Re: [time-nuts] WWV/CHU
On 30 March 2018 at 06:49, Tom Van Baak wrote: > > FYI: for the original spam-free version, please use: > > https://tf.nist.gov/general/pdf/469.pdf > > In general, if the author or paper is related to NIST, the original > copyright-free PDF will be available in the NIST Time and Frequency > Publication Database. That easily searchable database, and the thousands of > papers it contains, is probably the greatest asset we time nuts have. For > those of you that don't know it yet, check it out: > > https://tf.nist.gov/general/publications.htm That's useful to know. I have been in contact with someone at NPL, who provided papers by either 1) Attaching a copy. 2) Mentioning it was on Research Gate - a site I personally find annoying. 3) A link to IEEE (or similar), which will has a paywall. This suggests to me NPL don't have all their papers available online, although at least some can be found at http://www.npl.co.uk/publications/ For anyone interested in metrology, and I assume that includes everyone on this list, this NPL publication, "A beginner's guide to uncertainty of measurement." by Stephanie Bell http://www.npl.co.uk/publications/a-beginners-guide-to-uncertainty-in-measurement is well worth a read. This is far more readable than "Guide to the expression of uncertainty in measurement (GUM)", which is heavy going. > > As a non-academic working from home one of the greatest frustrations is > getting copies of old and new scientific articles. > You obviously share the same frustrations as Alexandra Elbakyan https://en.wikipedia.org/wiki/Alexandra_Elbakyan Because of her inability to get some papers, she set up sci-hub. https://en.wikipedia.org/wiki/Sci-Hub Alexandra Elbakyan makes the very valid point that authors do not get paid for submitting papers, reviewers do not get paid for reviewing them, yet the publishers charge significant amounts of money for distribution of electronic copies of papers. This is VERY different to books or music, where authors get royalties from copies sold. You can debate the ethics of sci-hub, with many scientists having strong and opposing views on sci-hub. The site does allow one to get virtually any academic paper for free. There are no ads, but donations are accepted by bitcoin - which reminds me, I must set up a bitcoin wallet so I can donate to sci-hub. 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] WWV/CHU
Hi > On Mar 30, 2018, at 12:42 AM, Hal Murray wrote: > > > jim...@earthlink.net said: >> Hal, you should know better than to have a question like "get time" on this >> list without specify the precision and accuracy . > > I was thinking of measuring the results, and maybe comparing various > receivers if I get that far. > > "Good enough" for me would be to see the change in prop delay from night to > day. > > >> I was in a meeting yesterday with a lot of technical people, discussing >> testing an HF receiver, and I mentioned WWV as a source, and there were a >> combination of blank looks and amused/amazed looks (at the blank looks) - >> OK, so now we know who in the room are the computer only people (WWV? is >> that some sort of NTP protocol?) and who are the radio people > > I listened to WWV as a kid. I think my father told me about it. (We had a > good collection of old tube radios.) > > Roughly 40 years ago, a friend showed me a NBS booklet describing a scheme > for distributing time via TV. I forget the details. It was a cooperative > project with one of the major networks. Back in the era when the network stations all “went direct” to the mothership for their signal, all the sync pulses ultimately could be traced back to network HQ. That changed when local frame buffers (and other forms of translation) became the “way to do it”. The TV based sync timing survived in the Washington DC area longer than the rest of the country. It may even still be active ….. Bob > NBS published the propagation delays > which changed occasionally as the phone companies providing the underlying > links rerouted things. > > This is an IEEE article from 1972 that looks like a good fit: > Nationwide Precise Time and Frequency > Distribution Utilizing an Active Code Within > Network Television Broadcasts >DAVID A. HOWE > https://www.researchgate.net/publication/3092613 > > > > -- > 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] WWV/CHU
t...@leapsecond.com said: > In general, if the author or paper is related to NIST, the original > copyright-free PDF will be available in the NIST Time and Frequency > Publication Database. That easily searchable database, and the thousands of > papers it contains, is probably the greatest asset we time nuts have. For > those of you that don't know it yet, check it out: > https://tf.nist.gov/general/publications.htm Thanks. Another other great resource (non time-nut) is NIH Pubmed. I think the deal is that they get to distribute a copy of any paper from research that they finance. I think the publisher gets 6 months or a year before the NIH free version goes online. I assume the publishers freaked out when the idea was first announced. Anybody know of a paper discussing that issue? -- 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.
Re: [time-nuts] WWV/CHU
> This is an IEEE article from 1972 that looks like a good fit: > Nationwide Precise Time and Frequency > Distribution Utilizing an Active Code Within > Network Television Broadcasts >DAVID A. HOWE > https://www.researchgate.net/publication/3092613 FYI: for the original spam-free version, please use: https://tf.nist.gov/general/pdf/469.pdf In general, if the author or paper is related to NIST, the original copyright-free PDF will be available in the NIST Time and Frequency Publication Database. That easily searchable database, and the thousands of papers it contains, is probably the greatest asset we time nuts have. For those of you that don't know it yet, check it out: https://tf.nist.gov/general/publications.htm As a non-academic working from home one of the greatest frustrations is getting copies of old and new scientific articles. NIST seems to be the rare exception. Decade after decade, administration after administration, that database keeps working. > These are my opinions. I hate spam. Me too, which is why it's so frustrating to deal with web sites that scrap free PDF's and then serve them to you for a price or with a side of spam. There are even web sites that serve all our time-nuts postings along with injected targeted ads. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWV/CHU
jim...@earthlink.net said: > Hal, you should know better than to have a question like "get time" on this > list without specify the precision and accuracy . I was thinking of measuring the results, and maybe comparing various receivers if I get that far. "Good enough" for me would be to see the change in prop delay from night to day. > I was in a meeting yesterday with a lot of technical people, discussing > testing an HF receiver, and I mentioned WWV as a source, and there were a > combination of blank looks and amused/amazed looks (at the blank looks) - > OK, so now we know who in the room are the computer only people (WWV? is > that some sort of NTP protocol?) and who are the radio people I listened to WWV as a kid. I think my father told me about it. (We had a good collection of old tube radios.) Roughly 40 years ago, a friend showed me a NBS booklet describing a scheme for distributing time via TV. I forget the details. It was a cooperative project with one of the major networks. NBS published the propagation delays which changed occasionally as the phone companies providing the underlying links rerouted things. This is an IEEE article from 1972 that looks like a good fit: Nationwide Precise Time and Frequency Distribution Utilizing an Active Code Within Network Television Broadcasts DAVID A. HOWE https://www.researchgate.net/publication/3092613 -- 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.
Re: [time-nuts] WWV/CHU
I'll add to the conversation. CHU is easier to deal with because its not a subcarrier as the 100 Hz WWV signal is. Its FSK and bell 103 modem style. Regards Paul WB8TSL On Thu, Mar 29, 2018 at 10:08 AM, jimlux wrote: > On 3/29/18 3:49 AM, Attila Kinali wrote: > >> On Thu, 29 Mar 2018 03:12:24 -0700 >> Hal Murray wrote: >> >> What do I need in in order to get time from WWV or CHU? >>> >>> Do I need a fancy receiver as a front end? Do I have a chance with one >>> of >>> the low cost USB thumb drive size receivers? >>> >>> Is there an obvious software package to start with? (Linux) >>> >> >> I think the easiest is GnuRadio... A quick googling lead >> to https://github.com/jasonabele/gr-wwvb >> I don't know anything about it so use at own risk :) >> But at least it seems like something that can be done easily >> on a rainy evening. >> >> Normal RTL-SDR's do not work for WWVB as they have a lower cut of >> frequency in the range of 20-50MHz...unless you bypass the tuner >> chip and feed the signal directly to the ADC. As IIRC all RTL-SDR >> give you something like 2Msps, that should be more than plenty to >> decode WWVB and related signals. If you feed the RTL-SDR from an >> external frequency source, you should be able to related that >> frequency source to WWV. >> > > The RTL-SDR is an interesting device - I'm putting together a hobby HF > interferometer with GPS to provide time tags. > > Yes, most of the newer parts (RTL-SDR v3, for instance) provide a > programmable bypass of the front end downconverter (the part is actually > designed to tune TV signals and the L-band output of a consumer dish LNB) > The backend chip (RTL2832U) is a digital downconverter which mixes and > filters the nominal 3.5 MHz IF which is sampled at 28.8 MHz > > You can actually adjust the output sample rate - something around 2 > Msample/second is the default, but there's lots of other rates available. > For WWV you could crank it down, but.. > The ADC is 8 bits (7 ENOB) and the output is 8 bit I/8 bit Q. > > Folks have modified the RTL-SDR to accept an external frequency reference, > so you could take the output from your ensemble of Cesium references to > discipline a hydrogen maser (so your close in phase noise is better),then > use that to drive a 28.8 MHz discrete divide/multiply chain, and run that > into your $30 receiver to improve the frequency accuracy. (not for nothing > are we called time-nuts) > > > > > >> Attila Kinali >> >> > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/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] WWV/CHU
Hi There are a *lot* of HF receiver gizmos out there these days. Is $5 to much to spend? Does the budget make it up to $300? Do you want to pick up *every* time transmission at once? (as constrained by propagation). For something like 5 MHz / 10 MHz WWVB plus CHU, there are $20 demo boards that look like they would do the trick as.a direct sampling device. I haven’t tried one yet. I have no idea how well they actually do. My guess is that at HF, propagation will limit the usefulness of the carrier as a stable signal. Anything that will drift less than a few 10’s of Hz is going to do fine to pick up the audio. That’s not all that crazy hard at 10 MHz. Once you do get the time ticks off of the audio, you still have a “millisecond” level accuracy signal due to propagation. You also have a signal that will drop out from time to time ( unless you live in Colorado). Bob > On Mar 29, 2018, at 10:08 AM, jimlux wrote: > > On 3/29/18 3:49 AM, Attila Kinali wrote: >> On Thu, 29 Mar 2018 03:12:24 -0700 >> Hal Murray wrote: >>> What do I need in in order to get time from WWV or CHU? >>> >>> Do I need a fancy receiver as a front end? Do I have a chance with one of >>> the low cost USB thumb drive size receivers? >>> >>> Is there an obvious software package to start with? (Linux) >> I think the easiest is GnuRadio... A quick googling lead >> to https://github.com/jasonabele/gr-wwvb >> I don't know anything about it so use at own risk :) >> But at least it seems like something that can be done easily >> on a rainy evening. >> Normal RTL-SDR's do not work for WWVB as they have a lower cut of >> frequency in the range of 20-50MHz...unless you bypass the tuner >> chip and feed the signal directly to the ADC. As IIRC all RTL-SDR >> give you something like 2Msps, that should be more than plenty to >> decode WWVB and related signals. If you feed the RTL-SDR from an >> external frequency source, you should be able to related that >> frequency source to WWV. > > The RTL-SDR is an interesting device - I'm putting together a hobby HF > interferometer with GPS to provide time tags. > > Yes, most of the newer parts (RTL-SDR v3, for instance) provide a > programmable bypass of the front end downconverter (the part is actually > designed to tune TV signals and the L-band output of a consumer dish LNB) > The backend chip (RTL2832U) is a digital downconverter which mixes and > filters the nominal 3.5 MHz IF which is sampled at 28.8 MHz > > You can actually adjust the output sample rate - something around 2 > Msample/second is the default, but there's lots of other rates available. > For WWV you could crank it down, but.. > The ADC is 8 bits (7 ENOB) and the output is 8 bit I/8 bit Q. > > Folks have modified the RTL-SDR to accept an external frequency reference, so > you could take the output from your ensemble of Cesium references to > discipline a hydrogen maser (so your close in phase noise is better),then use > that to drive a 28.8 MHz discrete divide/multiply chain, and run that into > your $30 receiver to improve the frequency accuracy. (not for nothing are we > called time-nuts) > > > > >> Attila Kinali > > ___ > 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] WWV/CHU
On 3/29/18 3:49 AM, Attila Kinali wrote: On Thu, 29 Mar 2018 03:12:24 -0700 Hal Murray wrote: What do I need in in order to get time from WWV or CHU? Do I need a fancy receiver as a front end? Do I have a chance with one of the low cost USB thumb drive size receivers? Is there an obvious software package to start with? (Linux) I think the easiest is GnuRadio... A quick googling lead to https://github.com/jasonabele/gr-wwvb I don't know anything about it so use at own risk :) But at least it seems like something that can be done easily on a rainy evening. Normal RTL-SDR's do not work for WWVB as they have a lower cut of frequency in the range of 20-50MHz...unless you bypass the tuner chip and feed the signal directly to the ADC. As IIRC all RTL-SDR give you something like 2Msps, that should be more than plenty to decode WWVB and related signals. If you feed the RTL-SDR from an external frequency source, you should be able to related that frequency source to WWV. The RTL-SDR is an interesting device - I'm putting together a hobby HF interferometer with GPS to provide time tags. Yes, most of the newer parts (RTL-SDR v3, for instance) provide a programmable bypass of the front end downconverter (the part is actually designed to tune TV signals and the L-band output of a consumer dish LNB) The backend chip (RTL2832U) is a digital downconverter which mixes and filters the nominal 3.5 MHz IF which is sampled at 28.8 MHz You can actually adjust the output sample rate - something around 2 Msample/second is the default, but there's lots of other rates available. For WWV you could crank it down, but.. The ADC is 8 bits (7 ENOB) and the output is 8 bit I/8 bit Q. Folks have modified the RTL-SDR to accept an external frequency reference, so you could take the output from your ensemble of Cesium references to discipline a hydrogen maser (so your close in phase noise is better),then use that to drive a 28.8 MHz discrete divide/multiply chain, and run that into your $30 receiver to improve the frequency accuracy. (not for nothing are we called time-nuts) Attila Kinali ___ 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] WWV/CHU
On 3/29/18 3:12 AM, Hal Murray wrote:
What do I need in in order to get time from WWV or CHU?
Do I need a fancy receiver as a front end? Do I have a chance with one of
the low cost USB thumb drive size receivers?
Is there an obvious software package to start with? (Linux)
Hal,
you should know better than to have a question like "get time" on this
list without specify the precision and accuracy .
I was in a meeting yesterday with a lot of technical people, discussing
testing an HF receiver, and I mentioned WWV as a source, and there were
a combination of blank looks and amused/amazed looks (at the blank
looks) - OK, so now we know who in the room are the computer only people
(WWV? is that some sort of NTP protocol?) and who are the radio people
The little HF dongle receivers will certainly receive HF WWV or WWVH, if
propagation supports it, and you can listen to the dulcet tones of the
appropriately gendered announcer ("at the tone, the time will be twelve
hours thirty four minutes coordinated universal time") - you could
probably track and decode the tone/ticks. I would think that if you can
hear the voice, you can decode the 100 Hz subcarrier, but I've not tried
it. You can see the 100 Hz on a spectrum analysis display.
I would think that you can get propagation limited accuracy with the
RTL-SDR type receiver.
Antenna is going to be the big challenge - the little whip antenna for
the dongle won't usually cut it.
___
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] WWV/CHU
Hi If you are running 10 MHz as your lab standard, you *will* have 10 MHz floating around. Add to that various 10 MHz OCXO’s here or there on the bench and you have even more odd stuff right at 10 MHz. Yes, if you run triple shield coax for your standard lines and your antenna is 1000’ from your lab, this may not be that big an issue. If you setup is a bit more modest, as WWV fades, the local stuff will be apparent. Bottom line - consider 5 MHz ( unless you are set up with that as your standard ….). Bob > On Mar 29, 2018, at 6:58 AM, Tim Shoppa wrote: > > It does not take a fancy receiver to hear WWV or CHU. Any super low end > shortwave portable (less than $100) will do fine. > > You then feed the audio into a PC with naps configured for NTP audio refclock. > > The wideband USB connected DSP receivers are neat and I am using one for > various purposes in the shack but not yet WWV. You would have to characterize > one and it’s computer based DSP processing for latency. > > Any such setup has to be characterized for latency (propagation + receiver+ > soundcard) anyway. Sub-millisecond accuracy is a reasonable goal. > > In continental US, one or more of the three 5/10/15 MHz WWV signals is > receivable most any time of day. NTP WWV software knows how to cycle one > particular model of receiver through the frequencies and can easily be > modified to work with other computer-controllable receivers. > > WWVH can be reliably heard for some of each day as well. > > A recent QST or QEX had a nice simple 10MHz WWV receiver in it. I think it > was oriented towards extracting 10MHz carrier and not for demodulating the > time code, however. > > Tim N3QE > >> On Mar 29, 2018, at 6:12 AM, Hal Murray wrote: >> >> >> What do I need in in order to get time from WWV or CHU? >> >> Do I need a fancy receiver as a front end? Do I have a chance with one of >> the low cost USB thumb drive size receivers? >> >> Is there an obvious software package to start with? (Linux) >> >> >> -- >> 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. ___ 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] WWV/CHU
It does not take a fancy receiver to hear WWV or CHU. Any super low end shortwave portable (less than $100) will do fine. You then feed the audio into a PC with naps configured for NTP audio refclock. The wideband USB connected DSP receivers are neat and I am using one for various purposes in the shack but not yet WWV. You would have to characterize one and it’s computer based DSP processing for latency. Any such setup has to be characterized for latency (propagation + receiver+ soundcard) anyway. Sub-millisecond accuracy is a reasonable goal. In continental US, one or more of the three 5/10/15 MHz WWV signals is receivable most any time of day. NTP WWV software knows how to cycle one particular model of receiver through the frequencies and can easily be modified to work with other computer-controllable receivers. WWVH can be reliably heard for some of each day as well. A recent QST or QEX had a nice simple 10MHz WWV receiver in it. I think it was oriented towards extracting 10MHz carrier and not for demodulating the time code, however. Tim N3QE > On Mar 29, 2018, at 6:12 AM, Hal Murray wrote: > > > What do I need in in order to get time from WWV or CHU? > > Do I need a fancy receiver as a front end? Do I have a chance with one of > the low cost USB thumb drive size receivers? > > Is there an obvious software package to start with? (Linux) > > > -- > 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] WWV/CHU
On Thu, 29 Mar 2018 03:12:24 -0700 Hal Murray wrote: > What do I need in in order to get time from WWV or CHU? > > Do I need a fancy receiver as a front end? Do I have a chance with one of > the low cost USB thumb drive size receivers? > > Is there an obvious software package to start with? (Linux) I think the easiest is GnuRadio... A quick googling lead to https://github.com/jasonabele/gr-wwvb I don't know anything about it so use at own risk :) But at least it seems like something that can be done easily on a rainy evening. Normal RTL-SDR's do not work for WWVB as they have a lower cut of frequency in the range of 20-50MHz...unless you bypass the tuner chip and feed the signal directly to the ADC. As IIRC all RTL-SDR give you something like 2Msps, that should be more than plenty to decode WWVB and related signals. If you feed the RTL-SDR from an external frequency source, you should be able to related that frequency source to WWV. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] WWV/CHU
What do I need in in order to get time from WWV or CHU? Do I need a fancy receiver as a front end? Do I have a chance with one of the low cost USB thumb drive size receivers? Is there an obvious software package to start with? (Linux) -- 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.
