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? (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? (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? (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? (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? (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? (fwd)
In message Pine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
On Thu, 15 Mar 2012 22:27:53 +
Poul-Henning Kamp p...@phk.freebsd.dk wrote:
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
How good would that DAC need to be?
1-4MB RAM
over a 256kB RAM it's get pretty thin if you want to stay in the uC
busines. Unless you want to use an ARM9 or better with external SDRAM
and Flash. But those are mostly BGA (very few QFP chips out there) and
they are assumed to run Linux or Windows CE on them... Support for bare
metal stuff is pretty thin.
On the other hand, if you dont have to support an OS and work on the
bare metal, you can get away with very little RAM. 128k is a damn lot
if you have to fill it with usefull data structures ;-)
USB2 interface
Which would mean you need a pretty recent chip as HighSpeed USB has not
been introduced into the uC world for more than 2 years or so.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
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Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
On 3/15/12 3:27 PM, Poul-Henning Kamp wrote:
In messagePine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
and if you have any sort of processing behind the 1MSPS, you can do a
simple digital filter and decimate.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
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