Re: [time-nuts] WWVB BPSK Receiver Project?
In message 20120315043646.1bc3f11b...@karen.lavabit.com, Charles P. Steinmet z writes: As others have pointed out, it isn't accurate enough for true time nut performance, and to get all of what it *is* capable of requires heroic efforts. And isn't that what being a time-nut is all about ? VLF signals, once they have phase-code, are pretty good for frequency stabilization, you just need to use an averaging time of 24 hours. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Hi Charles: There's another thing the WWVB ( WWV) do that GPS does not and that's Daylight Saving Time. Pop quiz. . . . what are the dates DST is turned on and off? http://en.wikipedia.org/wiki/Daylight_saving_time_around_the_world#United_States_of_America Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html Charles P. Steinmetz wrote: Bill wrote: [BPSK] leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold To be fair to NIST, there really aren't many people using WWVB as a source of laboratory-grade timing signals. As others have pointed out, it isn't accurate enough for true time nut performance, and to get all of what it *is* capable of requires heroic efforts. So in truth, the real market for WWVB is not time nuts -- it is people who want to know the time of day to within a second (the atomic clock crowd). And there are LOTS of them. So the change is likely to provide a modest upgrade path for the vast majority of actual users, at the expense of a few die-hards (hobbyists, mostly) who are trying to get more out of an LF timing source than it is really capable of delivering. From a public policy standpoint it seems to make good sense, however much it may offend time nuts' sensibilities. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
I'm not clear how accurately one can resolve the phase transition in the new scheme, but I suspect probably unambiguously to 1 cycle of the 60 KHz... and from there is merely a function of how accurately one can resolve the phase of the 60 KHz. This potentially can supply a much higher resolution time hack than the AM envelope. I think the low transmitting-antenna bandwidth will prevent an unambiguous identification of the exact cycle of phase inversion, just as it smears out the AM transition from high power to low power. Fitting a model to the signal's AM exponential decay (or PM transition) would be better than a simple threshold, but at best it might get down to 50 us territory (excluding the propagation delay and iono uncertainties). Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
In thinking about it a bit further, one might be able to take the 60 kHz received sine at some point in the receiver, full wave rectify and HP filter it (which doubles the frequency) then divide by two in a Flip-Flop and heavily filter the resultant. This is a hybrid solution... analog and digital... with not a uP in sight!! That would preserve the frequency, but ditch the phase reversals of the BPSK. Depending on the guts of the particular receiver, it might be possible to simply retrofit a PCB. There would be an SNR penalty for this, though, called squaring loss. A PIC that knew when the transitions would happen and inverted the original signal would be free of squaring loss, since its reversing-signal would be noiseless. My worry, though, is that even this preprocessing doesn't look like it would give as good a signal as the original WWVB. Eyeballing the phase data derived from John Seamons' capture seems to show some phase variation from bit to bit, even those bits with the same nominal carrier phase. Some nonlinearity in the transmitter when hit with these phase transients perhaps. How quickly does it average out in a carrier-phase receiver? Unknown. Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Brooke wrote: There's another thing the WWVB ( WWV) do that GPS does not and that's Daylight Saving Time. Doesn't that reinforce my point? Automatic adjustment of time-of-day clocks for DST is not really a time nut priority, is it? Very convenient in daily life, yes -- but to the general public, time nuts included, not to time nuts qua time nuts. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Part of the processing gain comes directly from the BPSK modulation and that amounts to a little over 10 dB improvement, but there's a further 18 dB gain to be had by accumulating an hours worth of data and processing that. That part of the paper bothered me. There's nothing preventing a receiver from averaging the current AM-only signal for a long time. They shouldn't be taking credit for that. A receiver capable of integrating over a few hours *using the existing signal* would arguably achieve many of the stated goals of the paper, including the jammer resistance. Maybe the new signal is an improvement, and I would have nothing against it if it doesn't hurt the overall phase stability, but apples should be compared with apples. Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
How about this: Generate a precise 60 KHz signal from a GPSDO's 10 MHz. Modulate it with 1 bit audio generated by a Linux program which would know about DST. Feed this to a loop around the house to give a good 60 Khz signal inside but little outside. I have thought of this to keep my Atomic Clocks working :-) -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] WWVB BPSK Receiver Project?
You are correct, however, I suppose you are using a loop antenna with a relatively high Q. The antenna gain is related to the Q when you have an antenna with a diameter much less than a wavelength. With a Q of 100 you would have a bandwidth of .6 kHz, If you go to say 20.kHz you would not need that high of a Q. Now, why do you need 1200 Hz bandwidth? Is it sending over 1kbaud data rate? I have not looked at the details. Just recall the data rate was 1 bit/second for time. 1200Hz at 60 kHz would represent a very low Q antenna only 5 or so. If you use CMOS switches you will still get aliasing at odd harmonics. So you would still need a front end filter. If you want a closer sampling frequency just make a simple frequency multiplier and you still can use the sound card output. The real point is where does SDR begin. As I said with CMOS switches you are effectively multiplying or mixing the incomming signal with square waves which have odd harmonics and you still get aliasing. 73 Bill wa4lav PS Just retired Friday. Maybe I will have some time to catch up with these discussions. Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Wed, 14 Mar 2012 18:14:56 -0700 WB6BNQ wb6...@cox.net wrote: His enthusiasm was aimed totally at new products. Although he admitted it leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold, he really did not seem to care. Pointing out that a failure with the GPS system left WWVB as the only alternate did not seem to matter either. Could someone be so kind and could explain me what the problem with the BPSK modulation is? I mean the phase of WWVB shifts around several 10us during sunrise/sunset already... Not to talk about the changing propagation conditions. Just see [1] for an example of what's happening. Yes, for those devices that lock on the phase, you'd have to change their correction/detection loop, but overall, they should still work. Attila Kinali [1] http://www.febo.com/time-freq/wwvb/spectracom/index.html -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] eLORAN and UrsaNav - GPS World
Article on the recent Loran testing. http://www.gpsworld.com/defense/eloran-and-ursanav-timing-everything-12744?u tm_source=GPSutm_medium=emailutm_campaign=Defense-PNT_03_14_2012utm_conte nt=eloran-and-ursanav-timing-everything-12744 Hope that link doesn't get truncated. Rob Kimberley ___ time-nuts mailing 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] broadband MPX signal stereo
Are you sure that a .WAV file can support the full MPX stereo and RDS signal? I suspect that you need raw samples that a sound card can't handle. The output of a FM stereo and RDS radio discriminator are beyond the usual audio bandwidth. The output of the discriminator full bandwidth is first used by the RDS decoder and then (partially filtered) by the stereo deMPX and then by the audio processor. On Thu, Mar 15, 2012 at 2:08 AM, ehydra ehy...@arcor.de wrote: Hi! I'm looking for a sampled wave-file from a radio receiver MPX-signal including the RDS frequency band around 57KHz. I searched the Net but found just nothing that worked. So I ask here. Maybe someone has the possibility to sample a couple of seconds. Thank you all! - 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?
I know I am not one of the good-ole-boys here but I'd say go 100% SDR with your PC without an external A/D converter. Ok, how would you do this? You use under sampling. Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. Unfortunately, this works only with a few types of sound cards. Last several years, most of PC audio cards use sigma-delta ADCs and there is no way to get quality undersampling. Tried it. I can not tell there was no signal -- there were really some carriers mirrors, but on odd frequencies and largely attenuated. Greetings, Marek ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] eLORAN and UrsaNav - GPS World
If you want a link to not get truncated, place a pair of characters in your text, and then paste the link between them... Like this: http://www.gpsworld.com/defense/eloran-and-ursanav-timing-everything-12744?utm_source=GPSutm_medium=emailutm_campaign=Defense-PNT_03_14_2012utm_content=eloran-and-ursanav-timing-everything-12744 -Chuck Harris Rob Kimberley wrote: Article on the recent Loran testing. http://www.gpsworld.com/defense/eloran-and-ursanav-timing-everything-12744?u tm_source=GPSutm_medium=emailutm_campaign=Defense-PNT_03_14_2012utm_conte nt=eloran-and-ursanav-timing-everything-12744 Hope that link doesn't get truncated. Rob Kimberley ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/14/12 9:14 PM, J. Forster wrote: On 3/14/12 8:07 PM, J. Forster wrote: John Like your thought. I seem to remember costas loops work like that to recover the carrier. Paul, It recovers a bipolar signal to steer the local VCO as well as the data.. It also needs a quadratue hybrid at the VCO frequency (although it might be fairly easy to make a quadrature oscillator vat 60 kHz.) One easy scheme is to make your VCO run at a multiple and divide down to generate the two quadrature square waves. Doesn't look like that works with the HP 117A. I don't know about other receivers. Had seen it in amsat many years ago. So perhaps an approach is to limit if possible the incoming signal. I'm not sure if it works properly with clipped (digital) dignals, off hand. Yes it will. Not w/o a quadrature drive to the mixer/multiplier. A square wave, multiplied by itself, has the same output as input. Oh... I was assuming you had the two quadrature square waves (which are just like the saturated LO for the mixer in RF land) Though further simple dumb thought. A NE602 or SA602 or also teh 612 series. All the same mixer circuit (Or multiplier)will double the incoming frequency if you delay the incoming by 90 degrees I think. Sine and Cosine are orthogonal. You need to do (Sine)*(Sine) sin^2 (wt) = 1/2(1 - cos (2wt) This is like the classic squaring technique to receive PN coded signals without knowing the code. (it's used in some codeless GPS receivers.. you can retrieve frequency and phase) A Costas Loop recovers the bit stream and the carrier frequency (from the local VCO) from a BPSK. It is self syncronizing. Yes.. but if you don't care about the bitstream, and you want simpler hardware, squaring works. (especially if the modulator doesn't have good carrier suppression) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Poul-Henning Kamp p...@phk.freebsd.dk Sender: time-nuts-boun...@febo.com Date: Wed, 14 Mar 2012 22:16:38 To: Discussion of precise time and frequency measurementtime-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] WWVB BPSK Receiver Project? In message 4f6116ce.7080...@pacific.net, Brooke Clarke writes: I sure would like a WWVB BPSK receiver for the new modulation. I've been playing with SDR and VLF signals for ages. What you want is an antenna, a 1MSPS ADC and a fast-ish CPU. One very interesting thing you can do with that, is to make a buffer 1000 samples long, and continously average the received signal into it, round-robin format. That amounts to a comb-filter for every n*1kHz signal, and a trivial sin/cos multiplicator will give you the phase and amplitude of every single radiotransmitter on n*1kHz up to your antialias filter at the same time. If you have CPU power, you can also receive Loran-C by making the buffer GRI*10 (or *20, if you want the code) samples long. I've long thought about building a board with one of the faster ARM CPUs and a 1MSPS 16bit ADC for this, but nobody else seemed interested, so I've just used my hacked up rig. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] eLORAN and UrsaNav - GPS World
Possibly complementing the GPS World article, Chris Stout of UrsaNav is presenting a paper on LF Time Transfer at a NIST conference next week. http://tf.nist.gov/seminars/WSTS/WSTSAgenda.html -- Björn ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, 15 Mar 2012 13:50:08 + shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I think Poul-Henning is refering to his AducLoran receiver, which used a 1Msps ADC [1]. I dont remember what he exactly does with the signal, but IIRC he uses a 40MHz uC which leaves him with 40 Cycles per sample, which is quite a lot if you only do just some math calculation to detect the start of a second... And unlike with the FPGA, it does not take more time to process 8bit or 24 bit samples as the uC works with 32bit numbers anyways. Attila Kinali [1] http://phk.freebsd.dk/AducLoran/ -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 6:50 AM, shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. You could use an FPGA, but the data rate isn't all that high. The signal is fairly narrow band (1 kHz, I should think). What you might want to do is build a ADC/FPGA combo that provides a nice USB/Ethernet interface for the sample stream which has been digital downconverted and filtered. the FPGA takes care of the icky glue logic details and does a bit of decimation. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Dear american colleagues, as I read last few posts about WWVB, I am very tempted to return to LF time signal fun. As I wrote you, there vere very good results using cheap 2 IC circuitry and a PC with our local DCF77 signal. Under influence of this maillist, I am thinking about recreating of the receiver using recent MCU, ferrite rod on one side, optional 10MHz input, USB device acting as a standard USB audio class soundcard output. Everything working with GNUradio, MATLAB, HAM waterfalls etc. out of the box. Could be used as an audio frequency front-end for HAM radio, too. Would you be interested in such a kit? It should be $100 all inclusive, if there will be more people involved (let say 5-10) to cover PCBs. Best regards, Marek ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] eLORAN and UrsaNav - GPS World
Thanks for that Chuck...I knew there should be a way of doing it. :-) Rob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris Sent: 15 March 2012 13:14 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] eLORAN and UrsaNav - GPS World If you want a link to not get truncated, place a pair of characters in your text, and then paste the link between them... Like this: http://www.gpsworld.com/defense/eloran-and-ursanav-timing-everything-12744? utm_source=GPSutm_medium=emailutm_campaign=Defense-PNT_03_14_2012utm_cont ent=eloran-and-ursanav-timing-everything-12744 -Chuck Harris Rob Kimberley wrote: Article on the recent Loran testing. http://www.gpsworld.com/defense/eloran-and-ursanav-timing-everything-1 2744?u tm_source=GPSutm_medium=emailutm_campaign=Defense-PNT_03_14_2012utm _conte nt=eloran-and-ursanav-timing-everything-12744 Hope that link doesn't get truncated. Rob Kimberley ___ time-nuts mailing 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?
There are a number of sound cards (and have been for 10 years now) that can capture up to 95 KHz with extraordinary fidelity. They sample at 192 KHz and usually have 24 bit converters good tor 20+ bits. These can capture the complete FM MPX output pretty easily. Some of the newer ADC's have less that .001% THD at 192 KHz sampling. The AK5394a for example has -105 dB THD at 1 KHz. Can be had as a chip for about $22 ea if you want to build your own. Some current motherboards have an SPDIF input that can handle the 192 KHz sample rate. The next challenge is getting the OS to handle it, not difficult. Demian ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. -John On Wed, 14 Mar 2012 18:14:56 -0700 WB6BNQ wb6...@cox.net wrote: His enthusiasm was aimed totally at new products. Although he admitted it leaves all the real Timenut type people, actually using the system for its intended purpose, out in the cold, he really did not seem to care. Pointing out that a failure with the GPS system left WWVB as the only alternate did not seem to matter either. Could someone be so kind and could explain me what the problem with the BPSK modulation is? I mean the phase of WWVB shifts around several 10us during sunrise/sunset already... Not to talk about the changing propagation conditions. Just see [1] for an example of what's happening. Yes, for those devices that lock on the phase, you'd have to change their correction/detection loop, but overall, they should still work. Attila Kinali [1] http://www.febo.com/time-freq/wwvb/spectracom/index.html -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Jim wrote: a square wave, multiplied by itself, has the same output as input. Oh... I was assuming you had the two quadrature square waves (which are just like the saturated LO for the mixer in RF land) You don't have two square waves in quadrature. You have the (amplified) signal from the antenna. A Costas Loop recovers the bit stream and the carrier frequency (from the local VCO) from a BPSK. It is self syncronizing. Yes.. but if you don't care about the bitstream, and you want simpler hardware, squaring works. (especially if the modulator doesn't have good carrier suppression) I think a better implementation would be: Analog multiplier Adaptive comparator (slice level = 1/2 P_P signal) Flip Flop Rabbit ears filter at 60 kHz -John = ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 7:49 AM, J. Forster wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. and the cleverness of the Costas loop is that it uses (an estimate of) the current data bit (the output of the I arm) to flip the sign of the error signal from the quadrature arm. There's a lot of scope for modification of the basic linear Costas loop. Hard/soft limiters in either or both arms, you've got three filters (the two arm filters and the loop filter) to fool with, plus all sorts of schemes using data aiding where you get feedback from your symbol slicer to help do a better job on the carrier tracking. You can also run your loop with hard limited signal input (makes the mixers turn into XOR gates). If you don't need the bits in real time (i.e. you can tolerate some latency), then you can also build tracking loops that effectively look into the future; i.e. make decisions on carrier and bit at time t using future data from tnow, as well as t=[-infinity, now]. Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Why make it simple when complicated also works? -John On 3/15/12 7:49 AM, J. Forster wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. and the cleverness of the Costas loop is that it uses (an estimate of) the current data bit (the output of the I arm) to flip the sign of the error signal from the quadrature arm. There's a lot of scope for modification of the basic linear Costas loop. Hard/soft limiters in either or both arms, you've got three filters (the two arm filters and the loop filter) to fool with, plus all sorts of schemes using data aiding where you get feedback from your symbol slicer to help do a better job on the carrier tracking. You can also run your loop with hard limited signal input (makes the mixers turn into XOR gates). If you don't need the bits in real time (i.e. you can tolerate some latency), then you can also build tracking loops that effectively look into the future; i.e. make decisions on carrier and bit at time t using future data from tnow, as well as t=[-infinity, now]. Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, 15 Mar 2012 07:49:15 -0700 (PDT) J. Forster j...@quikus.com wrote: Suppose the modulation is not present. The output of the phase detector that steers the local standard ot indicator works correctly. Now reverse the 60 kHz carrier. The phase detector works exactly thye opposite way... wrong. Now alternate between 0 and 190 degrees. The loop alternate works between exactly right and exactly wrong... it dithers around and the output is a measure of the ratio of 1's to 0's and is utterly useless. That under the assumption, that they do not make sure that the average phase is zeros out (or converges to 90°). I have not found anything taht suggests this... on the other hand, there is nothing that suggests the contrary either. But you didnt address my main point yet: The phase of the WWVB signal is already fluctuating a lot, just by natural occuring atmospherical noise. If a 180° phase shift does destabilize your PLL, what does these shifts which are much larger do? Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FE5680A Calibration
Hi Drive the GPS pps into the set input on a flip flop, drive the pps from the FE into the reset input. Use the UC10 to measure the period of the waveform on the Q output. Not super high resolution, but if you are patient, you can get the job done. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Sent: Wednesday, March 14, 2012 7:34 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FE5680A Calibration I picked up a gimpy Beckman UC10 universal counter not long ago for about $10 from Ebay. Even better, I just repaired a Tektronix 7D15 (it has a whole board full of those junk TI integrated circuit sockets which need to be replaced) although you need to leave an entire oscilloscope mainframe on to use it. The advantage of the later is adjustable slope, sensitivity, and triggering. On Wed, 14 Mar 2012 17:50:28 -0400, Bob Camp li...@rtty.us wrote: At least the don't mess to much with it part has sunk in. That puts you ahead of most people at this point. A usable counter should be a sub $100 sort of thing either at auction or surplus. With some careful shopping it can be a sub $40 item. On Mar 14, 2012, at 4:25 PM, Chris Stake st...@btinternet.com wrote: Hi Bob, Thanks for pointing-out the noisy output of the FE5680A. I'll probably try to lock a crystal oscillator to it. Unfortunately I don't have a suitable counter. I was hoping I could use some sort of higher frequency standard but I confess I had not really grasped the fact that the unit may well be within millihertz of the nominal frequency: too delicate to twiddle with anything other than precision equipment and long timebases. Kind regards Chris -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: 14 March 2012 16:57 To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] FE5680A Calibration Hi Do you have a dual channel counter that you can put the GPS into on the start and the FE into as the stop? The HP 5334, 5335, and 5345 are all examples of this sort of counter. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Stake Sent: Wednesday, March 14, 2012 12:49 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] FE5680A Calibration Nice idea, But I haven't got a DSO and the persistence of my scope isn't good enough to view 10Mhz sampled at 1pps. Chris -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of EB4APL Sent: 14 March 2012 15:46 To: time-nuts@febo.com Subject: Re: [time-nuts] FE5680A Calibration My fast approach would be to trigger a scope with the 1 PPS from the GPS receiver and observe the how the 10 MHz output of your Rb drifts. 1 full cycle per second is 1 e-7 so you'll need to use an stopwatch to time long periods when you are fine adjusting . Building (or buying) a GPSDO allows yo to make the comparison between both 10 MHz outputs without the jitter in the GPS receiver 1 PPS. Probably others in this list can suggest more elaborated and convenient approaches to this. On 14/03/2012 16:17, Chris Stake wrote: Hello all, I purchased a FE5680A from a Chinese Ebay vendor. I have connected it to a 16.5V laptop supply, added 7805-based 5V rail and a PMOS Fet switch to drive a LED for the locked signal. I can communicate with it using the excellent Fe5680Calibrator software. As received the frequency offset is set to Zero and the unit seems to work well. I plan to put it into service as a workshop frequency reference and so would like to set it close to 10.0Mhz. I have various oscillator modules, signal generators, SDR receivers, GPS receivers, a scanner, some uncalibrated test-gear. I live in a river valley in North Devon UK so radio reception is a bit restricted but I receive digital television via a masthead amplifier and long downlead. Could someone please suggest a way of going about this? Regards Chris Stake ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi- bin/mailman/listinfo/time- nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
Re: [time-nuts] WWVB BPSK Receiver Project?
Hi If you can handle the data rates for Loran at 100 KHz with a micro, then you should be able to handle the data rates for something at 60 KHz. My guess is that a simple I know what the waveform is now compare it approach would not be terribly processor intensive. Put another way, you can easily predict exactly what the signal will be doing at any instant. You just need to steer to the error from that prediction. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali Sent: Thursday, March 15, 2012 10:26 AM To: shali...@gmail.com; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] WWVB BPSK Receiver Project? On Thu, 15 Mar 2012 13:50:08 + shali...@gmail.com wrote: Poul-Henning, Do you need 16 bits or can you get by with a 12 bit ADC? Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I think Poul-Henning is refering to his AducLoran receiver, which used a 1Msps ADC [1]. I dont remember what he exactly does with the signal, but IIRC he uses a 40MHz uC which leaves him with 40 Cycles per sample, which is quite a lot if you only do just some math calculation to detect the start of a second... And unlike with the FPGA, it does not take more time to process 8bit or 24 bit samples as the uC works with 32bit numbers anyways. Attila Kinali [1] http://phk.freebsd.dk/AducLoran/ -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] broadband MPX signal stereo
I heard a broadband sound-card like EMU0202 should work. I asked because of the various people on the list with expensive test equipment one should be able to record a good sample. Looks there is no interest. - Henry Azelio Boriani schrieb: Are you sure that a .WAV file can support the full MPX stereo and RDS signal? I suspect that you need raw samples that a sound card can't handle. The output of a FM stereo and RDS radio discriminator are beyond the usual audio bandwidth. The output of the discriminator full bandwidth is first used by the RDS decoder and then (partially filtered) by the stereo deMPX and then by the audio processor. On Thu, Mar 15, 2012 at 2:08 AM, ehydra ehy...@arcor.de wrote: Hi! I'm looking for a sampled wave-file from a radio receiver MPX-signal including the RDS frequency band around 57KHz. I searched the Net but found just nothing that worked. So I ask here. Maybe someone has the possibility to sample a couple of seconds. -- 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)
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.
[time-nuts] Tracor 308-B Rubidium Standard Question
Hi, I'm investigating a Tracor 308-B standard. I can see the modulation frequency, but there's no trace of the second harmonic so the unit won't lock. I opened up the physics package and the lamp does light, but it's very weak. Has anyone tried to rejuvenate one of these bulbs by heating it? Any tricks to watch out for? I already know that I hate that little wire that's used for starting the bulb. Is using heat to rejuvenate a Rubidium lamp a generic trick that's worth trying with any Rubidium, or just particular ones? Thanks, Ed ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, Mar 15, 2012 at 1:48 AM, Chuck Forsberg WA7KGX N2469R c...@omen.com wrote: How about this: Generate a precise 60 KHz signal from a GPSDO's 10 MHz. Modulate it with 1 bit audio generated by a Linux program which would know about DST. The standard NTP source code distribution comes with a program to generate the time code. So you'd not have the write it yourself. It's purpose is to test the the WWV drivers n NTP. It is not built by default, from memory the source is in a directory called test. But for those radio clocks in your house the new WWVB signal should just work. They will not notice the phase modulation Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] broadband MPX signal stereo
On Thu, Mar 15, 2012 at 3:56 AM, Azelio Boriani azelio.bori...@screen.it wrote: Are you sure that a .WAV file can support the full MPX stereo and RDS signal? I suspect that you need raw samples that a sound card can't handle. Some audio interfaces have a low pass filter to cut off at about 20KHz but many don't have the filter. The user manual should list the bandwidth of the interface. Mine claims to be flat out to 40KHz. But it varies. For example the EMU 2020 user manual reads Frequency Response (min gain, 20Hz-20kHz): +0.0/-0.07dB But what happens after 20KHz? The specs don't say. You have to test it yourself and see. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
The major advantage of simply sampling at 192K is that it is so simple. Not much hardware outside of a good audio interface is required. But the mixer is attractive because then you can make it a quadrature mixer and then sample with both stereo channels. One then could use a more common 44.1 or 48K sample rate. You trade a bit of hardware up front for reduced processing requirements later. On Thu, Mar 15, 2012 at 12:38 AM, Peter Monta pmo...@gmail.com wrote: Many A/D converter systems use a sample and hold before the A/D converter. If you do the same before your sound card (your A/D converter) and drive the SH with an audio output from your sound card, say at 6.1 kHz you would get a 1 kHz signal into your sound card to process. You can call it under sampling aliasing or whatever. Yes, this would work, but instantaneous sampling would tend to alias in many harmonics, requiring good prefiltering at RF (if you can call 60 kHz RF). Just as easy would be a mixer from CMOS switches, driven say at 50 kHz to get 10 kHz into the sound card. The WWVB signal apparently has a double-sided bandwidth of about 1200 Hz (not clear from the paper if that means 3 dB bandwidth or something else). To get all of the signal something like 2 or 3 kHz might be safest, requiring an IF of several kHz at least. Cheers, Peter ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] broadband MPX signal stereo
Hi I think you will find that the 2020 is a bit noisy above 20 KHz... Also there are a lot of chips that drop in a ~40 KHz low pass filter when sampling at 196 KHz. It's a brick wall, so you get near nothing above the cutoff frequency. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ehydra Sent: Thursday, March 15, 2012 2:44 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] broadband MPX signal stereo I heard a broadband sound-card like EMU0202 should work. I asked because of the various people on the list with expensive test equipment one should be able to record a good sample. Looks there is no interest. - Henry Azelio Boriani schrieb: Are you sure that a .WAV file can support the full MPX stereo and RDS signal? I suspect that you need raw samples that a sound card can't handle. The output of a FM stereo and RDS radio discriminator are beyond the usual audio bandwidth. The output of the discriminator full bandwidth is first used by the RDS decoder and then (partially filtered) by the stereo deMPX and then by the audio processor. On Thu, Mar 15, 2012 at 2:08 AM, ehydra ehy...@arcor.de wrote: Hi! I'm looking for a sampled wave-file from a radio receiver MPX-signal including the RDS frequency band around 57KHz. I searched the Net but found just nothing that worked. So I ask here. Maybe someone has the possibility to sample a couple of seconds. -- 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] broadband MPX signal stereo
Yes, there is people who have what in the past was expensive test equipment and now can be bought by 1/10 of the original price. The problem is that you need someone who can record 2 seconds of a signal that is slightly beyond the actual sound card sampling capability. A signal that you can have by simply tuning your radio and hooking directly to the FM discriminator output. This signal is available virtually all over the world. AFAIK there was in the past no expensive test equipment that can sample and record a file. Now there are: the RS SMBV100 can sample and play any signal upto 3GHz with the full options fitted and the companion recorder/player for 200K euros, the file produced are not PC compatible, of course. On Thu, Mar 15, 2012 at 8:31 PM, Chris Albertson albertson.ch...@gmail.comwrote: On Thu, Mar 15, 2012 at 3:56 AM, Azelio Boriani azelio.bori...@screen.it wrote: Are you sure that a .WAV file can support the full MPX stereo and RDS signal? I suspect that you need raw samples that a sound card can't handle. Some audio interfaces have a low pass filter to cut off at about 20KHz but many don't have the filter. The user manual should list the bandwidth of the interface. Mine claims to be flat out to 40KHz. But it varies. For example the EMU 2020 user manual reads Frequency Response (min gain, 20Hz-20kHz): +0.0/-0.07dB But what happens after 20KHz? The specs don't say. You have to test it yourself and see. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, 15 Mar 2012 20:02:31 +0100 (CET) Marek Peca ma...@duch.cz wrote: Of course I mean it should pick your 60kHz, as well as other systems known to me: Japanese 40kHz, 60kHz, Swiss 75kHz, British 60kHz and possibly others. Highly unsure about Russian 25kHz, even do not know, whether it is still on air. HBG has been switched of earlier this year. So DCF77 and Alison are the only time LF senders left in continental europe. 1. first, deliver simple USB audio sampling unit with 77.5kHz-proven ferrite rod preamplifier, ready to work with 40..80kHz signals at least; every processing within PC / Gnuradio framework; After the discussion here, i had a similar idea. I want to use the STM32F4xx for something bigger and bought two discovery boards to get used to them. But i didn't know what i want to do... it should be something usefull.. at least half way usefull. And the discussion here prodded me that i could do a SDR DCF77 with that. A 160MHz 32bit uC with hardware single precision floatingpoint is way more than fast enough to handle that :-) If i've time, i sketch the HW this weekend and build it as soon as i've time... And then it's just software :-) Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, 15 Mar 2012 22:51:55 +0100 Attila Kinali att...@kinali.ch wrote: Of course I mean it should pick your 60kHz, as well as other systems known to me: Japanese 40kHz, 60kHz, Swiss 75kHz, British 60kHz and possibly others. Highly unsure about Russian 25kHz, even do not know, whether it is still on air. HBG has been switched of earlier this year. So DCF77 and Alison are the only time LF senders left in continental europe. Err,, it's Allouis. Don't ask me where that Alison came from... Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long ago? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. I have considered FPGA, DSP would probably be more suitable, but if I can do it in an ARM with C/Assy code, I prefer that. I think Poul-Henning is refering to his AducLoran receiver, That's one of the few experiements I bothered to document, I've been doing similar stuff with DCF77 phase-code etc. As long as you're after time/freq, you can use very deep averaging which only takes a few instructions per sample, so for instance the 42MHz Aduc7026 chip copes nicely with a single Loran-C signal. I think I could squeeze a Loran-C navigation solution into it, if I wanted to and as long as we're not talking too high speeds (again allowing deep averaging) but I have not bothered. A modern PC has a lot of computing power for stuff like this, and is great for prototyping code, before dumping into a smaller chip. That's how I found out that the circular-buffer averaging comb-filter is a much better and stronger signal discriminator than almost anything else you can come up with, for frequency/phase reception. See for instance: http://phk.freebsd.dk/loran-c/CW/ -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, Mar 15, 2012 at 2:51 PM, Attila Kinali att...@kinali.ch wrote: After the discussion here, i had a similar idea. I want to use the STM32F4xx for something bigger and bought two discovery boards to get used to them. But i didn't know what i want to do... it should be something usefull.. at least half way usefull. And the discussion here prodded me that i could do a SDR DCF77 with that. A 160MHz 32bit uC with hardware single precision floatingpoint is way more than fast enough to handle that :- You might want to choose a platform that can run either dttsp or Gnuradio/GRC or else you will be writing from scratch. You will spend weeks doing what could be done in hours. Look at these http://dttsp.sourceforge.net/ http://www.oz9aec.net/index.php/gnu-radio/grc-examples Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
In message Pine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
On Thu, 15 Mar 2012 22:27:53 +
Poul-Henning Kamp p...@phk.freebsd.dk wrote:
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
How good would that DAC need to be?
1-4MB RAM
over a 256kB RAM it's get pretty thin if you want to stay in the uC
busines. Unless you want to use an ARM9 or better with external SDRAM
and Flash. But those are mostly BGA (very few QFP chips out there) and
they are assumed to run Linux or Windows CE on them... Support for bare
metal stuff is pretty thin.
On the other hand, if you dont have to support an OS and work on the
bare metal, you can get away with very little RAM. 128k is a damn lot
if you have to fill it with usefull data structures ;-)
USB2 interface
Which would mean you need a pretty recent chip as HighSpeed USB has not
been introduced into the uC world for more than 2 years or so.
Attila Kinali
--
Why does it take years to find the answers to
the questions one should have asked long ago?
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Re: [time-nuts] WWVB BPSK Receiver Project?
On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom.Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second.An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
PHK, I'm interested in your circular averaging buffer: suppose 1K long, the 1st sample goes into position 0, the 2nd into 1 ... the 1000th into 999 or, the 1st gets scaled and then summed with that already present in position 0 then the result back in position 0? And so on, of course, for position 1, 2 ... On Thu, Mar 15, 2012 at 11:48 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom.Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second.An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
That would be big expensive filter. All you really need is the average of the last N samples. But with WWVB the bits are amplitude modulated at one bit per second. so you want a big time constant on any AGC, maybe 100 seconds. If you are sampling at 192K that would use way to much memory if you stored each sample. Better to only keep running statistics.For AGC you don't need to process every sample, you can feed the AGC a subset of the sample stream. But with a 24b-t ADC you may not need AGC On Thu, Mar 15, 2012 at 4:01 PM, Azelio Boriani azelio.bori...@screen.it wrote: PHK, I'm interested in your circular averaging buffer: suppose 1K long, the 1st sample goes into position 0, the 2nd into 1 ... the 1000th into 999 or, the 1st gets scaled and then summed with that already present in position 0 then the result back in position 0? And so on, of course, for position 1, 2 ... On Thu, Mar 15, 2012 at 11:48 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp p...@phk.freebsd.dk wrote: In message 20120315152620.8347488e049854218aed4...@kinali.ch, Attila Kinali w rites: Do you need 16 bits or can you get by with a 12 bit ADC? In general: The more the merrier, for a digital dude like me, having more bits is easier than getting AGC working correctly :-) Have you considered using an FPGA for signal processing? It seems you need a fairly serious CPU to handle that much data. That much data we are talking about 192K samples per second. I can routinely record multiple tracks of 192K audio and do processing in real time and the CPU meter hardly moves the bottom. Even a gigabit per second Ethernet port is not a lot of data on a modern computer. FPGAs and DSP come into play if you are talking about tens of millions of samples per second with data rates above say 200Mb/Sec But the rate from an audio interface running 192K and 24-bits is still under one megabyte per second. An interesting ratio is the number of CPU cycles available to process one sample. On my Apple iMac that would be about roughly 200,000 operations per data sample. In real life SDR receivers even an older CPU can process the I and Q channels and maintain a large graphic screen and send and receive data over a network and still not be maxed out Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] NIST's WWVB phase modulation format paper from PTTI 2011
If I'm right, that's another broken egg in the frequency reference basket. I read the paper, but I could use an expert ruling from the list: What does this actually mean for my Spectracom 8170 and Spectracom 8164, i.e. the twins? The latter I frankly don't use much (I'm early in the time-nuts disease progression), but the 8170 I want to continue to rely on, at least to set itself. A little phase noise I can tolerate. But the recent transmission-format experiments coincided (to a first approximation) with the recent coronal mass ejection that knocked the 8170 on its ass for most of a week, so my observations are not conclusive. The circuit (still a-building) to set my SWCC clock will take the 1PPS edge, but the speed of the solenoid, not to mention the time constant of the current-loop, I'm sure vastly outweighs this new source of error. Right? Will the strip-chart recorder on the 8164 provide a new source of amusement, as it tries to plot the 180-degree phase changes every second? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 8:10 AM, J. Forster wrote: Why make it simple when complicated also works? -John Can't get your doctorate doing something someone else has already done...grin Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] WWVB Modulation Tests
Is there anyone that had a Tracor 599J or K on line when the new modulation test was going on? Does anyone know when the next test is to be performed? Sam ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 3:24 PM, Chris Albertson wrote: On Thu, Mar 15, 2012 at 2:51 PM, Attila Kinaliatt...@kinali.ch wrote: After the discussion here, i had a similar idea. I want to use the STM32F4xx for something bigger and bought two discovery boards to get used to them. But i didn't know what i want to do... it should be something usefull.. at least half way usefull. And the discussion here prodded me that i could do a SDR DCF77 with that. A 160MHz 32bit uC with hardware single precision floatingpoint is way more than fast enough to handle that :- You might want to choose a platform that can run either dttsp or Gnuradio/GRC or else you will be writing from scratch. You will spend weeks doing what could be done in hours. Look at these http://dttsp.sourceforge.net/ documentation for dttsp is less than wonderful http://www.oz9aec.net/index.php/gnu-radio/grc-examples seems to be a bit more diverse usage for gnuradio, so more examples and documentation Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
On 3/15/12 3:27 PM, Poul-Henning Kamp wrote:
In messagePine.LNX.4.64.1203152001370.3542@tesla, Marek Peca writes:
Yes, it should work on any USB audio capable OS, ie. Linux, Windows, MacOS etc.
I would like to recommend against this approach for a number of reasons.
First, yes, while you can do undersampling and such, it puts very high
requirements on your analog filters.
The reason I use 1MSPS is that it allows me to use a very sloppy low-pass
filter filter which just cuts off somewhere around 150-200 kHz, and do
everything else in software.
and if you have any sort of processing behind the 1MSPS, you can do a
simple digital filter and decimate.
This means that I have no phase/group-delay distortion in the analog
part that I need to compensate in software.
It also means that I don't have to change hardware to play with different
signals, they're all there, all the time, for instance the stuff under
http://phk.freebsd.dk/Leap/
is pulled out that way.
If I, based on my design, were to design a gadget for doing VLF
time-nuts stuff, it would be:
Floating Input trafo with center-tap for powering antenna
16 bit 1MSPS ADC
ARM chip
10MHz clock input
1PPS sync input
1PPS sync output
(DAC output for {Rb|Ocxo}DO use ?)
1-4MB RAM
USB2 interface
Sending 2MB/s through a serial port profile is not a big problem
for USB2 or for that matter for an operating system, so you can
easily grap full spectrum and play with your your PC, and once you
have made some of it work, you can compile the same code and and
download it to the ARM chip, and use the serial port only for
stats/summary/(Tek4010-graphs) or you can use another USB profile
or whatever.
The ARM chip is plenty powerful to do pretty much anything you
are to on its own once you give it the code to do so.
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[time-nuts] Xtendwave
WWVB It seems that a commercial venture is driving this. Probably with all of the research at taxpayer expense. See: http://www.xtendwave.com/HD%20Time.pdf also www.extendwave.com ___ time-nuts mailing 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] Xtendwave
Xtendwave is a fabless semiconductor company with technologies that improve capacity and range in wired and wireless networks . . . translated: We thought up something that works sort of on paper and we want somebody to do all the grunting to make it really work and just maybe it really will . . . Oh, and just send money Don Sam Reaves WWVB It seems that a commercial venture is driving this. Probably with all of the research at taxpayer expense. See: http://www.xtendwave.com/HD%20Time.pdf also www.extendwave.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Neither the voice of authority nor the weight of reason and argument are as significant as experiment, for thence comes quiet to the mind. R. Bacon If you don't know what it is, don't poke it. Ghost in the Shell Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
On 3/15/12 9:41 PM, Chris Albertson wrote: On Thu, Mar 15, 2012 at 8:45 PM, Jim Luxjim...@earthlink.net wrote: http://dttsp.sourceforge.net/ documentation for dttsp is less than wonderful http://www.oz9aec.net/index.**php/gnu-radio/grc-exampleshttp://www.oz9aec.net/index.php/gnu-radio/grc-examples seems to be a bit more diverse usage for gnuradio, so more examples and documentation dttsp has by far the larger in-use user based because it is the engine used by PowerSDR by Flex Radio. It is also used by the HPSDR group. See these links http://www.flex-radio.com/ http://openhpsdr.org/ But you are right in that using dttsp is something that might take a long tome to learn. The above user group tends to have many appliance users and a few programers so learning is not so much of an issue If there are more than half a dozen people actually using dttsp, in the sense of modifying it, or doing something other than creating a UI for it, I'd be pretty surprised. It's pretty much a product of the two main authors. As you say, the learning curve is exceedingly steep, especially if you want to understand the architecture and internal structure. You could probably go in and do spot changes without breaking too much, but any sort of radical change (like adding a new demodulator) would be a pretty big challenge. The fact that it's the core of PowerSDR means that over the years, it's had a lot of customization for that particular application. Someone trying to decode PSK WWVB isn't going to be interested in the latency of the CW keyer or the performance of the automated notch filter. GNU Radio is popular in Universities where as soon as something works they toss it out. It's quite a bit easier to program or if you like there is GRC that allows visual programming.I think this is better because it allows a wider number of people to contribute. it's much more componentized and the source of the components is broader. Probably not as finished as something like PowerSDR, but much easier to bite off small chunks. For simple tasks, there are also tools like DL4YHF(?) spectrumlab. http://www.qsl.net/d/dl4yhf/spectra1.html it has: # Decoder for some time-code transmitters: MSF(60kHz), HBG(75kHz), DCF77 (77.5kHz) can now be used to set your PC clock to a high accuracy. All you need is your longwave receiver and the soundcard. # Modulator and decoder for some 'experimental' digital communication modes like PSK31, BPSK, QPSK, FSK, multi-tone HELL, MSK (minimum shift keying since 2004-12), transmission and reception of letters with a small 'terminal' window. I've used it a lot for a variety of tasks (a Doppler radar, for one thing) My suggestion to use a platform where these two libraries run was really to say that you should not write this on bare hardware. It's a good way to paint yourself into a corner and have to start over to add some new feature we can't think of today. Another idea, if you have access (e.g. student licenses or thru work) is Matlab/Simulink and real-time-workshop. All the building blocks are there, you just hook them up. Pretty pricey if you're not in the educational bucket, though. And Octave doesn't really have all the cool toolboxes that Matlab does. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] WWVB BPSK Receiver Project?
Frankly, my dear, I'd rather be a generalist. -John On 3/15/12 8:10 AM, J. Forster wrote: Why make it simple when complicated also works? -John Can't get your doctorate doing something someone else has already done...grin Enormous literature out there on this, and it's been grist for many a Master's or PhD dissertation. All in a quest to get ever closer to the Shannon limit... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] broadband MPX signal stereo
I have tested a number of soundcards and while the EMU 2020 has issues (serious jitter and noise from the USB interface) I can recommend the ESI Juli@ as having flat response and good SNR up to 90 KHz. It's a PCI card, no USB. I have measured the performance of FM MPX adapters and tested FM Transmitter performance with one. You get 24 bit at 192 X 2 continuously as long as you want. With some simple pre-filtering and gain you should be able to get some 60 KHz signal at very low levels. With a deep FFT I get to -130 dBFS easily. With the demo board for the AKM AK5345a I am getting better than -160dBFS. That has SPDIF out. Depending on the filter selection, most chips have a flat option, there is no significant phase shift up to frequencies close to the cutoff. I have tried and dumped a number of other sound cards that were dead ends. The ESI Juli@ is usually around $120. Demian __ Chris Albertson writes: Some audio interfaces have a low pass filter to cut off at about 20KHz but many don't have the filter. The user manual should list the bandwidth of the interface. Mine claims to be flat out to 40KHz. But it varies. For example the EMU 2020 user manual reads Frequency Response (min gain, 20Hz-20kHz): +0.0/-0.07dB But what happens after 20KHz? The specs don't say. You have to test it yourself and see. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
