is helpful as a marker. Also most TDRs like the Tek 1502 can put 100v or more on the cable which will blow most GPS antennas > On Jun 29, 2016, at 4:08 PM, Brooke Clarke wrote: > > Hi Hal: > > I think the cal process is essentially a time domain reflection measure of > cable length. The GPS receiver and the cable cal hardware would be in the > antenna unit. > The 1 PPS signal would be aligned at the output of the cable. > > -- > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/2012Issues.html > The lesser of evils is still evil. > > Original Message >> bro...@pacific.net said: >>> At one point they were looking into making a GPS time receiver where the >>> cable length calibration would be built-in. >> How would you do that? >> >> The obvious way is to compare the time you get with a known-good time, but if >> you had that, why would you want this new GPS with an unknown cable length. >> >> You might be able to do it by measuring the DC drop. Getting enough accuracy >> seems tough. > > ___ > 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] HP 5071A second life
I have an old HP 5071 Cs-standard here on my desk. The oven of the (second) tube has lost its Cs completely so the instrument is no longer working. Since the electronic is quite old we acquired a complete new 5071A (now from Symmetricom). I tried to "reactivate" the HP as a fancy desktop clock without success. Tried different commands on the serial bus but was not able to switch off the fatal error states (which is ok for the proper use). It is not possible to set Time and Date, nor perform a synchronisation. The display just stays dark. Also the reference oscillator is driven to one end causing a horrible frequency stability. Does somebody know a procedure to override the error states so that the display works with a depleted CBT by programming? I do not want to modify the hardware. And to state it explicitly: I do not need a actual time/frequency standard just a mockup for my desk. Michael Dr. Michael Matus - BEV - Bundesamt fuer Eich- und Vermessungswesen Leiter des Referates Dimensionelle Groessen, Frequenz, Zeit (Head of Section, Dimensional Quantities, Frequency, Time) Tel. +43 1 21110-6540, Fax +43 1 21110-996000 1160 Wien, Arltgasse 35, Austria michael.ma...@bev.gv.at www.bev.gv.at - ___ 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] MSF 60 kHz off the air during the day for annual maintenance: 4 – 20 July 2016
MSF 60 kHz off the air during the day for annual maintenance: 4 – 20 July 2016 See: http://www.npl.co.uk/science-technology/time-frequency/products-and-services/time/msf-outages Cheers, David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ 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 5071A second life
>From the front panel: Top -> Clock -> Set -> Display:ON The same menu page also allows you to set the HH:MM:SS time. This can be done within a few seconds of power up, regardless if the CBT is warming up, dead, or alive. The amber attention LED will remain lit, but a dead CBT should not affect the red LED time display. /tvb - Original Message - From: "Matus Michael" To: Sent: Thursday, June 30, 2016 5:51 AM Subject: [time-nuts] HP 5071A second life >I have an old HP 5071 Cs-standard here on my desk. The oven of the (second) >tube has lost its Cs completely so the instrument is no longer working. Since >the electronic is quite old we acquired a complete new 5071A (now from >Symmetricom). > > I tried to "reactivate" the HP as a fancy desktop clock without success. > Tried different commands on the serial bus but was not able to switch off the > fatal error states (which is ok for the proper use). It is not possible to > set Time and Date, nor perform a synchronisation. The display just stays > dark. Also the reference oscillator is driven to one end causing a horrible > frequency stability. > > Does somebody know a procedure to override the error states so that the > display works with a depleted CBT by programming? I do not want to modify the > hardware. And to state it explicitly: I do not need a actual time/frequency > standard just a mockup for my desk. > > Michael > > Dr. Michael Matus > - > BEV - Bundesamt fuer Eich- und Vermessungswesen > Leiter des Referates Dimensionelle Groessen, Frequenz, Zeit > (Head of Section, Dimensional Quantities, Frequency, Time) > Tel. +43 1 21110-6540, Fax +43 1 21110-996000 > 1160 Wien, Arltgasse 35, Austria > michael.ma...@bev.gv.at > www.bev.gv.at > - > ___ > 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] buying a time interval counter
Hi, I've ordered a SR620 with the option 01 (higher stability standard) Should be there in August Thanks Stephane -- Message d'origine -- De : "Brooke Clarke" À : "Stéphane Rey" ; "Discussion of precise time and frequency measurement" Envoyé 29/06/2016 19:20:22 Objet : Re: [time-nuts] buying a time interval counter Hi Stephane: I traded my HP 53132A counter for an SR 620. The 53132 has what I'd call a user hostile interface, so if you are manually controlling the counter the SR 620 has a huge advantage. I also like the long display on the 620 which can be read from across the room. PS Stanford Research is a company founded by physicists and makes some really high quality stuff. In fact some of the products HP/Agilent/Keysight sells are repackaged SR instruments. http://www.prc68.com/I/TandFTE.shtml#SR620 The claim to fame for the HP 53132A is that it can make a frequency (not time interval) measurement to 1E12 in a second. Here's how to get that same result with the SR620: http://www.prc68.com/I/FTS4060.shtml#SR620Fast On the down side the printing functions on the 620 require an Epsom printer. Does anyone have a solution for that? PS SR also makes a 10 MHz crystal oscillator that has options trading stability for aging as well as the EFC tuning polarity and range so as to match other OCXOs. http://prc68.com/I/TandFTE.shtml#SC10 At one point they were looking into making a GPS time receiver where the cable length calibration would be built-in. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message Hello there, I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. What model still distributed would you think is good for that at the moment ? Thanks & cheers Stephane ___ 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] HP 5071A second life
Michael Thats going to be quite the clock. Very unfortunate but thats what happens the Cs dry up. I seriously messed with a much older CS and was able to get a few more C's out of the tube. The 5071 is smart so not sure any of what I did makes any sense. Basically heating the oven to a slightly higher temperature. The other point that may not be of interest is that even dead 5071s seem to have a great deal of value. Regards Paul WB8TSL On Thu, Jun 30, 2016 at 8:51 AM, Matus Michael wrote: > I have an old HP 5071 Cs-standard here on my desk. The oven of the > (second) tube has lost its Cs completely so the instrument is no longer > working. Since the electronic is quite old we acquired a complete new 5071A > (now from Symmetricom). > > I tried to "reactivate" the HP as a fancy desktop clock without success. > Tried different commands on the serial bus but was not able to switch off > the fatal error states (which is ok for the proper use). It is not possible > to set Time and Date, nor perform a synchronisation. The display just stays > dark. Also the reference oscillator is driven to one end causing a horrible > frequency stability. > > Does somebody know a procedure to override the error states so that the > display works with a depleted CBT by programming? I do not want to modify > the hardware. And to state it explicitly: I do not need a actual > time/frequency standard just a mockup for my desk. > > Michael > > Dr. Michael Matus > - > BEV - Bundesamt fuer Eich- und Vermessungswesen > Leiter des Referates Dimensionelle Groessen, Frequenz, Zeit > (Head of Section, Dimensional Quantities, Frequency, Time) > Tel. +43 1 21110-6540, Fax +43 1 21110-996000 > 1160 Wien, Arltgasse 35, Austria > michael.ma...@bev.gv.at > www.bev.gv.at > - > ___ > 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] Cable length calibration
The Tektronix 1502 uses a tunnel diode pulser to produce a 50 picosecond output step of about 200 millivolts. There is a misprint in the theory section of the service manual which says "400 V" instead of "400mV". On Thu, 30 Jun 2016 04:19:43 -0400, you wrote: >If the nominal velocity of propagation is known and length is known delay is >easily determined mathematically > >Time Domain Reflectrometry is the usual technique for finding cable length but >even there the cables NVP is an essential parameter if you want to compute >length but not essential in time nuts application because we are interested in >delay which a TDR reads directly When using a TDR its best if cable is >unterminated as the discontinuity at the end is helpful as a marker. Also >most TDRs like the Tek 1502 can put 100v or more on the cable which will blow >most GPS antennas ___ 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] Information request
I have been given a 10MHz oscillator that appears to be in good physical condition but I have no further information on it hence this request. It is marked as follows:-Quartzkeramic 2006/10SCD-531 10.000MHz 12v= K 837383 Any information such as connection details, performance etc. will be greatly appreciated. Regards Peter ___ 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] buying a time interval counter
How does the Fluke PM6690 (same as Pendulum CNT-90) compare to the SR620? A neighbor is selling one in perfect condition (per him) for $900 Jerry NY2KW -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Stéphane Rey Sent: Thursday, June 30, 2016 10:07 AM To: Brooke Clarke; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] buying a time interval counter Hi, I've ordered a SR620 with the option 01 (higher stability standard) Should be there in August Thanks Stephane -- Message d'origine -- De : "Brooke Clarke" À : "Stéphane Rey" ; "Discussion of precise time and frequency measurement" Envoyé 29/06/2016 19:20:22 Objet : Re: [time-nuts] buying a time interval counter >Hi Stephane: > >I traded my HP 53132A counter for an SR 620. The 53132 has what I'd >call a user hostile interface, so if you are manually controlling the >counter the SR 620 has a huge advantage. >I also like the long display on the 620 which can be read from across >the room. > >PS Stanford Research is a company founded by physicists and makes some >really high quality stuff. In fact some of the products >HP/Agilent/Keysight sells are repackaged SR instruments. >http://www.prc68.com/I/TandFTE.shtml#SR620 > >The claim to fame for the HP 53132A is that it can make a frequency >(not time interval) measurement to 1E12 in a second. Here's how to get >that same result with the SR620: >http://www.prc68.com/I/FTS4060.shtml#SR620Fast > >On the down side the printing functions on the 620 require an Epsom >printer. Does anyone have a solution for that? > >PS SR also makes a 10 MHz crystal oscillator that has options trading >stability for aging as well as the EFC tuning polarity and range so as >to match other OCXOs. >http://prc68.com/I/TandFTE.shtml#SC10 > >At one point they were looking into making a GPS time receiver where >the cable length calibration would be built-in. > >-- Have Fun, > >Brooke Clarke >http://www.PRC68.com >http://www.end2partygovernment.com/2012Issues.html >The lesser of evils is still evil. > > Original Message >>Hello there, >> >>I'm planning to buy a such instrument in order to do some frequency >>stability measurement at work. The SR620 seems to be discontinued. >>What model still distributed would you think is good for that at the >>moment ? >> >>Thanks & cheers >>Stephane >>___ >>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] buying a time interval counter
Ji Jerry, The Fluke exhibit a 100ps resolution whereas the SR620 has 25ps. This is the main difference I see from datasheets. cheers Stephane -- Message d'origine -- De : "Jerry" À : "'Stéphane Rey'" ; "'Discussion of precise time and frequency measurement'" ; "'Brooke Clarke'" Envoyé 30/06/2016 17:01:50 Objet : RE: [time-nuts] buying a time interval counter How does the Fluke PM6690 (same as Pendulum CNT-90) compare to the SR620? A neighbor is selling one in perfect condition (per him) for $900 Jerry NY2KW -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Stéphane Rey Sent: Thursday, June 30, 2016 10:07 AM To: Brooke Clarke; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] buying a time interval counter Hi, I've ordered a SR620 with the option 01 (higher stability standard) Should be there in August Thanks Stephane -- Message d'origine -- De : "Brooke Clarke" À : "Stéphane Rey" ; "Discussion of precise time and frequency measurement" Envoyé 29/06/2016 19:20:22 Objet : Re: [time-nuts] buying a time interval counter Hi Stephane: I traded my HP 53132A counter for an SR 620. The 53132 has what I'd call a user hostile interface, so if you are manually controlling the counter the SR 620 has a huge advantage. I also like the long display on the 620 which can be read from across the room. PS Stanford Research is a company founded by physicists and makes some really high quality stuff. In fact some of the products HP/Agilent/Keysight sells are repackaged SR instruments. http://www.prc68.com/I/TandFTE.shtml#SR620 The claim to fame for the HP 53132A is that it can make a frequency (not time interval) measurement to 1E12 in a second. Here's how to get that same result with the SR620: http://www.prc68.com/I/FTS4060.shtml#SR620Fast On the down side the printing functions on the 620 require an Epsom printer. Does anyone have a solution for that? PS SR also makes a 10 MHz crystal oscillator that has options trading stability for aging as well as the EFC tuning polarity and range so as to match other OCXOs. http://prc68.com/I/TandFTE.shtml#SC10 At one point they were looking into making a GPS time receiver where the cable length calibration would be built-in. -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html The lesser of evils is still evil. Original Message Hello there, I'm planning to buy a such instrument in order to do some frequency stability measurement at work. The SR620 seems to be discontinued. What model still distributed would you think is good for that at the moment ? Thanks & cheers Stephane ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] The Nature of Noise
With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator? Bob - AE6RV --- GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info ___ 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 Nature of Noise
Bob, I am about to get myself into a lot of trouble. If the noise is coherent in some way then its not really noise anymore its a signal or its filtered in some way as compared to C. There you go I feel the hot emails on the way already. Should be a good read. Regards Paul WB8TSL On Thu, Jun 30, 2016 at 2:30 PM, Bob Stewart wrote: > With my recent Cs problems, I've been wondering about the subject of noise > generation and measurement. Specifically, my question is this: Let's say > that I have 3 disciplined oscillators: A, B, and C. So, I use the same > 5370 to create a 1000 second ADEV and discover that the 1s noise value > between A and B is low, while the 1s noise between A and C, as well as B > and C is high. Can I then say that both A and B are low noise devices? Or > is it possible that even though I'm measuring 1000 points, both A and B are > high noise devices, but somehow are noisy in the same exact way, and it's > actually C that's the low noise oscillator? > > Bob - > AE6RV > --- > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > ___ > 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] The Nature of Noise
On Thu, 30 Jun 2016 18:30:35 + (UTC) Bob Stewart wrote: > With my recent Cs problems, I've been wondering about the subject of noise > generation and measurement. Specifically, my question is this: Let's say > that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 > to create a 1000 second ADEV and discover that the 1s noise value between A > and B is low, while the 1s noise between A and C, as well as B and C is > high. Can I then say that both A and B are low noise devices? Or is it > possible that even though I'm measuring 1000 points, both A and B are high > noise devices, but somehow are noisy in the same exact way, and it's > actually C that's the low noise oscillator? Short answer: yes Long answer: Yes, but unlikely :-) You can see the output of the oscillators as random processes and model them as such (MIT opencoursware has some good lectures on that topic). If the processes are all independent, then you can assume that A and B will have the lowest noise and estimate the ADEV values of C and the second nosiest oscillator with good confidence, and of the lowest noise oscillator with some confidence (keyword: "three cornered hat"). In reality you will never have totally independent oscillators, there will be always some coupling through power supplies (even mains power) or through RF coupling. Heck, even your measurement instrument might couple the oscillators if you are not very carefull. So it really might be that A and B are just bad oscillators, that injection locked to each other, and thus seemed more stable/less noisy than A+C and B+C. But generally, high stability/low noise oscillators are usually made such, that the output and the power supply are decoupled from the oscillator itself as much as possible, to make the effect of coupling (which is always present) so small that it get swamped out by all other noise sources. Attila Kinali -- Malek's Law: Any simple idea will be worded in the most complicated way. ___ 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] Cable length calibration
On 30 June 2016 at 09:19, Scott McGrath wrote: > If the nominal velocity of propagation is known and length is known delay > is easily determined mathematically > Except that coax does not have a uniform impedance or velocity factor. Both will vary as a function of position and frequency. How relevant this is depends on the accuracy you require, but since it is time-nuts, it is reasonable to assume that such a simplistic method is not of the standard expected on time-nuts. Dave ___ 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] Cable length calibration
Scott wrote: When using a TDR its best if cable is unterminated as the discontinuity at the end is helpful as a marker. Someone else previously asked how you're expected to do TDR on a GPS antenna cable since everything is matched (therefore, presumably, no reflections). There are ALWAYS reflections. As one message in this thread noted, TDR easily shows sharp bends in coax. Plus, a GPS antenna will be "matched" only at a relatively narrow band of frequencies centered on the frequency(ies) it receives (L1, L1+L2, etc.). Also note that GPS antennas specified as having 50 ohm outputs are often (if not usually) used with 75 ohm cable. (Trimble actually advises this.) You can do the TDR situationally (when the receiver is powered up, and whenever an antenna fault is cleared), or repetitively during operation (e.g., once a minute). I see no reason why either strategy would not work well on a GPS antenna cable. There is no need to use signals that would damage a GPS antenna preamp. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] The Nature of Noise
Hi If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is possible that you are getting bad information. This is a classic argument about comparing devices from the same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient. Bob > On Jun 30, 2016, at 2:30 PM, Bob Stewart wrote: > > With my recent Cs problems, I've been wondering about the subject of noise > generation and measurement. Specifically, my question is this: Let's say > that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 > to create a 1000 second ADEV and discover that the 1s noise value between A > and B is low, while the 1s noise between A and C, as well as B and C is high. > Can I then say that both A and B are low noise devices? Or is it possible > that even though I'm measuring 1000 points, both A and B are high noise > devices, but somehow are noisy in the same exact way, and it's actually C > that's the low noise oscillator? > > Bob - AE6RV > --- > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > ___ > 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] Cable length calibration
As a practical matter, in the lab we seldom need a cable delay measured to better than +/- 0.5 ns, which we usually do as a time interval measurement, with a 1 pps into a tee on channel A of a TIC and then the cable from the tee to channel B. For cables up to 40 m or so, just measuring the physical length is as accurate (experimentally determined!). A while back, EURAMET ran a pilot where a few lengths of cable were circulated amongst a number of NMIs who then had to measure the delays. The reported scatter was about +/- 1 ns, as I recall. This mainly came down to differences in test signals, trigger levels etc. Cheers Michael On Fri, Jul 1, 2016 at 7:03 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote: > On 30 June 2016 at 09:19, Scott McGrath wrote: > >> If the nominal velocity of propagation is known and length is known delay >> is easily determined mathematically >> > > Except that coax does not have a uniform impedance or velocity factor. Both > will vary as a function of position and frequency. How relevant this is > depends on the accuracy you require, but since it is time-nuts, it is > reasonable to assume that such a simplistic method is not of the standard > expected on time-nuts. > > Dave > ___ > 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] Cable length calibration
I'd say it depends on the Time Nut 😀. NVP X Distance will get you close and for a beginning time nut is a worthwhile exercise To improve delay calculations now you need instrumentation that not all especially beginning time nuts own.I've got a 20 Ghz Agilent scope/TDR along with a 110 Ghz network analyzer and just putting a cable on the network analyzer and handling it you can see the characteristics changeSo yes you are correct that the simple NVPxDistance is not suitable for advanced time nuttery. In fact the delay will change with temperature and barometric pressure unless you are using hardline and that's subject to humidity unless filled with dry nitrogen under pressure. Content by Scott Typos by Siri > On Jun 30, 2016, at 5:03 PM, Dr. David Kirkby (Kirkby Microwave Ltd) > wrote: > >> On 30 June 2016 at 09:19, Scott McGrath wrote: >> >> If the nominal velocity of propagation is known and length is known delay >> is easily determined mathematically > > Except that coax does not have a uniform impedance or velocity factor. Both > will vary as a function of position and frequency. How relevant this is > depends on the accuracy you require, but since it is time-nuts, it is > reasonable to assume that such a simplistic method is not of the standard > expected on time-nuts. > > Dave > ___ > 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] Cable length calibration
This is highly dependent on the TDR especially ones designed for long twisted pair runs where a high voltage pulse is used to overcome resistive losses Content by Scott Typos by Siri > On Jun 30, 2016, at 10:59 AM, David wrote: > > The Tektronix 1502 uses a tunnel diode pulser to produce a 50 > picosecond output step of about 200 millivolts. There is a misprint > in the theory section of the service manual which says "400 V" instead > of "400mV". > >> On Thu, 30 Jun 2016 04:19:43 -0400, you wrote: >> >> If the nominal velocity of propagation is known and length is known delay is >> easily determined mathematically >> >> Time Domain Reflectrometry is the usual technique for finding cable length >> but even there the cables NVP is an essential parameter if you want to >> compute length but not essential in time nuts application because we are >> interested in delay which a TDR reads directly When using a TDR its best if >> cable is unterminated as the discontinuity at the end is helpful as a >> marker. Also most TDRs like the Tek 1502 can put 100v or more on the cable >> which will blow most GPS antennas > ___ > 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] Cable length calibration
We are all time nuts, so there's an obvious answer: What you do, is raise the GPS up to a height the same as the cable length. You then drop it, measure the time until it hits the ground, and use d = 0.5 a * t * t to calculate d. Then you correct for the velocity factor. Tim N3QE On Wed, Jun 29, 2016 at 3:28 PM, Hal Murray wrote: > > bro...@pacific.net said: > > At one point they were looking into making a GPS time receiver where the > > cable length calibration would be built-in. > > How would you do that? > > The obvious way is to compare the time you get with a known-good time, but > if > you had that, why would you want this new GPS with an unknown cable length. > > You might be able to do it by measuring the DC drop. Getting enough > accuracy > seems tough. > > > -- > These are my opinions. I hate spam. > > > > ___ > 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] The Nature of Noise
Thanks Bob and Attila, This problem with the Cs kind of brought the whole question of noise and what ADEVs mean into focus for me. Like most newbies, I had read about the ever increasing stability of time standards and wondered how they could actually know that they were better. I've seen the term 3-cornered hat bandied about, but I didn't really grock it until now. Bob --- GFS GPSDO list: groups.yahoo.com/neo/groups/GFS-GPSDOs/info From: Bob Camp To: Bob Stewart ; Discussion of precise time and frequency measurement Sent: Thursday, June 30, 2016 4:27 PM Subject: Re: [time-nuts] The Nature of Noise Hi If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is possible that you are getting bad information. This is a classic argument about comparing devices from the same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient. Bob > On Jun 30, 2016, at 2:30 PM, Bob Stewart wrote: > > With my recent Cs problems, I've been wondering about the subject of noise > generation and measurement. Specifically, my question is this: Let's say > that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 > to create a 1000 second ADEV and discover that the 1s noise value between A > and B is low, while the 1s noise between A and C, as well as B and C is high. > Can I then say that both A and B are low noise devices? Or is it possible > that even though I'm measuring 1000 points, both A and B are high noise > devices, but somehow are noisy in the same exact way, and it's actually C > that's the low noise oscillator? > > Bob - AE6RV > --- > GFS GPSDO list: > groups.yahoo.com/neo/groups/GFS-GPSDOs/info > ___ > 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] Cable length calibration
On 6/30/16 5:52 PM, Tim Shoppa wrote: We are all time nuts, so there's an obvious answer: What you do, is raise the GPS up to a height the same as the cable length. You then drop it, measure the time until it hits the ground, and use d = 0.5 a * t * t to calculate d. Then you correct for the velocity factor. or rig it as a pendulum, and correct for the gravitational pull of the moon and sun ___ 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] Cable length calibration
The 1503 was Tek's long-line (10km) TDR analyzer. IIRC, it put haversine pulses of about 5v onto the line under test (~10v open circuit). The 1502 (~600m line length) put pulses of about 200mV onto the line under test (~400mV open circuit). Best regards, Charles Scott wrote: This is highly dependent on the TDR especially ones designed for long twisted pair runs where a high voltage pulse is used to overcome resistive losses David had written: The Tektronix 1502 uses a tunnel diode pulser to produce a 50 picosecond output step of about 200 millivolts. There is a misprint in the theory section of the service manual which says "400 V" instead of "400mV". Scott had written: Time Domain Reflectrometry is the usual technique for finding cable length but even there the cables NVP is an essential parameter if you want to compute length but not essential in time nuts application because we are interested in delay which a TDR reads directly When using a TDR its best if cable is unterminated as the discontinuity at the end is helpful as a marker. Also most TDRs like the Tek 1502 can put 100v or more on the cable which will blow most GPS antennas ___ 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.
