Re: [time-nuts] WWVB BPSK Receiver Project?
OK, John Forster and I have been kicking around a few things off line, and he suggested I should bring part of it back on line. Maybe I have a few details wrong, or maybe I have them right and some folks are unaware of them. My concern about the BPSK, and breaking my Spectracom oscillator, is really centered on loosing my NIST traceable reference oscillator. I don't care one bit what time of day it is. I wrote: I did poke around a bit, and it appears that WWVB is still an approved frequency standard, so any oscillator which is phased locked to WWVB qualifies as an NIST traceable standard reference oscillator, which is my only concern. John wrote: Good news! Thanks. I wrote: A GPS disciplined oscillator, regardless of how stable/accurate it may be, is not an NIST traceable standard unless NIST decides to certify the Naval Observatory as a standard. Or I suppose NIST could take over the GPS correction uploads.but I don't see that happening any time soon. That's really outside their mission boundary. Maybe a few things have changed in the metrology world in past few years, but the GPS based oscillators are controlled by the Naval Observatory clocks, not the NIST clocks. So while an HP-117 or a Spectracon 8160 oscillator phase locked to WWVB is by definition an NIST traceable standard so long as it is in lock and you have a valid lock history, a GPS unit, even though it may be just as stable an oscillator, isn't an NIST traceable standard without a whole lot of equipment to validate that NIST and the GPS system are in sync. (There is/was actually a commercial solution to verify this, but it isn't/wasn't cheap.) For all you metrology guys out there, has any of this recently changed? So my interest in keep my Spectracom going isn't just to keep a stable 10 MHz oscillator in the lab. The GPS will give me a stable signal. My interest is in keeping a stable and traceable 10 MHz signal going. After all, all our old gray-hair tax dollars paid for this government service over the past 5 decades. Why should we get kicked off the bus now? It isn't like we want anything new. Just don't break what we've already paid for. Michael ___ 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?
Looks like this bounced as I sent from the wrong address. Better late than never. On Wed, 14 Mar 2012 15:46:48 -0700, Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: 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. Even better: a USB DVB card [1]. For $30 you have a few million 8-bit I/Q samples per second and an interface to Gnu Radio. The possibilities are nearly endless. Cheers, - Ben [1] http://sdr.osmocom.org/trac/wiki/rtl-sdr ___ 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 595370411-1332118092-cardhu_decombobulator_blackberry.rim.net-18097 4826-@b1.c24.bise6.blackberry, shali...@gmail.com writes: I was not concerned about processing power on a PC (or Mac for that matter) but for the uC that was used in PHK's project. That was sort of the entire point about the aducLoran: to show that for time-nuttery, you don't need much CPU. If you wanted to extract a real-time modulation of any kind, the situation is very different, but as long as you just want to extract a carrier phase/frequency, averaging is the way to go and that is cheap. -- 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? (fwd)
In message 4f669a4d.3010...@lazygranch.com, gary writes: DC in a transformer raises the low frequency corner a bit. Obviously not a problem in your case. I just double-checked, because that rang a bell. I did reinstate the capacitors as 2.2uF films in the final article for exactly that reason. As for gain, I have never missed any, I get a good healthy signal, even though I do live in the middle of a pop 30k city. I should point out that every active device Lankford puts in the signal chain [...] Why are you talking about Lankford at this point ? What I built was Fig 5 from this: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf I realize that Chris Trask started out from Lankfords design, but I don't think it is fair to attribute the Fig 5 schematic to Lankford any more. There's a picture of my implementation here: http://phk.freebsd.dk/misc/ChrisTraskAntenna.jpg I feed it 15 volts on the twinax pair, pull that out of the toroids centertap, regulated it with a 12V 3-terminal. You can see the prototype in the top right corner. -- 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? (fwd)
gary schrieb: Just meditating out loud, if you were to go push pull with a ferrite antenna AND you are winding it yourself, you could avoid the biasing resistors by putting a center tap in the antenna itself, then tie that center tap to an appropriate bias voltage. I haven't seen this done, so their may be a gotcha with that scheme, but the science is good. Works with SA602. A russian web-site shows differential turns on a ferrite rod. tested Generally you will get a lower noise circuit if the input device is an amplifier rather than a buffer. Yep. Lanksford's input stage is essentially a push pull buffer, but I don't see that cancelling 2nd harmonics like a push pull amp. But for a whip, which is a single ended input, I don't see a way to get a differential input. Not true for a ferrite antenna. You can transformer couple the input. Then the whip is at DC and it is possible to let DC-current to ground. tested - Henry -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
Poul-Henning Kamp schrieb: In message 4f64f279.4040...@arcor.de, ehydra writes: Marek Peca schrieb: This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. If you make the antenna about 10x bigger you can omit the whole ferrite. I have used two antennas, an unloade air-coil, actually plastic-lid-coil: http://phk.freebsd.dk/loran-c/Antenna/ Yeah. I remember the red. The degaussing coil of old TVs can work. Some resonate at 50KHz which is a little low but it depends on the manufacturer. So try it. and a vertical monopole based on a Chris Trask design I can highly recommend: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf In my implementation, it covered DC to 200MHz until I low-pass'ed it. His designs are always a good source but this one is AC-coupled ;-) A CD4069 is all one needs for first experiments. I was satisfied. - Henry -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
In message 4f65d971.8070...@arcor.de, ehydra writes: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf In my implementation, it covered DC to 200MHz until I low-pass'ed it. His designs are always a good source but this one is AC-coupled ;-) Not in my implementation, I have eliminated the input capacitor because the active element is 3cm from the PCB, and I drive the output with a centertapped transformer. -- 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? (fwd)
I wonder because ALL of the shown circuits in his pdf are AC-coupled. It is maybe possible to servo-loop with OpAmps but surely not worth the effort. Useful too as a Scope FET-probe. - Henry Poul-Henning Kamp schrieb: In message 4f65d971.8070...@arcor.de, ehydra writes: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf In my implementation, it covered DC to 200MHz until I low-pass'ed it. His designs are always a good source but this one is AC-coupled ;-) Not in my implementation, I have eliminated the input capacitor because the active element is 3cm from the PCB, and I drive the output with a centertapped transformer. -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
On Sun, 18 Mar 2012 13:25:54 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 4f65d971.8070...@arcor.de, ehydra writes: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf In my implementation, it covered DC to 200MHz until I low-pass'ed it. His designs are always a good source but this one is AC-coupled ;-) Not in my implementation, I have eliminated the input capacitor because the active element is 3cm from the PCB, Could you explain how the distance of the antenna to the PCB is related to a DC block capacitor? And how do you block current flowing from the input stage of your amplifier into the antenna? and I drive the output with a centertapped transformer. Do you really mean a transformer? Or just a center tapped inductor? And how does that fit into the biasing? Or does your circuit contain more elements at the output than a transfomer/inductor and the biasing resistor? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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)
The circuit in question doesn't appear to be in the PDF. You need to use a lot of caution with Lankford's theories. I don't want to get into a pissing contest, so I will leave it at that. Push pull with transformers goes back to the tube days. It is a convenient scheme to kill 2nd harmonic distortion while at the same time biasing the single sex amplifier. Take the center tap and tie it to a positive voltage. Feed the other two inputs to the transformer with a differential signal. You have blocked DC from the output, restoring a ground referenced single phase. (as opposed to differential) output. These active whips are prone to picking up electrical noise. Fine if you live in the boonies. Not so good for urban dwellers. If the antenna is just a wire in the air, I'm not sure what good it does to capacitively couple the input. Who cares if some DC is floating on a wire just poking in the air. While some people think of transformers are bandlimiting devices, note that all those coupling caps have series inductance. There is no free lunch. Just meditating out loud, if you were to go push pull with a ferrite antenna AND you are winding it yourself, you could avoid the biasing resistors by putting a center tap in the antenna itself, then tie that center tap to an appropriate bias voltage. I haven't seen this done, so their may be a gotcha with that scheme, but the science is good. Generally you will get a lower noise circuit if the input device is an amplifier rather than a buffer. Lanksford's input stage is essentially a push pull buffer, but I don't see that cancelling 2nd harmonics like a push pull amp. But for a whip, which is a single ended input, I don't see a way to get a differential input. Not true for a ferrite antenna. ___ 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)
My choice would be a center tapped, shielded, air core loop, running into a low noise instrumentation amp. Center tap of loop to twinax shield, grounded at preamp. The instrumentation amp has fixed gain, and very high CMRR and PSRR. It also does the differential to single ended conversion properly and has a low output impedance. I have used an instrumentation amp in my breadboard, however, without center tapping and shielding. But it seemed to me to be a very good component for such low frequencies. 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? (fwd)
ehydra wrote: I wonder because ALL of the shown circuits in his pdf are AC-coupled. It is maybe possible to servo-loop with OpAmps but surely not worth the effort. Useful too as a Scope FET-probe. Not really the gain inaccuracy is somewhat excessive. One can do much better with the right circuit. The AC coupling between input and output stages isnt actually necessary if the output stage is biased appropriately. A higher supply voltage also helps. - Henry Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
In message 20120318182440.7cb729c2b018b0b2ca5f9...@kinali.ch, Attila Kinali w rites: On Sun, 18 Mar 2012 13:25:54 + Not in my implementation, I have eliminated the input capacitor because the active element is 3cm from the PCB, Could you explain how the distance of the antenna to the PCB is related to a DC block capacitor? And how do you block current flowing from the input stage of your amplifier into the antenna? The input to the amplifier is just a piece of metal, there is no need for a capacitor in series with it. The output from the amplifier goes to a transformer which drives a piece of twin-ax cable back to my lab. The reason for the transformer is that to go really deep in frequency the usual choke to separate the DC supply from RF signal doesn't work. I the 'cable-side' of the transformer, in both ends, is centertapped and that's how I provide power to the antenna. I have successfully received the Russian Omega-like system at 9-15 kHz and I have detected but not demodulated the 86Hz submarine transmission. That's DC enough for me :-) -- 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?
I was not concerned about processing power on a PC (or Mac for that matter) but for the uC that was used in PHK's project. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Chris Albertson albertson.ch...@gmail.com Sender: time-nuts-boun...@febo.com Date: Thu, 15 Mar 2012 15:48:41 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: 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. ___ 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)
DC in a transformer raises the low frequency corner a bit. Obviously not a problem in your case. I should point out that every active device Lankford puts in the signal chain adds noise since the amp is really just a buffer, not an amplifier. You really want front end gain so that devices after the gain stage do not add as much to the noise floor. It is input referred noise that is significant, and Lankford's design is terrible in this respect. Oops, I almost started that pissing contest. ;-) On 3/18/2012 11:44 AM, Poul-Henning Kamp wrote: In message20120318182440.7cb729c2b018b0b2ca5f9...@kinali.ch, Attila Kinali w rites: On Sun, 18 Mar 2012 13:25:54 + Not in my implementation, I have eliminated the input capacitor because the active element is 3cm from the PCB, Could you explain how the distance of the antenna to the PCB is related to a DC block capacitor? And how do you block current flowing from the input stage of your amplifier into the antenna? The input to the amplifier is just a piece of metal, there is no need for a capacitor in series with it. The output from the amplifier goes to a transformer which drives a piece of twin-ax cable back to my lab. The reason for the transformer is that to go really deep in frequency the usual choke to separate the DC supply from RF signal doesn't work. I the 'cable-side' of the transformer, in both ends, is centertapped and that's how I provide power to the antenna. I have successfully received the Russian Omega-like system at 9-15 kHz and I have detected but not demodulated the 86Hz submarine transmission. That's DC enough for me :-) ___ 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?
So, I just recently started trying to resurrect a Spectracom 8160A reference oscillator. I'm assuming this is proposed WWVB change going to bite me in the butt on this project as well. Not sure how it differs from units like the HP 117, but my understanding is that most of the old VLF receivers work about the same. Do I understand this correctly? I'm kind of new to all this. Jeez, what a time to get back in a hobby. Michael - KA7ZNZ ___ 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.4.64.1203170042050.2576@tesla, Marek Peca writes: My only argument against your versatile and well-performing solution is that it is a little bit overkill. As if running a handfull precision oscillators just for fun isn't overkill also ? :-) In other words, it would be certainly better to buy USRP N210, Actually that would be a very idea, because you cannot get rid of the down-sampler in the USRP and that would make Loran-C reception very tricky to implement. My point is to do something with relevant performance wrt. 10kHz wide LF signals. The crucial question is if your are doing timenuttery or radionuttery. If you are doing timenuttery, you want you ADC synchronized to your OCXO/Rb/Cs or whatever you have, and you don't want to have to deal with getting your IF frequency locked too. Soundcards use inconvenient frequencies and are seldom built to take an external clock signal. The useful bandwidth of LF to HF radio is about 9kHz, You need more than 25kHz for good Loran-C -- 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? (fwd)
Moin! On Fri, 16 Mar 2012 13:45:04 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: Hmm.. i someday have to look for a good introdcution into this stuff that doesn't rely on a lot of math. All the books i have rely at least on Laplace.. often on z-transformation as well. And that math isn't high school level anymore. This one isn't half bad: http://www.dspguide.com/ Juup, that one looks nice. Thanks! Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 Fri, 16 Mar 2012 20:02:27 -0700 gary li...@lazygranch.com wrote: I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. I'm not the one who wrote this, but it is true :-) Any filter has its phase dependend on the frequency. As a rule of thumb: the higher order the filter, the faster the phase changes. As long as you just do straight filtering, with no feed back, you care seldom about the phase. It's the amplitude of the signal you are interested in. But if you now go time nuttery, phase change means delay. And you dont know how large it exactly is, because you dont know where exactly the resonance frequency of the filter is. And more importantly, you cannot say how it changes over time (tempeture dependece, aging, etc). That said, i think this can be ignored for all practical purposes in an VLF receiver, as the enviromental changes in the atmospheric signal path are much larger than the small error you get from the filter. But then again, time nuts are time nuts ;) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 20120317104723.8c1832454f14a3f91a4fb...@kinali.ch, Attila Kinali w rites: That said, i think this can be ignored for all practical purposes in an VLF receiver, as the enviromental changes in the atmospheric signal path are much larger than the small error you get from the filter. But then again, time nuts are time nuts ;) Again: it most certainly can not be ignored for Loran-C -- 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? (fwd)
On Sat, 17 Mar 2012 10:01:13 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: That said, i think this can be ignored for all practical purposes in an VLF receiver, as the enviromental changes in the atmospheric signal path are much larger than the small error you get from the filter. But then again, time nuts are time nuts ;) Again: it most certainly can not be ignored for Loran-C Could you explain why? Yes, you need a higher BW for Loran-C, but the phase(f) function will give you only a distortion of the signal and a constant time delay in your signal recovery. But that shouldnt degrade the usefullness of the system. What am i missing here? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 2012031719.9536107ebf82050fe14ee...@kinali.ch, Attila Kinali w rites: On Sat, 17 Mar 2012 10:01:13 + Could you explain why? Yes, you need a higher BW for Loran-C, but the phase(f) function will give you only a distortion of the signal and a constant time delay in your signal recovery. But that shouldnt degrade the usefullness of the system. What am i missing here? Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. The more you disturb a Loran-C pulse, the more it just looks like a bit of a sine-function, and the harder it is to lock on the right zero-crossing. -- 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? (fwd)
I've designed filters for datacom chips. I know filtering. My point is the original author is making some assumptions in the design which are not stated. What I don't have a lot of hands on experience is with open circuit magnetics. (I do with closed circuit magnetics.) But I claim if the ferrite rod antenna is not capacitively loaded to resonate at the comm frequency, then there isn't significant group delay error. The antenna will have a natural resonant frequency comprised of the inductance and parasitic capacitance. But this represents an upper frequency limit. So simply operate below resonance and the group delay error is minimized. Filtering can be done following the preamp that connects to the antenna, and thus will not interact with it. -Original Message- From: Attila Kinali att...@kinali.ch Sender: time-nuts-boun...@febo.com Date: Sat, 17 Mar 2012 10:47:23 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) On Fri, 16 Mar 2012 20:02:27 -0700 gary li...@lazygranch.com wrote: I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. I'm not the one who wrote this, but it is true :-) Any filter has its phase dependend on the frequency. As a rule of thumb: the higher order the filter, the faster the phase changes. As long as you just do straight filtering, with no feed back, you care seldom about the phase. It's the amplitude of the signal you are interested in. But if you now go time nuttery, phase change means delay. And you dont know how large it exactly is, because you dont know where exactly the resonance frequency of the filter is. And more importantly, you cannot say how it changes over time (tempeture dependece, aging, etc). That said, i think this can be ignored for all practical purposes in an VLF receiver, as the enviromental changes in the atmospheric signal path are much larger than the small error you get from the filter. But then again, time nuts are time nuts ;) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 Sat, 17 Mar 2012 10:15:17 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 2012031719.9536107ebf82050fe14ee...@kinali.ch, Attila Kinali w rites: On Sat, 17 Mar 2012 10:01:13 + Could you explain why? Yes, you need a higher BW for Loran-C, but the phase(f) function will give you only a distortion of the signal and a constant time delay in your signal recovery. But that shouldnt degrade the usefullness of the system. What am i missing here? Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. The more you disturb a Loran-C pulse, the more it just looks like a bit of a sine-function, and the harder it is to lock on the right zero-crossing. Ah.. so it is because Loran-C uses the third zero crossing as specified measurement point, which you thus have to capture with the greates possible resolution. Am i right that for DCF77, WWVB and the like, where there is no such requirement on the zero crossing of a pulse, one can just lock to the carrier and the distortions from filters are not so relevant? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 Sat, 17 Mar 2012 10:27:03 + li...@lazygranch.com wrote: What I don't have a lot of hands on experience is with open circuit magnetics. (I do with closed circuit magnetics.) But I claim if the ferrite rod antenna is not capacitively loaded to resonate at the comm frequency, then there isn't significant group delay error. Ah.. you have here a wrong assumption. Normal antennas are resonant at the wanted frequency. This is in order to get maximum gain i the first stage (not to mention that the antenna is the only amplifier with no noise). Also all DCF77 antennas i have seen so far are ferrit rods with an attached capacitor, to form a resonant antenna. I think, it would be possible to use a non-resonant antenna. I don't know what the total noise would then be. But it would definitly be interesting to know whether a non-resonant antenna design would be better or worse. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 Sat, 17 Mar 2012 10:15:17 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. BTW: how do you compensate for the filter characteristics of your magnetic loop antenna? Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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)
Any filter's group delay can be equalized by all pass filters. Delay builds up at the filter corner. Since everything in the real world is causal, you add delay outside that corner frequency but in the passband to equalize it. This is to say, you can't remove delay, but just add it to flatten out the group delay. On 3/17/2012 5:44 AM, Attila Kinali wrote: On Sat, 17 Mar 2012 10:15:17 + Poul-Henning Kampp...@phk.freebsd.dk wrote: Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. BTW: how do you compensate for the filter characteristics of your magnetic loop antenna? 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] WWVB BPSK Receiver Project? (fwd)
Hello, gary, I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. It was me, a time-nuts newbie. My previous related posts were: http://www.febo.com/pipermail/time-nuts/2012-March/065049.html http://www.febo.com/pipermail/time-nuts/2012-March/065003.html http://www.febo.com/pipermail/time-nuts/2012-March/065009.html etc. and http://www.febo.com/pipermail/time-nuts/2012-March/065135.html The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. Let me clarify the unclear statement. I was reacting to Poul-Henning Kamp's (true) statement, that: 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. In my design, I have used a ferrite rod LC circuit as and antenna and also the only element of selectivity in front of sampling. So, there was a 2nd order only filter. The useful signal of DCF77 (afaik yout WWVB is very similar now with BPSK) spans over ~1kHz. In my design, in contrast to P.-H. K.'s approach, I use only ~40ksps, so the 2nd order ferrite rod circuit should pass 1kHz, but it should attenuate somewhere around +-10..20kHz. I.e., the result will be always a compromise. Unfortunately, I don't have a measurement of my worked circuit's Q, but let us assume Q=20..100 can be realistic value for ferrite rods. Then, the filter's BW will be somewhere 0.8..4kHz, what means, that its phase over the interesting 1kHz band will _not_ be straight line, but somewhat curved. This is the only thing about ferrite rod and phase I meant. To conclude, I would like to repeat, that in my oppinion the ferrite rod is easy and common antenna for LF signals, so that in such a case the phase will be curved anyway. Of course you can feed the P.-H. K.'s 1Msps input by more wide-band antenna, not the ferrite rod, to get more linear phase without SW compensation. Greeting from 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? (fwd)
On Sat, 17 Mar 2012 06:13:28 -0700 gary li...@lazygranch.com wrote: On 3/17/2012 5:44 AM, Attila Kinali wrote: On Sat, 17 Mar 2012 10:15:17 + Poul-Henning Kampp...@phk.freebsd.dk wrote: Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. BTW: how do you compensate for the filter characteristics of your magnetic loop antenna? Any filter's group delay can be equalized by all pass filters. Delay builds up at the filter corner. Since everything in the real world is causal, you add delay outside that corner frequency but in the passband to equalize it. This is to say, you can't remove delay, but just add it to flatten out the group delay. Sorry, i asked in a misleading way. I didnt mean to ask what technique to use to flaten the phase delay, but rather how does phk know how the compensating filter should look like? For this, one needs to exactly characterize the antenna-amplifier chain...AFAIK Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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)
Dear Poul-Henning, My only argument against your versatile and well-performing solution is that it is a little bit overkill. As if running a handfull precision oscillators just for fun isn't overkill also ? :-) I don't know -- are there any limits for the fun in a time-nut sense? :-) I hope not. The point is, with which kind of toy we would like to play. In other words, it would be certainly better to buy USRP N210, Actually that would be a very idea, because you cannot get rid of the down-sampler in the USRP and that would make Loran-C reception very tricky to implement. Are you sure there are such a limitations? I must reveal, that I have not even once played with USRP N210, but I hope it does not have any BW limitations up to the Gig-Eth speed. Anyway, it would be an expensive and heavy receiver for LF-only signals. My point is to do something with relevant performance wrt. 10kHz wide LF signals. The crucial question is if your are doing timenuttery or radionuttery. If you are doing timenuttery, you want you ADC synchronized to your OCXO/Rb/Cs or whatever you have, Yes, I would like to have an option of external frequency standard. However, I would like to lock ordinary onboard quartz too, since many people without Rb (though they are pretty cheap these days) may use it as a disciplined frequency source, too. I mean no time-nuts, but ordinary hobbyists, going to tune their filters etc. Or people, wanting some time signal in place of poor GNSS reception without good NTP access (I know such a set i almost empty :-)). and you don't want to have to deal with getting your IF frequency locked too. Soundcards use inconvenient frequencies and are seldom built to take an external clock signal. So this is why I would like to supply a little bit tweaked sound card, tailored to receive LF-HF band signals up to say 10..20kHz of width. The useful bandwidth of LF to HF radio is about 9kHz, You need more than 25kHz for good Loran-C OK, thank you for this notice. I have not yet thinked about Loran, so I must look in more detail on it. 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? (fwd)
I've designed filters for datacom chips. I know filtering. My point is the original author is making some assumptions in the design which are not stated. Yes, my fault, I didn't write it properly, so by a ferrite rod in context of DCF/WWVB reception, I meand a ferrite antenna in an LC tuned circuit. Apologies for all who have been confused. What I don't have a lot of hands on experience is with open circuit magnetics. (I do with closed circuit magnetics.) But I claim if the ferrite rod antenna is not capacitively loaded to resonate at the comm frequency, then there isn't significant group delay error. Yes, see above. I meant an LC circuit, containing the ferrite rod antenna as the L. The antenna will have a natural resonant frequency comprised of the inductance and parasitic capacitance. But this represents an upper frequency limit. So simply operate below resonance and the group delay error is minimized. Filtering can be done following the preamp that connects to the antenna, and thus will not interact with it. Thank you for your understanding. 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? (fwd)
Any filter's group delay can be equalized by all pass filters. Delay builds up at the filter corner. Since everything in the real world is causal, you add delay outside that corner frequency but in the passband to equalize it. This is to say, you can't remove delay, but just add it to flatten out the group delay. Yes, the compensation can be made and it has been also pointed out in the first comment by Poul-Henning. The only remaining question is, how stable are the analogue filter parameters over time, to be compensated by fixed digital filter. It seems to me, that some very small phase errors produced by such a filter-filter mismatch may be acceptable. At least for low-cost device which I would like to rebuild and offer for WWVB audience (which is not present in our land). 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? (fwd)
Which basically matched my assumption. If the inductor is loaded, you have a narrowband filter. So again, this does not imply that a ferrite rod antenna per se has phase distortion. It is the LC filter than effects the group delay. On 3/17/2012 6:19 AM, Marek Peca wrote: Hello, gary, I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. It was me, a time-nuts newbie. My previous related posts were: http://www.febo.com/pipermail/time-nuts/2012-March/065049.html http://www.febo.com/pipermail/time-nuts/2012-March/065003.html http://www.febo.com/pipermail/time-nuts/2012-March/065009.html etc. and http://www.febo.com/pipermail/time-nuts/2012-March/065135.html The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. Let me clarify the unclear statement. I was reacting to Poul-Henning Kamp's (true) statement, that: 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. In my design, I have used a ferrite rod LC circuit as and antenna and also the only element of selectivity in front of sampling. So, there was a 2nd order only filter. The useful signal of DCF77 (afaik yout WWVB is very similar now with BPSK) spans over ~1kHz. In my design, in contrast to P.-H. K.'s approach, I use only ~40ksps, so the 2nd order ferrite rod circuit should pass 1kHz, but it should attenuate somewhere around +-10..20kHz. I.e., the result will be always a compromise. Unfortunately, I don't have a measurement of my worked circuit's Q, but let us assume Q=20..100 can be realistic value for ferrite rods. Then, the filter's BW will be somewhere 0.8..4kHz, what means, that its phase over the interesting 1kHz band will _not_ be straight line, but somewhat curved. This is the only thing about ferrite rod and phase I meant. To conclude, I would like to repeat, that in my oppinion the ferrite rod is easy and common antenna for LF signals, so that in such a case the phase will be curved anyway. Of course you can feed the P.-H. K.'s 1Msps input by more wide-band antenna, not the ferrite rod, to get more linear phase without SW compensation. Greeting from 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. ___ 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)
Yes, in order to equalize group delay, you need to know what to equalize. But with an educated guess as to the system response, he could get close. All this said, in 2012, I would rather the amplifier be simple gain, the inductor not loaded with capacitance and the filtering done past the amplifier. We aren't living in the era of 3 transistor circuits. When delta-sigma converters came on the scene. I wisely found new design skills. [They replaced much analog filtering.] So better just to do the filtering in DSP IF there is no critical power budget. On 3/17/2012 6:25 AM, Attila Kinali wrote: On Sat, 17 Mar 2012 06:13:28 -0700 garyli...@lazygranch.com wrote: On 3/17/2012 5:44 AM, Attila Kinali wrote: On Sat, 17 Mar 2012 10:15:17 + Poul-Henning Kampp...@phk.freebsd.dk wrote: Either you need to characterize the exact behaviour of your filter and build the necessary compensation for its phase/frequency behaviour into your receiver, or you need a very flat filter (both freq+phase) in order to reliably recognize the proper zero-crossing to track. BTW: how do you compensate for the filter characteristics of your magnetic loop antenna? Any filter's group delay can be equalized by all pass filters. Delay builds up at the filter corner. Since everything in the real world is causal, you add delay outside that corner frequency but in the passband to equalize it. This is to say, you can't remove delay, but just add it to flatten out the group delay. Sorry, i asked in a misleading way. I didnt mean to ask what technique to use to flaten the phase delay, but rather how does phk know how the compensating filter should look like? For this, one needs to exactly characterize the antenna-amplifier chain...AFAIK 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] WWVB BPSK Receiver Project? (fwd)
Which basically matched my assumption. If the inductor is loaded, you have a narrowband filter. So again, this does not imply that a ferrite rod antenna per se has phase distortion. It is the LC filter than effects the group delay. Yes, exactly. Excuse my loose speech before not explicitly mentioning LC tuned circuit. 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? (fwd)
Hi The problem with delay compensation in a Time Nut environment is that to do it you add delay. Your all pass network adds enough delay to the fast part of the passband to make it come out the same as the slow part. In real circuits you inevitably add some delay everywhere with the all pass, so the net is somewhat higher delay everywhere than the worst of the original filter. So far no problem. Change temperature or let things age and all those delays change. Since they are a sum of many things, they likely change in a complicated fashion. Change in delay is change in time. That is a Time Nut problem. Bob On Mar 17, 2012, at 9:40 AM, gary li...@lazygranch.com wrote: Which basically matched my assumption. If the inductor is loaded, you have a narrowband filter. So again, this does not imply that a ferrite rod antenna per se has phase distortion. It is the LC filter than effects the group delay. On 3/17/2012 6:19 AM, Marek Peca wrote: Hello, gary, I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. It was me, a time-nuts newbie. My previous related posts were: http://www.febo.com/pipermail/time-nuts/2012-March/065049.html http://www.febo.com/pipermail/time-nuts/2012-March/065003.html http://www.febo.com/pipermail/time-nuts/2012-March/065009.html etc. and http://www.febo.com/pipermail/time-nuts/2012-March/065135.html The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. Let me clarify the unclear statement. I was reacting to Poul-Henning Kamp's (true) statement, that: 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. In my design, I have used a ferrite rod LC circuit as and antenna and also the only element of selectivity in front of sampling. So, there was a 2nd order only filter. The useful signal of DCF77 (afaik yout WWVB is very similar now with BPSK) spans over ~1kHz. In my design, in contrast to P.-H. K.'s approach, I use only ~40ksps, so the 2nd order ferrite rod circuit should pass 1kHz, but it should attenuate somewhere around +-10..20kHz. I.e., the result will be always a compromise. Unfortunately, I don't have a measurement of my worked circuit's Q, but let us assume Q=20..100 can be realistic value for ferrite rods. Then, the filter's BW will be somewhere 0.8..4kHz, what means, that its phase over the interesting 1kHz band will _not_ be straight line, but somewhat curved. This is the only thing about ferrite rod and phase I meant. To conclude, I would like to repeat, that in my oppinion the ferrite rod is easy and common antenna for LF signals, so that in such a case the phase will be curved anyway. Of course you can feed the P.-H. K.'s 1Msps input by more wide-band antenna, not the ferrite rod, to get more linear phase without SW compensation. Greeting from 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. ___ 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)
Yes, in order to equalize group delay, you need to know what to equalize. But with an educated guess as to the system response, he could get close. All this said, in 2012, I would rather the amplifier be simple gain, the inductor not loaded with capacitance and the filtering done past the amplifier. We aren't living in the era of 3 transistor circuits. When delta-sigma converters came on the scene. I wisely found new design skills. [They replaced much analog filtering.] So better just to do the filtering in DSP IF there is no critical power budget. This may not be true, if you have some strong interference at the ferrite rod input. Of course, if it would be strong and near the signal frequency, it will not be attenuated much even by the 2nd order LC circuit, indeed. However, for f0=77.5kHz and B=1kHz, the LC circuit with Q=40 gives phase error over specified bandwidth about +-0.5deg p-p. Does such a phase non-linearity bother you? 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? (fwd)
I think the tempco of the ferrite is more significant than drift in the analog filter. Of course this again implies the better design is to not load the inductor with a cap, i.e. stay broadband, and then just filter post the preamp. The open circuit voltage will be lower without the resonant circuit. This is a case where the BF862 might do some good since the goal is to not load the inductor, either resistively or with capacitance. When you are dealing with components that are around 1nV/sqrt(hz), you can afford to throw some circuitry at the problem especially since the atmospheric noise will dominate. On 3/17/2012 6:38 AM, Marek Peca wrote: Any filter's group delay can be equalized by all pass filters. Delay builds up at the filter corner. Since everything in the real world is causal, you add delay outside that corner frequency but in the passband to equalize it. This is to say, you can't remove delay, but just add it to flatten out the group delay. Yes, the compensation can be made and it has been also pointed out in the first comment by Poul-Henning. The only remaining question is, how stable are the analogue filter parameters over time, to be compensated by fixed digital filter. It seems to me, that some very small phase errors produced by such a filter-filter mismatch may be acceptable. At least for low-cost device which I would like to rebuild and offer for WWVB audience (which is not present in our land). 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. ___ 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)
I think the tempco of the ferrite is more significant than drift in the analog filter. Perhaps I was unclear in this as well. I do not use nor plan to use any other filter than the (ferrite-L)-C resonant circuit itself. So, yes, the tempco of the ferrite makes its coefficients variation. The question is, whether phase errors 1deg p-p over 1kHz band are significant. 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? (fwd)
That would be 36ns group delay variation if I did the math correctly. However, what material are you using for the ferrite? The material can have a significant tempco. On 3/17/2012 7:17 AM, Marek Peca wrote: However, for f0=77.5kHz and B=1kHz, the LC circuit with Q=40 gives phase error over specified bandwidth about +-0.5deg p-p. Does such a phase non-linearity bother you? 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. ___ 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)
That would be 36ns group delay variation if I did the math correctly. OK And in article P. Hetzel: Time dissemination via the LF transmitter DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF Neuchatel, 1988., they conclude with timing results of about 2..10e-6 s RMS over ~1000km distance. However, I do not know what is the reality and whether such a performance is limited by atmosphere/ground conditions, or whether it could be better within LF band. However, what material are you using for the ferrite? The material can have a significant tempco. In my project, I have used noname rod taken from within DCF77 alarm clock. If I will recreate it, I will look for something defined at the store. 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? (fwd)
http://www.fair-rite.com/newfair/materials61.htm OK, assuming type 61, it is 0.1%/deg C. Let's go with +/- 5 degrees, which would be for indoor use. I don't have the equation handy for a damped LC. Certainly undamped would be worst case. f=1/(2*pi*sqrt(LC)). When the dust settles, the frequency shift is the square root of the temperature shift, so half a percent due to temperature ends up being a quarter percent frequency shift. ___ 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)
Hi Marek - I don't know where you are in CZ. I'm on the boarder in DE near PL and CZ. The distance to DCF77 is about 450km and if I check the amplitude across 24h I see considerable very deep fading effects! I think it is useless as a phase-coupled time receiver. At least in specific positions. It will loose phase at least for twice the day for approx. 2h ! That was the report for a ferrite rod. The other way would be a high-impedance FET-preamp vertical-wire antenna. I think this will resist much more fading effects. But it is unchecked at the moment. You're welcome to do it. The benefit of a resonated ferrite rod is the good bandpass filtering for local interferers like TV. The FET vertical wire will need heavily filtering thereafter. All in the whole dynamice range, of course. Ferrites can be temperature controlled. They have big spreads in parameters anyway! The production procedure is explained in the classical book about Ferrites: Snelling Soft Ferrites. - Henry Marek Peca schrieb: That would be 36ns group delay variation if I did the math correctly. OK And in article P. Hetzel: Time dissemination via the LF transmitter DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF Neuchatel, 1988., they conclude with timing results of about 2..10e-6 s RMS over ~1000km distance. However, I do not know what is the reality and whether such a performance is limited by atmosphere/ground conditions, or whether it could be better within LF band. However, what material are you using for the ferrite? The material can have a significant tempco. In my project, I have used noname rod taken from within DCF77 alarm clock. If I will recreate it, I will look for something defined at the store. -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
Dear Henry, I don't know where you are in CZ. I'm on the boarder in DE near PL and CZ. my former measurement (the one at YouTube, fairly good reception, winter) has been done under Erzgebirge, Teplice, CZ. Now I moved near Sumava (Boehmischer Wald), so tests may follow, if I will return to the topic. The distance to DCF77 is about 450km and if I check the amplitude across 24h I see considerable very deep fading effects! I think it is useless as a phase-coupled time receiver. At least in specific positions. It will loose phase at least for twice the day for approx. 2h ! That was the report for a ferrite rod. Thank you. The other way would be a high-impedance FET-preamp vertical-wire antenna. I think this will resist much more fading effects. But it is unchecked at the moment. You're welcome to do it. The benefit of a resonated ferrite rod is the good bandpass filtering for local interferers like TV. The FET vertical wire will need heavily filtering thereafter. All in the whole dynamice range, of course. This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. Ferrites can be temperature controlled. They have big spreads in parameters anyway! The production procedure is explained in the classical book about Ferrites: Snelling Soft Ferrites. Thank you for your pointer. Your idea of ferrite ovenization is cool. 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? (fwd)
The ferrite loop antenna receives the magnetic portion of the EM wave. It doesn't have to be a bandpass LC filter. The Wellbrook loop antennas are one example of a broadband antenna that receives the magnetic portion. -Original Message- From: ehydra ehy...@arcor.de Sender: time-nuts-boun...@febo.com Date: Sat, 17 Mar 2012 16:10:48 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: ehy...@arcor.de, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) Hi Marek - I don't know where you are in CZ. I'm on the boarder in DE near PL and CZ. The distance to DCF77 is about 450km and if I check the amplitude across 24h I see considerable very deep fading effects! I think it is useless as a phase-coupled time receiver. At least in specific positions. It will loose phase at least for twice the day for approx. 2h ! That was the report for a ferrite rod. The other way would be a high-impedance FET-preamp vertical-wire antenna. I think this will resist much more fading effects. But it is unchecked at the moment. You're welcome to do it. The benefit of a resonated ferrite rod is the good bandpass filtering for local interferers like TV. The FET vertical wire will need heavily filtering thereafter. All in the whole dynamice range, of course. Ferrites can be temperature controlled. They have big spreads in parameters anyway! The production procedure is explained in the classical book about Ferrites: Snelling Soft Ferrites. - Henry Marek Peca schrieb: That would be 36ns group delay variation if I did the math correctly. OK And in article P. Hetzel: Time dissemination via the LF transmitter DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF Neuchatel, 1988., they conclude with timing results of about 2..10e-6 s RMS over ~1000km distance. However, I do not know what is the reality and whether such a performance is limited by atmosphere/ground conditions, or whether it could be better within LF band. However, what material are you using for the ferrite? The material can have a significant tempco. In my project, I have used noname rod taken from within DCF77 alarm clock. If I will recreate it, I will look for something defined at the store. -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
gary wrote: OK, assuming type 61, it is 0.1%/deg C. IME, Type 78 is the usual choice for resonant antennas below 200 kHz (tempco of initial permeability = 1.0%/deg C). I have seen Type 33 used for broadband LF/MF antennas (tempco of initial permeability = 0.1%/deg C). Type 61 is generally not used below 200 kHz. 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] WWVB BPSK Receiver Project? (fwd)
Marek Peca schrieb: This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. If you make the antenna about 10x bigger you can omit the whole ferrite. The only benefit of a ferrite loaded coil is the size of it! In ancient time radios had flat air coils like spider webs. In fact they are named after spiders in german. This air coil can be resonated too! I can imagine a resonated vertical antenna. Never seen that but all it requires is a low impedance pre-amp stage and a loading coil of very high Q. - Henry -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
Check out Observations on Ferrite Rod Antennas, QEX, 2008. Type 61 works better at low frequencies regardless of manufacturers guidelines. -Original Message- From: Charles P. Steinmetz charles_steinm...@lavabit.com Sender: time-nuts-boun...@febo.com Date: Sat, 17 Mar 2012 12:01:36 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) gary wrote: OK, assuming type 61, it is 0.1%/deg C. IME, Type 78 is the usual choice for resonant antennas below 200 kHz (tempco of initial permeability = 1.0%/deg C). I have seen Type 33 used for broadband LF/MF antennas (tempco of initial permeability = 0.1%/deg C). Type 61 is generally not used below 200 kHz. 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. ___ 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)
Wouldn't the difference be directly proportional to the relative permeability? If so, the difference would be more like 125, not 10, depending on core material. -Original Message- From: ehydra ehy...@arcor.de Sender: time-nuts-boun...@febo.com Date: Sat, 17 Mar 2012 21:22:17 To: Marek Pecama...@duch.cz; Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: ehy...@arcor.de, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) Marek Peca schrieb: This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. If you make the antenna about 10x bigger you can omit the whole ferrite. The only benefit of a ferrite loaded coil is the size of it! In ancient time radios had flat air coils like spider webs. In fact they are named after spiders in german. This air coil can be resonated too! I can imagine a resonated vertical antenna. Never seen that but all it requires is a low impedance pre-amp stage and a loading coil of very high Q. - Henry -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
In the end every antenna receives the EM wave! The EM-wave is the far field. The antenna works in the near field where a dominant component can be the E or M. That depends on the antenna. Between the near and the far field the field is converted and local Z0 highly complicated. As far as I know every antenna declared as whole EM-capable wasn't it and I think it is maybe just impossible to couple directly EM to a antenna at least if the antenna should be engineered which means simple and cheap. The ferrite antenna couples the M component. The vertical capacitive antenna the E component! Both can be resonant or broadband. The ferrite antenna is highly nonlinear and therefor not suitable as transmitter. As we don't have a reverse component for FETs this is even true for the vertical capacitive antenna. And a wire antenna in the classical way is a M component antenna. No ferrites and low Z0 means it can be effectivly used as a transmitting device. - Henry li...@lazygranch.com schrieb: The ferrite loop antenna receives the magnetic portion of the EM wave. It doesn't have to be a bandpass LC filter. The Wellbrook loop antennas are one example of a broadband antenna that receives the magnetic portion. -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
Hi: The material permeability gets reduced to effective permeability depending on the rod length / diameter radio (you would like it to be = 100) to realize the material permeability). For example: http://www.magneticsgroup.com/pdf/erods.pdf More on ferrite loop sticks at: http://www.prc68.com/I/Loop.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html li...@lazygranch.com wrote: Wouldn't the difference be directly proportional to the relative permeability? If so, the difference would be more like 125, not 10, depending on core material. -Original Message- From: ehydraehy...@arcor.de Sender: time-nuts-boun...@febo.com Date: Sat, 17 Mar 2012 21:22:17 To: Marek Pecama...@duch.cz; Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: ehy...@arcor.de, Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) Marek Peca schrieb: This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. If you make the antenna about 10x bigger you can omit the whole ferrite. The only benefit of a ferrite loaded coil is the size of it! In ancient time radios had flat air coils like spider webs. In fact they are named after spiders in german. This air coil can be resonated too! I can imagine a resonated vertical antenna. Never seen that but all it requires is a low impedance pre-amp stage and a loading coil of very high Q. - Henry ___ 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)
No, there is a geometric saturation. You can't use the better permeability in reality. The optimum length to width relation is about 6 to 10 for ferrite rods. Here is a diagram: http://ehydra.dyndns.info/NG/time-nuts/Pettengill%20002.jpg This is one of the classics in my link list: http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html - Henry li...@lazygranch.com schrieb: Wouldn't the difference be directly proportional to the relative permeability? If so, the difference would be more like 125, not 10, depending on core material. -- ehydra.dyndns.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] WWVB BPSK Receiver Project? (fwd)
In message 4f64f279.4040...@arcor.de, ehydra writes: Marek Peca schrieb: This was almost the only reason for ferrite rod -- simplicity and attenuation of TVs, some LCDs, 50Hz etc. If you make the antenna about 10x bigger you can omit the whole ferrite. I have used two antennas, an unloade air-coil, actually plastic-lid-coil: http://phk.freebsd.dk/loran-c/Antenna/ and a vertical monopole based on a Chris Trask design I can highly recommend: http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf In my implementation, it covered DC to 200MHz until I low-pass'ed it. -- 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? (fwd)
In message 20120315234624.a2da94430a247d235ca68...@kinali.ch, Attila Kinali w rites: How good would that DAC need to be? Depends on the level of ambition ? 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. There is no problem running bare-metal on ARM9's, I've done it. But heck, it would be even better if you could load an OS on it, and still get your bits through. 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 ;-) Well, if you want to do full-FRI averaging for a loran-chain, you need something like 99600*2 * 4 = 800Kb. If you want to do the full-hour averaging the WWVB doc talks about or DCF77 full-second phase-code, you need 2 MB for just the buffer. 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. USB2, not USB3. -- 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?
In message CAL8XPmM+O0EP7yK7mUC16urmyBesWb+wR4UyJd5LrhLCSbWt=g...@mail.gmail.com , Azelio Boriani writes: 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 ... Yes. And once you have filled a few seconds into the buffer, you can multiply each of the 1000 locations with a n*sine and n*cosine, and sum the results and you have a phase vector for the signal at n KHz. For signals like DCF77 on half kHz grid, you need a 2 msec = 2000 samples long buffer. -- 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?
In message CABbxVHv0ZOmcwO6A1r8XRXjQ=v-rqw4dqorl9x8va1qxa0r...@mail.gmail.com , Chris Albertson writes: That would be big expensive filter. All you really need is the average of the last N samples. Expensive ? 2kB of memory ? Not even close to expensive. But with a 24b-t ADC you may not need AGC 16 bits has meant that I never needed AGC. -- 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?
In message cabbxvhvjaxnap-kzpn6xduwa22lbokffafh35m8u_fjuup4...@mail.gmail.com , Chris Albertson writes: But you are right in that using dttsp [...] GNU Radio If the objective here is time-nuttery, both of these are badly suited because they are built to extract the rapidly changing information, not for long averages of carrier phase. -- 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? (fwd)
Moin! On Fri, 16 Mar 2012 07:09:05 + Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315234624.a2da94430a247d235ca68...@kinali.ch, Attila Kinali writes: 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 ;-) Well, if you want to do full-FRI averaging for a loran-chain, you need something like 99600*2 * 4 = 800Kb. If you want to do the full-hour averaging the WWVB doc talks about or DCF77 full-second phase-code, you need 2 MB for just the buffer. Hmm... do you mean you want to store all samples of an hour and then avarage over it? I think it would be better to just store phase offset points for every second and then avarage over this. That would require much less storage. 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. USB2, not USB3. I'm not talking about SuperSpeed. USB2 support has been around for quite some time in ARM7 class uC. But USB2 does not mean you support a certain speed, just the data structures follow the revised standard. Yes, USB2 introduced the HighSpeed mode (the 480Mbit/s), but below ARM9/MIPS class CPUs it wasn't supported until about 2-3 years ago. AFAIK the Atmel SAM3U was one of the first Cortex-M3 with HighSpeed support available in volumes... and that was IIRC late 2009, early 2010. And the number of uC's with HighSpeed support isn't that large yet. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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 20120316085256.9e25deaeee4f7f8617989...@kinali.ch, Attila Kinali w rites: Hmm... do you mean you want to store all samples of an hour and then avarage over it? That would be the ideal way to do it, since it would make one heck of a comb filter and eliminate pretty much anything else. -- 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? (fwd)
p...@phk.freebsd.dk said: Hmm... do you mean you want to store all samples of an hour and then avarage over it? That would be the ideal way to do it, since it would make one heck of a comb filter and eliminate pretty much anything else. That only works if your reference clock is stable enough over the collecting period. I'm far from a DSP wizard. Assume I have a signal at 100 kHz with a bandwidth of 1 kHz. (or pick any numbers you like) How many samples per second do I need? How stable does my sampling clock need to be if I collect data for for N seconds? Is stable the right term? What's the right way to think about the question I'm trying to ask? -- These are my opinions, not necessarily my employer's. 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] WWVB BPSK Receiver Project? (fwd)
Hi Could you generate a lead and a lag estimate of the signal (in addition to your center) and integrate against each of them on the fly? If so you would need a *lot* less memory. I seem to recall you tried something like this on the one of the Loran receivers. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Friday, March 16, 2012 4:23 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) In message 20120316085256.9e25deaeee4f7f8617989...@kinali.ch, Attila Kinali w rites: Hmm... do you mean you want to store all samples of an hour and then avarage over it? That would be the ideal way to do it, since it would make one heck of a comb filter and eliminate pretty much anything else. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
In message b8fa03dc1dd84a588a317b314a6fc...@vectron.com, Bob Camp writes: Could you generate a lead and a lag estimate of the signal (in addition to your center) and integrate against each of them on the fly? If so you would need a *lot* less memory. I seem to recall you tried something like this on the one of the Loran receivers. The reason to use the lead/center/lag model, is that you have a moving signal you need to track, but for timenuts purposes the signal is not going to move more than a few microseconds over an hour, so it is probably a better strategy to just average the heck out of the signal. It is not even clear to me that the phase-coding helps frequency reception at all, I tried it with the very strong phase-coding of DCF77 and there was no statistical significance relative to heavy duty carrier averaging. But it clearly helps a lot with phase-determination, and for that lead/center/lag is the way to go, but you may still want to average for a minute, then resolve the phase using the phase-modulation, rather than run it in real-time. -- 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? (fwd)
On Fri, 16 Mar 2012 03:08:47 -0700 Hal Murray hmur...@megapathdsl.net wrote: p...@phk.freebsd.dk said: Hmm... do you mean you want to store all samples of an hour and then avarage over it? That would be the ideal way to do it, since it would make one heck of a comb filter and eliminate pretty much anything else. That only works if your reference clock is stable enough over the collecting period. Not necessarily. The noise of the VLF signal is much higher than the noise of your crystal, hence the limit will not be the stability of your crystal. Beside, integrating over such long periods tend to eliminate noise sources. I'm far from a DSP wizard. Assume I have a signal at 100 kHz with a bandwidth of 1 kHz. (or pick any numbers you like) How many samples per second do I need? How stable does my sampling clock need to be if I collect data for for N seconds? You need to get at least two times the bandwidth (Nyquist criterion). Ie in the example above a sampling rate above 2kHz would be enough. But: * you need to filter out all noise outside the band you are interested in, otherwise it gets folded in and degrades your SNR. * you need a low jitter ADC, as the jitter requirements are set by the signal frequency, not by the bandwidth. * the analog part from the input to the sample and hold circuit of the ADC need to be able to handle the high frequencies of your signal. Is stable the right term? What's the right way to think about the question I'm trying to ask? That i cannot say, as i dont know what you are asking :-) In this case, i think you are asking for phase noise as well as short term stability (tau averaging time) Calculating effects on signal processing in the precense of noise is nothing trivial. Dont worry if you dont understand everything on the spot or cannot form an intuitive understanding. Hmm.. i someday have to look for a good introdcution into this stuff that doesn't rely on a lot of math. All the books i have rely at least on Laplace.. often on z-transformation as well. And that math isn't high school level anymore. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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 20120316141539.d8305feaa33c99781667e...@kinali.ch, Attila Kinali w rites: Hmm.. i someday have to look for a good introdcution into this stuff that doesn't rely on a lot of math. All the books i have rely at least on Laplace.. often on z-transformation as well. And that math isn't high school level anymore. This one isn't half bad: http://www.dspguide.com/ -- 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? (fwd)
Hi One assumption is that you will indeed be capturing / averaging for several days. I'd include some sort of model for sunrise / sunset shifts (might be just ignore for the next hour). Another assumption is that your local reference is close enough and stable enough to make a multi day average meaningful. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Friday, March 16, 2012 9:03 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) In message b8fa03dc1dd84a588a317b314a6fc...@vectron.com, Bob Camp writes: Could you generate a lead and a lag estimate of the signal (in addition to your center) and integrate against each of them on the fly? If so you would need a *lot* less memory. I seem to recall you tried something like this on the one of the Loran receivers. The reason to use the lead/center/lag model, is that you have a moving signal you need to track, but for timenuts purposes the signal is not going to move more than a few microseconds over an hour, so it is probably a better strategy to just average the heck out of the signal. It is not even clear to me that the phase-coding helps frequency reception at all, I tried it with the very strong phase-coding of DCF77 and there was no statistical significance relative to heavy duty carrier averaging. But it clearly helps a lot with phase-determination, and for that lead/center/lag is the way to go, but you may still want to average for a minute, then resolve the phase using the phase-modulation, rather than run it in real-time. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
In message 34c510bb3c6449b89ac4f7fbc20f4...@vectron.com, Bob Camp writes: One assumption is that you will indeed be capturing / averaging for several days. I'd include some sort of model for sunrise / sunset shifts (might be just ignore for the next hour). Some of my best results had 8 buffers each used for 3 hours and all timenuttery based on 24 hour differences from these buffers. Another assumption is that your local reference is close enough and stable enough to make a multi day average meaningful. Well, the above technique got me a new offset estimate every three hours and that did a pretty good job on both OCXO and Rb disciplining. -- 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? (fwd)
Hi My main concern on short averages is the relatively long path from WWVB to most of the target audience. The day / night phase shift is fairly significant over a long path. That's something I would want to process out. Since it (hopefully) is predictable, it's just another thing to feed into the signal estimation side of the process. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Friday, March 16, 2012 12:27 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd) In message 34c510bb3c6449b89ac4f7fbc20f4...@vectron.com, Bob Camp writes: One assumption is that you will indeed be capturing / averaging for several days. I'd include some sort of model for sunrise / sunset shifts (might be just ignore for the next hour). Some of my best results had 8 buffers each used for 3 hours and all timenuttery based on 24 hour differences from these buffers. Another assumption is that your local reference is close enough and stable enough to make a multi day average meaningful. Well, the above technique got me a new offset estimate every three hours and that did a pretty good job on both OCXO and Rb disciplining. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
In message f8ac6c21eb1140b384332cb89b642...@vectron.com, Bob Camp writes: My main concern on short averages is the relatively long path from WWVB to most of the target audience. The day / night phase shift is fairly significant over a long path. So do I relative to DCF77 which I used for my experiments. The point about having 8 buffers per day is that you only compare 03:00-05:59 to 03:00-05:59 the previous or the next day, so the sun-effects almost entirely cancel out. -- 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? (fwd)
Bob, To address that diurnal phase issue, for fun, we could set up a cloud-based time-nuts WWVB common view network. With a couple of sites in each state, imagine the wonderful daily or hourly animated plots that would result. /tvb Hi My main concern on short averages is the relatively long path from WWVB to most of the target audience. The day / night phase shift is fairly significant over a long path. That's something I would want to process out. Since it (hopefully) is predictable, it's just another thing to feed into the signal estimation side of the process. Bob ___ 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 14 Mar, 2012, at 18:08 , Brooke Clarke wrote: 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. It is a little interesting that the PTTI paper left out some of the interesting details one would need to actually decode the new signal, in particular the specification of the 14 second Sync sequence, which is necessary to know to find the alignment of minutes, and the value of the 60-bit hour-synchronization code, which defines the sequence of phase reversals in each minute's modulation in an hour and, as I understand it, is necessary to know to take full advantage of the hour-averaging thing. I assume this might have been done to allow the company which participated in the design of the signal to complete a receiver for it before they start transmitting that way while keeping anyone else from starting a receiver project until after the transmissions start? Dennis Ferguson ___ 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)
Hello, thank you for your oppinion. On Thu, 15 Mar 2012, Poul-Henning Kamp wrote: 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. (..) You are right. I admit, that using comfortable oversampling, the converter is more versatile and analogue-side filters are absolutely non-critical ones. Nothing against that, moreover, I confess that I often use this approach, oversampling simple anti-aliasing, rather than converse. Now, I am still unsure whether to deploy the relatively cheap lower performance board with sampling in order of 40..80ksps. You are right, that 1Msps solves the task better or at least with the same performance. But, you pay few $ more (not so important), some few watts more and take more data before decimation (may be done in FPGA, of course). I know that USB2.0 handles 30MB/s on majority of HWOSes and you still need only about 2MB/s. My only argument against your versatile and well-performing solution is that it is a little bit overkill. In other words, it would be certainly better to buy USRP N210, then you may sample directly 0..250MHz @100Msps, and 1Gbps Ethernet is quite common these days, too. You have everything coded inside and its software support is also very good, including virtual soundcard connection etc. My point is to do something with relevant performance wrt. 10kHz wide LF signals. Well, I still think that 40..100ksps (1-2 inputs) module acting like a SAR sound-card may be usable as well as 1Msps for LF time-nuttery with a bare ferrite rod, and together with a mixer for DRM and Synchronous AM fans. The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. Well, I will wait for more reactions, till now I have 2 positive and 1 yours, discouraging from 40ksps approach. Thank you and please note my respect to your approach and achievements. 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? (fwd)
I lost track of who wrote this, but why is it assume a ferrite rod has non-linear phase. [Group delay error I presume). Now I assume this presumes the rod is used in a LC circuit, but if the Q is not high, the phase linearity won't necessarily be bad. Basically I'd like to hear more from whomever wrote this. The useful bandwidth of LF to HF radio is about 9kHz, DCF77-like standards with PRBS is about 1.5kHz. Of course the ferrite rod as an input filter *will* have a non-linear phase, but it still seems to me it is the simplest and most common receiptor for LF time signals. ___ 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 20120315043646.1bc3f11b...@karen.lavabit.com, Charles P. Steinmet z writes: 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. And isn't that what being a time-nut is all about ? VLF signals, once they have phase-code, are pretty good for frequency stabilization, you just need to use an averaging time of 24 hours. -- 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 Charles: There's another thing the WWVB ( WWV) do that GPS does not and that's Daylight Saving Time. Pop quiz. . . . what are the dates DST is turned on and off? http://en.wikipedia.org/wiki/Daylight_saving_time_around_the_world#United_States_of_America Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html Charles P. Steinmetz wrote: 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. ___ 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?
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. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, 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] WWVB BPSK Receiver Project?
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. I think the low transmitting-antenna bandwidth will prevent an unambiguous identification of the exact cycle of phase inversion, just as it smears out the AM transition from high power to low power. Fitting a model to the signal's AM exponential decay (or PM transition) would be better than a simple threshold, but at best it might get down to 50 us territory (excluding the propagation delay and iono uncertainties). Cheers, 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] 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. There would be an SNR penalty for this, though, called squaring loss. A PIC that knew when the transitions would happen and inverted the original signal would be free of squaring loss, since its reversing-signal would be noiseless. My worry, though, is that even this preprocessing doesn't look like it would give as good a signal as the original WWVB. Eyeballing the phase data derived from John Seamons' capture seems to show some phase variation from bit to bit, even those bits with the same nominal carrier phase. Some nonlinearity in the transmitter when hit with these phase transients perhaps. How quickly does it average out in a carrier-phase receiver? Unknown. Cheers, 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] WWVB BPSK Receiver Project?
Brooke wrote: There's another thing the WWVB ( WWV) do that GPS does not and that's Daylight Saving Time. Doesn't that reinforce my point? Automatic adjustment of time-of-day clocks for DST is not really a time nut priority, is it? Very convenient in daily life, yes -- but to the general public, time nuts included, not to time nuts qua time nuts. 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] WWVB BPSK Receiver Project?
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. That part of the paper bothered me. There's nothing preventing a receiver from averaging the current AM-only signal for a long time. They shouldn't be taking credit for that. A receiver capable of integrating over a few hours *using the existing signal* would arguably achieve many of the stated goals of the paper, including the jammer resistance. Maybe the new signal is an improvement, and I would have nothing against it if it doesn't hurt the overall phase stability, but apples should be compared with apples. Cheers, 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] WWVB BPSK Receiver Project?
How about this: Generate a precise 60 KHz signal from a GPSDO's 10 MHz. Modulate it with 1 bit audio generated by a Linux program which would know about DST. Feed this to a loop around the house to give a good 60 Khz signal inside but little outside. I have thought of this to keep my Atomic Clocks working :-) -- 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?
On Wed, 14 Mar 2012 18:14:56 -0700 WB6BNQ wb6...@cox.net wrote: 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. Could someone be so kind and could explain me what the problem with the BPSK modulation is? I mean the phase of WWVB shifts around several 10us during sunrise/sunset already... Not to talk about the changing propagation conditions. Just see [1] for an example of what's happening. Yes, for those devices that lock on the phase, you'd have to change their correction/detection loop, but overall, they should still work. Attila Kinali [1] http://www.febo.com/time-freq/wwvb/spectracom/index.html -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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 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. Unfortunately, this works only with a few types of sound cards. Last several years, most of PC audio cards use sigma-delta ADCs and there is no way to get quality undersampling. Tried it. I can not tell there was no signal -- there were really some carriers mirrors, but on odd frequencies and largely attenuated. Greetings, 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?
On 3/14/12 9:14 PM, J. Forster wrote: 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. Oh... I was assuming you had the two quadrature square waves (which are just like the saturated LO for the mixer in RF land) 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. Yes.. but if you don't care about the bitstream, and you want simpler hardware, squaring works. (especially if the modulator doesn't have good carrier suppression) ___ 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?
Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Poul-Henning Kamp p...@phk.freebsd.dk Sender: time-nuts-boun...@febo.com Date: Wed, 14 Mar 2012 22:16:38 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: 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. ___ 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, 15 Mar 2012 13:50:08 + shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I think Poul-Henning is refering to his AducLoran receiver, which used a 1Msps ADC [1]. I dont remember what he exactly does with the signal, but IIRC he uses a 40MHz uC which leaves him with 40 Cycles per sample, which is quite a lot if you only do just some math calculation to detect the start of a second... And unlike with the FPGA, it does not take more time to process 8bit or 24 bit samples as the uC works with 32bit numbers anyways. Attila Kinali [1] http://phk.freebsd.dk/AducLoran/ -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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 6:50 AM, shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. You could use an FPGA, but the data rate isn't all that high. The signal is fairly narrow band (1 kHz, I should think). What you might want to do is build a ADC/FPGA combo that provides a nice USB/Ethernet interface for the sample stream which has been digital downconverted and filtered. the FPGA takes care of the icky glue logic details and does a bit of decimation. ___ 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 american colleagues, as I read last few posts about WWVB, I am very tempted to return to LF time signal fun. As I wrote you, there vere very good results using cheap 2 IC circuitry and a PC with our local DCF77 signal. Under influence of this maillist, I am thinking about recreating of the receiver using recent MCU, ferrite rod on one side, optional 10MHz input, USB device acting as a standard USB audio class soundcard output. Everything working with GNUradio, MATLAB, HAM waterfalls etc. out of the box. Could be used as an audio frequency front-end for HAM radio, too. Would you be interested in such a kit? It should be $100 all inclusive, if there will be more people involved (let say 5-10) to cover PCBs. 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?
There are a number of sound cards (and have been for 10 years now) that can capture up to 95 KHz with extraordinary fidelity. They sample at 192 KHz and usually have 24 bit converters good tor 20+ bits. These can capture the complete FM MPX output pretty easily. Some of the newer ADC's have less that .001% THD at 192 KHz sampling. The AK5394a for example has -105 dB THD at 1 KHz. Can be had as a chip for about $22 ea if you want to build your own. Some current motherboards have an SPDIF input that can handle the 192 KHz sample rate. The next challenge is getting the OS to handle it, not difficult. Demian ___ 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?
Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. -John On Wed, 14 Mar 2012 18:14:56 -0700 WB6BNQ wb6...@cox.net wrote: 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. Could someone be so kind and could explain me what the problem with the BPSK modulation is? I mean the phase of WWVB shifts around several 10us during sunrise/sunset already... Not to talk about the changing propagation conditions. Just see [1] for an example of what's happening. Yes, for those devices that lock on the phase, you'd have to change their correction/detection loop, but overall, they should still work. Attila Kinali [1] http://www.febo.com/time-freq/wwvb/spectracom/index.html -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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?
Jim wrote: a square wave, multiplied by itself, has the same output as input. Oh... I was assuming you had the two quadrature square waves (which are just like the saturated LO for the mixer in RF land) You don't have two square waves in quadrature. You have the (amplified) signal from the antenna. A Costas Loop recovers the bit stream and the carrier frequency (from the local VCO) from a BPSK. It is self syncronizing. Yes.. but if you don't care about the bitstream, and you want simpler hardware, squaring works. (especially if the modulator doesn't have good carrier suppression) I think a better implementation would be: Analog multiplier Adaptive comparator (slice level = 1/2 P_P signal) Flip Flop Rabbit ears filter at 60 kHz -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. ___ 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 7:49 AM, J. Forster wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. and the cleverness of the Costas loop is that it uses (an estimate of) the current data bit (the output of the I arm) to flip the sign of the error signal from the quadrature arm. There's a lot of scope for modification of the basic linear Costas loop. Hard/soft limiters in either or both arms, you've got three filters (the two arm filters and the loop filter) to fool with, plus all sorts of schemes using data aiding where you get feedback from your symbol slicer to help do a better job on the carrier tracking. You can also run your loop with hard limited signal input (makes the mixers turn into XOR gates). If you don't need the bits in real time (i.e. you can tolerate some latency), then you can also build tracking loops that effectively look into the future; i.e. make decisions on carrier and bit at time t using future data from tnow, as well as t=[-infinity, now]. 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?
Why make it simple when complicated also works? -John On 3/15/12 7:49 AM, J. Forster wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. and the cleverness of the Costas loop is that it uses (an estimate of) the current data bit (the output of the I arm) to flip the sign of the error signal from the quadrature arm. There's a lot of scope for modification of the basic linear Costas loop. Hard/soft limiters in either or both arms, you've got three filters (the two arm filters and the loop filter) to fool with, plus all sorts of schemes using data aiding where you get feedback from your symbol slicer to help do a better job on the carrier tracking. You can also run your loop with hard limited signal input (makes the mixers turn into XOR gates). If you don't need the bits in real time (i.e. you can tolerate some latency), then you can also build tracking loops that effectively look into the future; i.e. make decisions on carrier and bit at time t using future data from tnow, as well as t=[-infinity, now]. 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.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, 15 Mar 2012 07:49:15 -0700 (PDT) J. Forster j...@quikus.com wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. That under the assumption, that they do not make sure that the average phase is zeros out (or converges to 90°). I have not found anything taht suggests this... on the other hand, there is nothing that suggests the contrary either. But you didnt address my main point yet: The phase of the WWVB signal is already fluctuating a lot, just by natural occuring atmospherical noise. If a 180° phase shift does destabilize your PLL, what does these shifts which are much larger do? Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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 If you can handle the data rates for Loran at 100 KHz with a micro, then you should be able to handle the data rates for something at 60 KHz. My guess is that a simple I know what the waveform is now compare it approach would not be terribly processor intensive. Put another way, you can easily predict exactly what the signal will be doing at any instant. You just need to steer to the error from that prediction. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali Sent: Thursday, March 15, 2012 10:26 AM To: shali...@gmail.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWVB BPSK Receiver Project? On Thu, 15 Mar 2012 13:50:08 + shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I think Poul-Henning is refering to his AducLoran receiver, which used a 1Msps ADC [1]. I dont remember what he exactly does with the signal, but IIRC he uses a 40MHz uC which leaves him with 40 Cycles per sample, which is quite a lot if you only do just some math calculation to detect the start of a second... And unlike with the FPGA, it does not take more time to process 8bit or 24 bit samples as the uC works with 32bit numbers anyways. Attila Kinali [1] http://phk.freebsd.dk/AducLoran/ -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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)
Forgot to Cc: the maillist, sorry. So, FYI: -- Forwarded message -- Date: Thu, 15 Mar 2012 16:31:14 +0100 (CET) From: Marek Peca ma...@duch.cz To: David J Taylor david-tay...@blueyonder.co.uk Subject: Re: [time-nuts] WWVB BPSK Receiver Project? Hello, I would perhaps be interested in something which would pick up our local 60 KHz transmissions, and having a USB interface would be OK. However, all my systems are Windows, so whatever software was produced would have to work on Windows. Of course I mean it should pick your 60kHz, as well as other systems known to me: Japanese 40kHz, 60kHz, Swiss 75kHz, British 60kHz and possibly others. Highly unsure about Russian 25kHz, even do not know, whether it is still on air. Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc. I take it that you are thinking of all the detection and processing in the PC? I would prefer as much processing as possible to be in the device, and that it perhaps output serial data over the USB port, looking like a GPS. Is that too much to ask? Well, I will tell you, what I would like to do in larger picture: 1. first, deliver simple USB audio sampling unit with 77.5kHz-proven ferrite rod preamplifier, ready to work with 40..80kHz signals at least; every processing within PC / Gnuradio framework; BUT 2. be ready to upgrade a firmware of the board to do all the PRBS BPSK tracking etc. within the board's MCU and deliver at least 1pps output, preferably also sinewave LF-locked output (range 100kHz..1MHz) for further processing. So, I mean, the board will work in PC-based SDR mode in first iteration, and after all the processing will be proven by multiple users, we can then switch to better firmware, which will do basic tasks even without the PC. I think I can provide basic firmware by myself, for more elaborate things it seems to me the best solution is to start our common open-source project. However, the board's MCU will accept anyone's firmware, anyway. Please, tell me your oppinion. I would like to know, whether to put some time into development, so if there are really some people, who would appreciate such a LF-SDR-USB kit. 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?
On Thu, Mar 15, 2012 at 1:48 AM, Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How about this: Generate a precise 60 KHz signal from a GPSDO's 10 MHz. Modulate it with 1 bit audio generated by a Linux program which would know about DST. The standard NTP source code distribution comes with a program to generate the time code. So you'd not have the write it yourself. It's purpose is to test the the WWV drivers n NTP. It is not built by default, from memory the source is in a directory called test. But for those radio clocks in your house the new WWVB signal should just work. They will not notice the phase modulation 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?
The major advantage of simply sampling at 192K is that it is so simple. Not much hardware outside of a good audio interface is required. But the mixer is attractive because then you can make it a quadrature mixer and then sample with both stereo channels. One then could use a more common 44.1 or 48K sample rate. You trade a bit of hardware up front for reduced processing requirements later. On Thu, Mar 15, 2012 at 12:38 AM, Peter Monta pmo...@gmail.com wrote: 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. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, 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. -- 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 Thu, 15 Mar 2012 20:02:31 +0100 (CET) Marek Peca ma...@duch.cz wrote: Of course I mean it should pick your 60kHz, as well as other systems known to me: Japanese 40kHz, 60kHz, Swiss 75kHz, British 60kHz and possibly others. Highly unsure about Russian 25kHz, even do not know, whether it is still on air. HBG has been switched of earlier this year. So DCF77 and Alison are the only time LF senders left in continental europe. 1. first, deliver simple USB audio sampling unit with 77.5kHz-proven ferrite rod preamplifier, ready to work with 40..80kHz signals at least; every processing within PC / Gnuradio framework; 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 :-) If i've time, i sketch the HW this weekend and build it as soon as i've time... And then it's just software :-) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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, 15 Mar 2012 22:51:55 +0100 Attila Kinali att...@kinali.ch wrote: Of course I mean it should pick your 60kHz, as well as other systems known to me: Japanese 40kHz, 60kHz, Swiss 75kHz, British 60kHz and possibly others. Highly unsure about Russian 25kHz, even do not know, whether it is still on air. HBG has been switched of earlier this year. So DCF77 and Alison are the only time LF senders left in continental europe. Err,, it's Allouis. Don't ask me where that Alison came from... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ 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 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.