Re: [time-nuts] WWVB BPSK Receiver Project?
In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I have considered FPGA, DSP would probably be more suitable, but if I can do it in an ARM with C/Assy code, I prefer that. I think Poul-Henning is refering to his AducLoran receiver, That's one of the few experiements I bothered to document, I've been doing similar stuff with DCF77 phase-code etc. As long as you're after time/freq, you can use very deep averaging which only takes a few instructions per sample, so for instance the 42MHz Aduc7026 chip copes nicely with a single Loran-C signal. I think I could squeeze a Loran-C navigation solution into it, if I wanted to and as long as we're not talking too high speeds (again allowing deep averaging) but I have not bothered. A modern PC has a lot of computing power for stuff like this, and is great for prototyping code, before dumping into a smaller chip. That's how I found out that the circular-buffer averaging comb-filter is a much better and stronger signal discriminator than almost anything else you can come up with, for frequency/phase reception. See for instance: http://phk.freebsd.dk/loran-c/CW/ -- 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] WWVB BPSK Receiver Project?
On Thu, Mar 15, 2012 at 2:51 PM, Attila Kinali att...@kinali.ch wrote: After the discussion here, i had a similar idea. I want to use the STM32F4xx for something bigger and bought two discovery boards to get used to them. But i didn't know what i want to do... it should be something usefull.. at least half way usefull. And the discussion here prodded me that i could do a SDR DCF77 with that. A 160MHz 32bit uC with hardware single precision floatingpoint is way more than fast enough to handle that :- You might want to choose a platform that can run either dttsp or Gnuradio/GRC or else you will be writing from scratch. You will spend weeks doing what could be done in hours. Look at these http://dttsp.sourceforge.net/ http://www.oz9aec.net/index.php/gnu-radio/grc-examples Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project? (fwd)
In message Pine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
--
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.
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Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
On Thu, 15 Mar 2012 22:27:53 +
Poul-Henning Kamp p...@phk.freebsd.dk wrote:
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
How good would that DAC need to be?
1-4MB RAM
over a 256kB RAM it's get pretty thin if you want to stay in the uC
busines. Unless you want to use an ARM9 or better with external SDRAM
and Flash. But those are mostly BGA (very few QFP chips out there) and
they are assumed to run Linux or Windows CE on them... Support for bare
metal stuff is pretty thin.
On the other hand, if you dont have to support an OS and work on the
bare metal, you can get away with very little RAM. 128k is a damn lot
if you have to fill it with usefull data structures ;-)
USB2 interface
Which would mean you need a pretty recent chip as HighSpeed USB has not
been introduced into the uC world for more than 2 years or so.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
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Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom.Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second.An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project?
PHK, I'm interested in your circular averaging buffer: suppose 1K long, the 1st sample goes into position 0, the 2nd into 1 ... the 1000th into 999 or, the 1st gets scaled and then summed with that already present in position 0 then the result back in position 0? And so on, of course, for position 1, 2 ... On Thu, Mar 15, 2012 at 11:48 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom.Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second.An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project?
That would be big expensive filter. All you really need is the average of the last N samples. But with WWVB the bits are amplitude modulated at one bit per second. so you want a big time constant on any AGC, maybe 100 seconds. If you are sampling at 192K that would use way to much memory if you stored each sample. Better to only keep running statistics.For AGC you don't need to process every sample, you can feed the AGC a subset of the sample stream. But with a 24b-t ADC you may not need AGC On Thu, Mar 15, 2012 at 4:01 PM, Azelio Boriani azelio.bori...@screen.it wrote: PHK, I'm interested in your circular averaging buffer: suppose 1K long, the 1st sample goes into position 0, the 2nd into 1 ... the 1000th into 999 or, the 1st gets scaled and then summed with that already present in position 0 then the result back in position 0? And so on, of course, for position 1, 2 ... On Thu, Mar 15, 2012 at 11:48 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom. Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second. An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ 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. -- Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project?
On 3/15/12 8:10 AM, J. Forster wrote: Why make it simple when complicated also works? -John Can't get your doctorate doing something someone else has already done...grin Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ 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] WWVB BPSK Receiver Project?
On 3/15/12 3:24 PM, Chris Albertson wrote: On Thu, Mar 15, 2012 at 2:51 PM, Attila Kinaliatt...@kinali.ch wrote: After the discussion here, i had a similar idea. I want to use the STM32F4xx for something bigger and bought two discovery boards to get used to them. But i didn't know what i want to do... it should be something usefull.. at least half way usefull. And the discussion here prodded me that i could do a SDR DCF77 with that. A 160MHz 32bit uC with hardware single precision floatingpoint is way more than fast enough to handle that :- You might want to choose a platform that can run either dttsp or Gnuradio/GRC or else you will be writing from scratch. You will spend weeks doing what could be done in hours. Look at these http://dttsp.sourceforge.net/ documentation for dttsp is less than wonderful http://www.oz9aec.net/index.php/gnu-radio/grc-examples seems to be a bit more diverse usage for gnuradio, so more examples and documentation Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project? (fwd)
On 3/15/12 3:27 PM, Poul-Henning Kamp wrote:
In messagePine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
and if you have any sort of processing behind the 1MSPS, you can do a
simple digital filter and decimate.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
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Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 9:41 PM, Chris Albertson wrote: On Thu, Mar 15, 2012 at 8:45 PM, Jim Luxjim...@earthlink.net wrote: http://dttsp.sourceforge.net/ documentation for dttsp is less than wonderful http://www.oz9aec.net/index.**php/gnu-radio/grc-exampleshttp://www.oz9aec.net/index.php/gnu-radio/grc-examples seems to be a bit more diverse usage for gnuradio, so more examples and documentation dttsp has by far the larger in-use user based because it is the engine used by PowerSDR by Flex Radio. It is also used by the HPSDR group. See these links http://www.flex-radio.com/ http://openhpsdr.org/ But you are right in that using dttsp is something that might take a long tome to learn. The above user group tends to have many appliance users and a few programers so learning is not so much of an issue If there are more than half a dozen people actually using dttsp, in the sense of modifying it, or doing something other than creating a UI for it, I'd be pretty surprised. It's pretty much a product of the two main authors. As you say, the learning curve is exceedingly steep, especially if you want to understand the architecture and internal structure. You could probably go in and do spot changes without breaking too much, but any sort of radical change (like adding a new demodulator) would be a pretty big challenge. The fact that it's the core of PowerSDR means that over the years, it's had a lot of customization for that particular application. Someone trying to decode PSK WWVB isn't going to be interested in the latency of the CW keyer or the performance of the automated notch filter. GNU Radio is popular in Universities where as soon as something works they toss it out. It's quite a bit easier to program or if you like there is GRC that allows visual programming.I think this is better because it allows a wider number of people to contribute. it's much more componentized and the source of the components is broader. Probably not as finished as something like PowerSDR, but much easier to bite off small chunks. For simple tasks, there are also tools like DL4YHF(?) spectrumlab. http://www.qsl.net/d/dl4yhf/spectra1.html it has: # Decoder for some time-code transmitters: MSF(60kHz), HBG(75kHz), DCF77 (77.5kHz) can now be used to set your PC clock to a high accuracy. All you need is your longwave receiver and the soundcard. # Modulator and decoder for some 'experimental' digital communication modes like PSK31, BPSK, QPSK, FSK, multi-tone HELL, MSK (minimum shift keying since 2004-12), transmission and reception of letters with a small 'terminal' window. I've used it a lot for a variety of tasks (a Doppler radar, for one thing) My suggestion to use a platform where these two libraries run was really to say that you should not write this on bare hardware. It's a good way to paint yourself into a corner and have to start over to add some new feature we can't think of today. Another idea, if you have access (e.g. student licenses or thru work) is Matlab/Simulink and real-time-workshop. All the building blocks are there, you just hook them up. Pretty pricey if you're not in the educational bucket, though. And Octave doesn't really have all the cool toolboxes that Matlab does. ___ 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] WWVB BPSK Receiver Project?
Frankly, my dear, I'd rather be a generalist. -John On 3/15/12 8:10 AM, J. Forster wrote: Why make it simple when complicated also works? -John Can't get your doctorate doing something someone else has already done...grin Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ 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] WWVB BPSK Receiver Project?
Hi: I sure would like a WWVB BPSK receiver for the new modulation. The processing gains described in the paper John Seamons linked describes processing gains that are tens of dB above what's possible with the old AM data format. John has also measures the experimental phase modulation testing, see: http://www.jks.com/wwvb/wwvb.html The WWB paper New Improved System for WWVB Broadcast given at the 43rd PTTI November 2011 is at: http://jks.com/wwvb.pdf Part of the processing gain comes directly from the BPSK modulation and that amounts to a little over 10 dB improvement, but there's a further 18 dB gain to be had by accumulating an hours worth of data and processing that. I'm sure in time there will be plenty of low cost ICs designed to receive the new signal, but my guess is that many Time Nuts would like to be in on the ground floor. Also NIST probably would like to get reports on the new signal when they do test transmissions. How to move forward? -- Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html ___ 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] WWVB BPSK Receiver Project?
In message 4f6116ce.7080...@pacific.net, Brooke Clarke writes: I sure would like a WWVB BPSK receiver for the new modulation. I've been playing with SDR and VLF signals for ages. What you want is an antenna, a 1MSPS ADC and a fast-ish CPU. One very interesting thing you can do with that, is to make a buffer 1000 samples long, and continously average the received signal into it, round-robin format. That amounts to a comb-filter for every n*1kHz signal, and a trivial sin/cos multiplicator will give you the phase and amplitude of every single radiotransmitter on n*1kHz up to your antialias filter at the same time. If you have CPU power, you can also receive Loran-C by making the buffer GRI*10 (or *20, if you want the code) samples long. I've long thought about building a board with one of the faster ARM CPUs and a 1MSPS 16bit ADC for this, but nobody else seemed interested, so I've just used my hacked up rig. -- 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] WWVB BPSK Receiver Project?
The first move will be to familiarize with this new modulation format. Of course I can't receive the WWVB but the DCF77 maybe a good test for me. On Wed, Mar 14, 2012 at 11:08 PM, Brooke Clarke bro...@pacific.net wrote: Hi: I sure would like a WWVB BPSK receiver for the new modulation. The processing gains described in the paper John Seamons linked describes processing gains that are tens of dB above what's possible with the old AM data format. John has also measures the experimental phase modulation testing, see: http://www.jks.com/wwvb/wwvb.html The WWB paper New Improved System for WWVB Broadcast given at the 43rd PTTI November 2011 is at: http://jks.com/wwvb.pdf Part of the processing gain comes directly from the BPSK modulation and that amounts to a little over 10 dB improvement, but there's a further 18 dB gain to be had by accumulating an hours worth of data and processing that. I'm sure in time there will be plenty of low cost ICs designed to receive the new signal, but my guess is that many Time Nuts would like to be in on the ground floor. Also NIST probably would like to get reports on the new signal when they do test transmissions. How to move forward? -- Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html ___ 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] WWVB BPSK Receiver Project?
Dear Time-Nuts, (new at this list, but reading for long time excellent timekeeping oscillator articles) I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the new signal, but my guess is that many Time Nuts would like to be in on the ground floor. Also NIST probably would like to get reports on the new signal when they do test transmissions. How to move forward? I have no experience with WWVB, since I live in central Europe, but some time ago I received quite well German DCF77 (77.5kHz) using absolutely simplistic circuit with no tuned parts except very tolerant ferrite rod antenna. The point was direct sampling into an ADC and doing all the business in a SDR fashion. I wanted to do PRBS PSK tracking and also PLL-less clock disciplining this way, but there were another priorities, though. However, if anybody would be interested in, I would be happy to return to these nice LF circuits. Greetings from Marek P.s A very little bit from DCF77, but only the pre-SDR stage: http://www.youtube.com/watch?v=Fx9bas49Uow ___ 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] WWVB BPSK Receiver Project?
All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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] WWVB BPSK Receiver Project?
On Wed, Mar 14, 2012 at 3:08 PM, Brooke Clarke bro...@pacific.net wrote: Hi: I sure would like a WWVB BPSK receiver for the new modulation. The processing gains described in the paper John Seamons linked describes processing gains that are tens of dB above what's possible with the old AM data format. John has also measures the experimental phase modulation testing, see: http://www.jks.com/wwvb/wwvb.html The WWB paper New Improved System for WWVB Broadcast given at the 43rd PTTI November 2011 is at: http://jks.com/wwvb.pdf Part of the processing gain comes directly from the BPSK modulation and that amounts to a little over 10 dB improvement, but there's a further 18 dB gain to be had by accumulating an hours worth of data and processing that. I'm sure in time there will be plenty of low cost ICs designed to receive the new signal, but my guess is that many Time Nuts would like to be in on the ground floor. Also NIST probably would like to get reports on the new signal when they do test transmissions. How to move forward? I'd say to go 100% SDR. In other words a simple front and that pushes as much of the functionality into software as possible. The carrier is only 60K. That is low enough that one can directly digitize the RF using an ADC that samples at only 192K/sec. 192K/Sec is a common sample rte for high-end audio and you can buy a 24-bit dual channel interface for under $200. So I'd use an antenna (the best would be a shielded loop with many turns of wire but ferrite loop stick could work) Follow that be an RF amp and very narrow filter and then the above 24-bit 192K ADC. With a 24-bit ADC you may not need any automatic gain control. So yo are almost sampling the voltage off the antenna, so that's why I called it 100% SDR Once the data are inside the computer the very next step might be an FFT. Some good easy to use software is this: http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion Using this you simply drop function blocks on a screen and connect then with lines. It's a visual drag and drop way to build a signal processor As an example to build a spectrum analyzer you drop a block the represents your audio interface, another for the FFT operator and a third for a graph. Connect them together.Then plug in a microphone and point it as something you want to plot. If you do use the simplest possible RF front and that can still work, followed by a common off the shelf audio interface and then a simple graphical programming environment you then will have a wider community of people working on this.You could use more complex technology like an FPGA or a DSP chip but then the number of people who would know how to help will be a number close to zero. The RF front end does not need to be sophisticated because much of the selectivity and gain control is done in software. You just need a hard low pass filter to remove everything above 60KHz -- Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html ___ 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. -- Chris Albertson Redondo Beach, California ___ 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] WWVB BPSK Receiver Project?
Asus has a $30 Xonar PCI soundcard that should do the job. I have two of the the more expensive pci-e versions. Some motherboards can do a/d at 192 but not as well as the Xonar. I made a 60 KHz antenna by winding a zillion turns on a ferrite rod and a padder going into the gate of a FET. This was in the 1970s. On 03/14/2012 03:35 PM, Chris Albertson wrote: On Wed, Mar 14, 2012 at 3:08 PM, Brooke Clarkebro...@pacific.net wrote: Hi: I sure would like a WWVB BPSK receiver for the new modulation. The processing gains described in the paper John Seamons linked describes processing gains that are tens of dB above what's possible with the old AM data format. John has also measures the experimental phase modulation testing, see: http://www.jks.com/wwvb/wwvb.html The WWB paper New Improved System for WWVB Broadcast given at the 43rd PTTI November 2011 is at: http://jks.com/wwvb.pdf Part of the processing gain comes directly from the BPSK modulation and that amounts to a little over 10 dB improvement, but there's a further 18 dB gain to be had by accumulating an hours worth of data and processing that. I'm sure in time there will be plenty of low cost ICs designed to receive the new signal, but my guess is that many Time Nuts would like to be in on the ground floor. Also NIST probably would like to get reports on the new signal when they do test transmissions. How to move forward? I'd say to go 100% SDR. In other words a simple front and that pushes as much of the functionality into software as possible. The carrier is only 60K. That is low enough that one can directly digitize the RF using an ADC that samples at only 192K/sec. 192K/Sec is a common sample rte for high-end audio and you can buy a 24-bit dual channel interface for under $200. So I'd use an antenna (the best would be a shielded loop with many turns of wire but ferrite loop stick could work) Follow that be an RF amp and very narrow filter and then the above 24-bit 192K ADC. With a 24-bit ADC you may not need any automatic gain control. So yo are almost sampling the voltage off the antenna, so that's why I called it 100% SDR Once the data are inside the computer the very next step might be an FFT. Some good easy to use software is this: http://gnuradio.org/redmine/projects/gnuradio/wiki/GNURadioCompanion Using this you simply drop function blocks on a screen and connect then with lines. It's a visual drag and drop way to build a signal processor As an example to build a spectrum analyzer you drop a block the represents your audio interface, another for the FFT operator and a third for a graph. Connect them together.Then plug in a microphone and point it as something you want to plot. If you do use the simplest possible RF front and that can still work, followed by a common off the shelf audio interface and then a simple graphical programming environment you then will have a wider community of people working on this.You could use more complex technology like an FPGA or a DSP chip but then the number of people who would know how to help will be a number close to zero. The RF front end does not need to be sophisticated because much of the selectivity and gain control is done in software. You just need a hard low pass filter to remove everything above 60KHz -- Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html ___ 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. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] WWVB BPSK Receiver Project?
I will share my few bits of worked experience. But it may seem obvious. I'd say to go 100% SDR. In other words a simple front and that pushes as much of the functionality into software as possible. The carrier is only 60K. That is low enough that one can directly digitize the RF using an ADC that samples at only 192K/sec. Not necesarilly. I received 77.5kHz very well in first sampling mirror, sampling using ADS7813 16bit ADC @44ksps, yielding carrier at 10.5kHz in discrete-time domain. 192K/Sec is a common sample rte for high-end audio and you can buy a 24-bit dual channel interface for under $200. Beware, there are lots of sigma-delta ADCs for this purpose and I am in doubt whether they could perform better than less-bits SAR ADC. So I'd use an antenna (the best would be a shielded loop with many turns of wire but ferrite loop stick could work) Follow that be an RF amp and very narrow filter and then the above 24-bit 192K ADC. I must object a little bit against RF and very narrow -- I have used very slw amplifiers (they were in a shack, original purpose DC measurement up to some 100s of kHz) and nothing narrow (or even tuned) -- except the ferrite rod itself. The rest were 2 ICs (amp ADC) and simple RC network. Worked very well, including few centimeters from laptop's CCFL inverter. Best regards, Marek ___ 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] WWVB BPSK Receiver Project?
In message Pine.LNX.4.64.1203142345310.2459@tesla, Marek Peca writes: I will share my few bits of worked experience. But it may seem obvious. I'd say to go 100% SDR. In other words a simple front and that pushes as much of the functionality into software as possible. The carrier is only 60K. That is low enough that one can directly digitize the RF using an ADC that samples at only 192K/sec. Not necesarilly. I received 77.5kHz very well in first sampling mirror, sampling using ADS7813 16bit ADC @44ksps, yielding carrier at 10.5kHz in discrete-time domain. Here's a really interesting platform for VLF SDR work: http://www.seeedstudio.com/depot/dso-nano-v2-p-681.html?cPath=174 1MSPS 12 bit ADC, input amplifier/attenuator, display, USB interface, and rechargeable lithium battery. For $89... Too bad it doesn't have a 10MHz reference clock input for time-nuttery. -- 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] WWVB BPSK Receiver Project?
Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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] WWVB BPSK Receiver Project?
Brooke, As I've said, I don't care about the Time. The time determined by the start of TV or radio programs is plenty good enough to keep any appointments. My only interest is as a standard of Time Interval as a reference for synthesizers, counters, etc. If you think about it, unless you are doing something like occultation or eclipse timing or eBay, the ToD rarely matters. They killed LORAN, which worked beautifully. Now it looks like they are going to kill WWVB, which is a bit more involved, but works. GPS is not an option without a tall tower. This is NOT progress, IMO. -John == Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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] WWVB BPSK Receiver Project?
I am afraid that like John my concern is the frequency reference. Time? Heck it comes by the internet, WWV or GPS and lastly good old watches that do pretty well these days. No comments on celphones. So the term is screwed. All of the sampling and computer processing may indeed loose the primary reference quality for frequency measurement. So is all lost? Well maybe not completely. Those old receivers are actually pretty nice for filtering the incoming signal and such. A Singer I have has a good collins 60 Kc filter. So perhaps as a gain stage they still have value. It gets interesting at the next step and thats what to do about the reversals of the carrier. A question I have is this. Since the samples are actually slow on the comparison. Would a 117 even see it. Is it perhaps just adding additional filtering. All speculation on my part. I need to read the dock we have just received more carefully to get a better understanding. Happy to run up the fluke 207 and a 117 perhaps on the next set of tests and see what happens. (207 is actually Johns old unit) Also have a spectracom 8170. But thats really a clock and as stated should work fine. Regards Paul. WB8TSL On Wed, Mar 14, 2012 at 8:13 PM, J. Forster j...@quikus.com wrote: Brooke, As I've said, I don't care about the Time. The time determined by the start of TV or radio programs is plenty good enough to keep any appointments. My only interest is as a standard of Time Interval as a reference for synthesizers, counters, etc. If you think about it, unless you are doing something like occultation or eclipse timing or eBay, the ToD rarely matters. They killed LORAN, which worked beautifully. Now it looks like they are going to kill WWVB, which is a bit more involved, but works. GPS is not an option without a tall tower. This is NOT progress, IMO. -John == Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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] WWVB BPSK Receiver Project?
Brooke, In speaking with John Lowe of NIST (Group Leader for Time Frequency service), he stated that the absolute time recovery of their intended new modulation scheme is 10 milliseconds. Nothing stellar there ! BUT you are right, all of us that have hp-117 type receivers are just out of luck. John Lowe did say they are going to produce a PIC (Microchip) project that will grab the data stream and reconstruct the carrier signal so that can then be fed back into a hp-117 type receiver so it can still be used. However, he did say that is a dream at the moment as they have not really started to work on it. He then said I could do it and they would consider my efforts. While I had a number of thoughts running though mind when he said that; I did hold my comments back. I have to tell you, John Lowe sounded like he was drinking the Kool-Aid because I told him I was quite negative to the whole idea and he went into a nonstop mode of telling me all the good things that were going to come about with this modulation scheme. The same kind of hype that occurred with the HDTV. By the way, all those good things have nothing to do with anything Time-nutty except for pissing us off, as it were. His enthusiasm was aimed totally at new products. Although he admitted it leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold, he really did not seem to care. Pointing out that a failure with the GPS system left WWVB as the only alternate did not seem to matter either. OH Well, BillWB6BNQ Brooke Clarke wrote: Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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] WWVB BPSK Receiver Project?
OK thats great a maybe pic chip answer. They do cure all ill's after all. Really scratching my head here. But I do think there is an answer as long as the phase reversal is accurately controlled and still referenced to the reference standard. A I say I need to read. Regards Paul On Wed, Mar 14, 2012 at 9:14 PM, WB6BNQ wb6...@cox.net wrote: Brooke, In speaking with John Lowe of NIST (Group Leader for Time Frequency service), he stated that the absolute time recovery of their intended new modulation scheme is 10 milliseconds. Nothing stellar there ! BUT you are right, all of us that have hp-117 type receivers are just out of luck. John Lowe did say they are going to produce a PIC (Microchip) project that will grab the data stream and reconstruct the carrier signal so that can then be fed back into a hp-117 type receiver so it can still be used. However, he did say that is a dream at the moment as they have not really started to work on it. He then said I could do it and they would consider my efforts. While I had a number of thoughts running though mind when he said that; I did hold my comments back. I have to tell you, John Lowe sounded like he was drinking the Kool-Aid because I told him I was quite negative to the whole idea and he went into a nonstop mode of telling me all the good things that were going to come about with this modulation scheme. The same kind of hype that occurred with the HDTV. By the way, all those good things have nothing to do with anything Time-nutty except for pissing us off, as it were. His enthusiasm was aimed totally at new products. Although he admitted it leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold, he really did not seem to care. Pointing out that a failure with the GPS system left WWVB as the only alternate did not seem to matter either. OH Well, BillWB6BNQ Brooke Clarke wrote: Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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 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] WWVB BPSK Receiver Project?
In thinking about it a bit further, one might be able to take the 60 kHz received sine at some point in the receiver, full wave rectify and HP filter it (which doubles the frequency) then divide by two in a Flip-Flop and heavily filter the resultant. This is a hybrid solution... analog and digital... with not a uP in sight!! That would preserve the frequency, but ditch the phase reversals of the BPSK. Depending on the guts of the particular receiver, it might be possible to simply retrofit a PCB. The 180 degree phase reversal of the BPSK is just about the worst possible thing for a PLL of typical receicers. If the ratio of 1s to 0s is 50% the loop just thrashes. -John OK thats great a maybe pic chip answer. They do cure all ill's after all. Really scratching my head here. But I do think there is an answer as long as the phase reversal is accurately controlled and still referenced to the reference standard. A I say I need to read. Regards Paul On Wed, Mar 14, 2012 at 9:14 PM, WB6BNQ wb6...@cox.net wrote: Brooke, In speaking with John Lowe of NIST (Group Leader for Time Frequency service), he stated that the absolute time recovery of their intended new modulation scheme is 10 milliseconds. Nothing stellar there ! BUT you are right, all of us that have hp-117 type receivers are just out of luck. John Lowe did say they are going to produce a PIC (Microchip) project that will grab the data stream and reconstruct the carrier signal so that can then be fed back into a hp-117 type receiver so it can still be used. However, he did say that is a dream at the moment as they have not really started to work on it. He then said I could do it and they would consider my efforts. While I had a number of thoughts running though mind when he said that; I did hold my comments back. I have to tell you, John Lowe sounded like he was drinking the Kool-Aid because I told him I was quite negative to the whole idea and he went into a nonstop mode of telling me all the good things that were going to come about with this modulation scheme. The same kind of hype that occurred with the HDTV. By the way, all those good things have nothing to do with anything Time-nutty except for pissing us off, as it were. His enthusiasm was aimed totally at new products. Although he admitted it leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold, he really did not seem to care. Pointing out that a failure with the GPS system left WWVB as the only alternate did not seem to matter either. OH Well, BillWB6BNQ Brooke Clarke wrote: Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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 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] WWVB BPSK Receiver Project?
John Like your thought. I seem to remember costas loops work like that to recover the carrier. Paul, It recovers a bipolar signal to steer the local VCO as well as the data.. It also needs a quadratue hybrid at the VCO frequency (although it might be fairly easy to make a quadrature oscillator vat 60 kHz.) Had seen it in amsat many years ago. So perhaps an approach is to limit if possible the incoming signal. I'm not sure if it works properly with clipped (digital) dignals, off hand. Though further simple dumb thought. A NE602 or SA602 or also teh 612 series. All the same mixer circuit (Or multiplier)will double the incoming frequency if you delay the incoming by 90 degrees I think. Sine and Cosine are orthogonal. You need to do (Sine)*(Sine) sin^2 (wt) = 1/2(1 - cos (2wt) Its a sensitive chip and has a 17 db conversion gain and is $2.40 at digikey. 8 pin dip. though what ever the delay at 60KC thats a long delay. ;-) The delay (phase shift) is not needed. Best, -John = Regards Paul On Wed, Mar 14, 2012 at 10:12 PM, David I. Emery d...@dieconsulting.comwrote: On Wed, Mar 14, 2012 at 05:13:47PM -0700, J. Forster wrote: Now it looks like they are going to kill WWVB, which is a bit more involved, but works. GPS is not an option without a tall tower. Everything you say up to this makes perfect sense, but what makes you think GPS timing fails to work with less than a tall tower ? I believe it is readily possible to get to the 10-30 ns of UTC/TAI TOD area with just reasonable sky view, not 100% as implied by a tower. And certainly 1E-11 or 1E-12 frequency accuracy is also readily available with less than perfect sky view depending on your taus... Perhaps ultimate performance requires really unobstructed sky view in order to absolutely minimize multipath but then you are probably talking 1E-13 or better... This is NOT progress, IMO. Virtually ANY GPS timing solution ought to easily get you inside of a couple of microseconds of UTC/TAI, I am pretty sure it is quite difficult to get within 10-100 us with the current AM modulation of WWVB, possibly even 1-10 ms is difficult. And anything close to this requires accurate knowledge of geographic position and 60 KHz propagation corrections. I'm not clear how accurately one can resolve the phase transition in the new scheme, but I suspect probably unambiguously to 1 cycle of the 60 KHz... and from there is merely a function of how accurately one can resolve the phase of the 60 KHz.This potentially can supply a much higher resolution time hack than the AM envelope. The real question being how important is preserving backward compatibility with antique equipment versus better performance... I agree that ALWAYS is a trade off... -John == Hi John: They are going to maintain the existing AM modulation format so all the WWVB Atomic Clocks will still work. The phase modulation is added on top of that. Yes, I expect my HP 117 may no longer work, but I'd much rather have the improved s/n and timing accuracy. Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html J. Forster wrote: All very nice, but if this change renders all existing receivers useless. How does that improve things? All it does is wipe out all the existing phase tracking infrastructure. The only benefit is to the government who can reuse the WWVB transmitter and frequency allocation. Everybody else will have to buy new stuff. Sounds a lot like HDTV fiasco. Making jobs (in China or Korea) by making scrap. YMMV, -John == Dear Time-Nuts, I sure would like a WWVB BPSK receiver for the new modulation. (..) I'm sure in time there will be plenty of low cost ICs designed to receive the [SNIP} ___ 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. -- Dave Emery N1PRE/AE, d...@dieconsulting.com DIE Consulting, Weston, Mass 02493 An empty zombie mind with a forlorn barely readable weatherbeaten 'For Rent' sign still vainly flapping outside on the weed encrusted pole - in celebration of what could have been, but wasn't and is not to be now either. ___ 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
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/14/12 8:07 PM, J. Forster wrote: John Like your thought. I seem to remember costas loops work like that to recover the carrier. Paul, It recovers a bipolar signal to steer the local VCO as well as the data.. It also needs a quadratue hybrid at the VCO frequency (although it might be fairly easy to make a quadrature oscillator vat 60 kHz.) One easy scheme is to make your VCO run at a multiple and divide down to generate the two quadrature square waves. Had seen it in amsat many years ago. So perhaps an approach is to limit if possible the incoming signal. I'm not sure if it works properly with clipped (digital) dignals, off hand. Yes it will. Though further simple dumb thought. A NE602 or SA602 or also teh 612 series. All the same mixer circuit (Or multiplier)will double the incoming frequency if you delay the incoming by 90 degrees I think. Sine and Cosine are orthogonal. You need to do (Sine)*(Sine) sin^2 (wt) = 1/2(1 - cos (2wt) This is like the classic squaring technique to receive PN coded signals without knowing the code. (it's used in some codeless GPS receivers.. you can retrieve frequency and phase) ___ 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] WWVB BPSK Receiver Project?
I know I am not one of the good-ole-boys here but I'd say go 100% SDR with your PC without an external A/D converter. Ok, how would you do this? You use under sampling. Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. By the way Ten Tec patented an under sampling scheme many years ago when they started into the SDR business. ___ 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] WWVB BPSK Receiver Project?
On 3/14/12 8:07 PM, J. Forster wrote: John Like your thought. I seem to remember costas loops work like that to recover the carrier. Paul, It recovers a bipolar signal to steer the local VCO as well as the data.. It also needs a quadratue hybrid at the VCO frequency (although it might be fairly easy to make a quadrature oscillator vat 60 kHz.) One easy scheme is to make your VCO run at a multiple and divide down to generate the two quadrature square waves. Doesn't look like that works with the HP 117A. I don't know about other receivers. Had seen it in amsat many years ago. So perhaps an approach is to limit if possible the incoming signal. I'm not sure if it works properly with clipped (digital) dignals, off hand. Yes it will. Not w/o a quadrature drive to the mixer/multiplier. A square wave, multiplied by itself, has the same output as input. Though further simple dumb thought. A NE602 or SA602 or also teh 612 series. All the same mixer circuit (Or multiplier)will double the incoming frequency if you delay the incoming by 90 degrees I think. Sine and Cosine are orthogonal. You need to do (Sine)*(Sine) sin^2 (wt) = 1/2(1 - cos (2wt) This is like the classic squaring technique to receive PN coded signals without knowing the code. (it's used in some codeless GPS receivers.. you can retrieve frequency and phase) A Costas Loop recovers the bit stream and the carrier frequency (from the local VCO) from a BPSK. It is self syncronizing. I'm beginning to think that, for the HP 117A at least, a fix could be built on a small daughter board. Also, I think that NIST should do the engineering and maybe run the boards too. -John === ___ 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] WWVB BPSK Receiver Project?
Bill wrote: [BPSK] leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold To be fair to NIST, there really aren't many people using WWVB as a source of laboratory-grade timing signals. As others have pointed out, it isn't accurate enough for true time nut performance, and to get all of what it *is* capable of requires heroic efforts. So in truth, the real market for WWVB is not time nuts -- it is people who want to know the time of day to within a second (the atomic clock crowd). And there are LOTS of them. So the change is likely to provide a modest upgrade path for the vast majority of actual users, at the expense of a few die-hards (hobbyists, mostly) who are trying to get more out of an LF timing source than it is really capable of delivering. From a public policy standpoint it seems to make good sense, however much it may offend time nuts' sensibilities. 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.
