Re: [time-nuts] C-Max Receiver Experiment
Update - I attempted to look at the analog signal. I looked at the output of the crystal. With the scope's low-pass filter turned on I was able to see a very weak sine wave with a period of roughly 15us. It was too weak for any analysis. http://www.fuzzythinking.com/wordpress/wp-content/uploads/2011/11/60khz.png I also looked at the demodulator out. This is a much larger amplitude signal, though it has already been rectified. However, I was able to see good correlation between it (blue) and the TCON output (yellow) http://www.fuzzythinking.com/wordpress/wp-content/uploads/2011/11/dem_out.png Most importantly, I've been reading up on the subject and have adjusted my expectations. I didn't realize that frequency measurements (like those done by the HP117 and Fluke 207) don't actually use the timecode part of the signal. Page 11 of http://tf.nist.gov/general/pdf/1383.pdf tells me that WWVB is 3-4 orders of magnitude better than WWV for frequency measurements, but that the two services' time uncertainties overlap and WWVB is at best 1 order better. As a matter of fact, my measurements of the C-MAX line up with the top end of that estimate (and Tom's :-)). I'm still planning on capturing a long set of timings, but I need to do some hardware mods first. Thanks, -Justin On Mon, Oct 31, 2011 at 1:04 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Hi David, Thanks for pointing out the problem with the figures in my webpage. I have fixed it. I'm going to attempt to capture the analog signal by probing the QOut pin. The updated images make the effects clearer. It will be interesting to see the image capture. Good point about precision - it's all relative. This is an extension of a previous project of mine - a clock I built around an LPro. Setting it to the Thunderbolt is a bit of a pain and I was hoping to build in the C-Max to make it more fire and forget. I was hoping for a time signal within several microseconds of UTC without the need of an outdoor antenna. Like most of my projects, the journey is more interesting than the destination, so even if I don't accomplish that goal I'm still having fun. Embedding a consumer GPS is probably the more practical solution. Thanks, -Justin Microseconds, no. Milliseconds perhaps. But sometimes nothing at all depending on the time of day and season of the year etc. etc. Let's hear more about the project as it progresses. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] C-Max Receiver Experiment
There's a nice set of WWVB 'scope traces here: http://leapsecond.com/pages/sony-wwvb/ /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] C-Max Receiver Experiment
It would be interesting to know what the analogue signal looks like, as many pieces of electrical and electronic equipment can radiate significantly on those frequencies. 60 KHz, AM Modulated, low bandwidth. Google will find the details at NIST's web site. Likely sources of interference are displays and switching power supplies. I think most modern switching supplies are now higher frequency. Beware of fluorescent lights. 5 or 10 years ago, the ones in the lab where I worked were roughly 50 KHz. -- 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] C-Max Receiver Experiment
In the late 70s I took a 6800 based micro I designed for Sidereal and developed CTU - Chuck's Terminal Unit, a program that ran an autostart responder on 80 meters. The computer ran 1000 non maskable interrupts per second. This powered Baudot send, receive, and distortion measurements. It also powered a software phase locked loop that synced to and decoded the WWVB signal. A loopstick with lots of turns and a trimmer fed into a FET gate makes for a very selective antenna. I also happened to have a 60 KHz crystal filter on hand. There weren't many switching power supplies back then and reception was passable. Today I have a Radio Shack clock that has great difficulty synching and two Oregon Scientific weather consoles that can't sync at all. -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] C-Max Receiver Experiment
From: Hal Murray [] It would be interesting to know what the analogue signal looks like, as many pieces of electrical and electronic equipment can radiate significantly on those frequencies. 60 KHz, AM Modulated, low bandwidth. Google will find the details at NIST's web site. Likely sources of interference are displays and switching power supplies. I think most modern switching supplies are now higher frequency. Beware of fluorescent lights. 5 or 10 years ago, the ones in the lab where I worked were roughly 50 KHz. Thanks, Hal. I know what the signal /should/ look like - I was thinking more of how it /actually/ appeared with Justin's setup, i.e. how much interference there actually was. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing 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] C-Max Receiver Experiment
On Mon, Oct 31, 2011 at 1:54 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?**page_id=29http://www.fuzzythinking.com/?page_id=29. It was a fun experiment and a great excuse to play with test equipment :-) Thanks, -JP Thanks for posting that, Justin, it was most interesting, and the reference to Brooke Clarke's page, which I did not know. It would be interesting to know what the analogue signal looks like, as many pieces of electrical and electronic equipment can radiate significantly on those frequencies. I expect you optimised the signal, though, as you've mentioned it. Are you sure the images are all correct? To me, your Fig 2 and Fig 3 images look identical, as do Fig 6 and Fig 7. Precision - well, that depends, doesn't it? Perhaps more precise than a very poor Internet connection? Better than no Internet connection at all! Certainly not GPS level. Cheers, David Hi David, Thanks for pointing out the problem with the figures in my webpage. I have fixed it. I'm going to attempt to capture the analog signal by probing the QOut pin. Good point about precision - it's all relative. This is an extension of a previous project of mine - a clock I built around an LPro. Setting it to the Thunderbolt is a bit of a pain and I was hoping to build in the C-Max to make it more fire and forget. I was hoping for a time signal within several microseconds of UTC without the need of an outdoor antenna. Like most of my projects, the journey is more interesting than the destination, so even if I don't accomplish that goal I'm still having fun. Embedding a consumer GPS is probably the more practical solution. Thanks, -Justin ___ time-nuts mailing 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] C-Max Receiver Experiment
Hi David, Thanks for pointing out the problem with the figures in my webpage. I have fixed it. I'm going to attempt to capture the analog signal by probing the QOut pin. The updated images make the effects clearer. It will be interesting to see the image capture. Good point about precision - it's all relative. This is an extension of a previous project of mine - a clock I built around an LPro. Setting it to the Thunderbolt is a bit of a pain and I was hoping to build in the C-Max to make it more fire and forget. I was hoping for a time signal within several microseconds of UTC without the need of an outdoor antenna. Like most of my projects, the journey is more interesting than the destination, so even if I don't accomplish that goal I'm still having fun. Embedding a consumer GPS is probably the more practical solution. Thanks, -Justin Microseconds, no. Milliseconds perhaps. But sometimes nothing at all depending on the time of day and season of the year etc. etc. Let's hear more about the project as it progresses. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing 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] C-Max Receiver Experiment
Hi JP: Have you tried this at midnight local time? Have Fun, Brooke Clarke http://www.PRC68.com http://www.End2PartyGovernment.com/ Justin Pinnix wrote: Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?page_id=29 . It was a fun experiment and a great excuse to play with test equipment :-) Thanks, -JP ___ time-nuts mailing 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] C-Max Receiver Experiment
Justin, A while back, I did some crude experiments with the C-Max CME6005 IC which is, I believe, used in that evaluation module. If memory serves, there were some rather severe restrictions documented in either the datasheet or an application note regarding the loading on the TCO/TCON pins. As I recall, it recommended a very minimal load (much less than what an LED might draw) and to not use the TCO and TCON outputs simultaneously. They claimed violating these recommendations would interfere with the receiver's operation, although I find it hard to believe. I'm certainly not suggesting this explains your results, only that you might want to look into it. Regards, Brent On Oct 30, 2011, at 16:09, Justin Pinnix jus...@fuzzythinking.com wrote: Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?page_id=29 . It was a fun experiment and a great excuse to play with test equipment :-) Thanks, -JP ___ time-nuts mailing 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] C-Max Receiver Experiment
You can use WWVB for timing but it is not as easy as buying the kit. First you need a better antenna and then a good location for it that is away from noisy electronics.then you have to let it disincline a local clock for a while. It will not be as good as GPS and you may never get 24 hour reception, even with a larger loop antenna. On Sun, Oct 30, 2011 at 2:07 PM, Justin Pinnix jus...@fuzzythinking.com wrote: Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?page_id=29 . -- 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] C-Max Receiver Experiment
Hi Brent, I actually saw that warning partway through the experiment. I disconnected it and didn't get any measurable difference. So, I put it back - it makes it easier to see what's going on :-) Based on several suggestions here, I think the next thing I'll try is capturing actual event arrival times. That will allow me to plot a histogram and let the experiment run all night (and day) to take advantage of different local times. Plus it gives me an excuse to buy (or build) a universal counter. Thanks, -Justin (AJ4MJ) On Sun, Oct 30, 2011 at 7:00 PM, KD0GLS kd0...@mninter.net wrote: Justin, A while back, I did some crude experiments with the C-Max CME6005 IC which is, I believe, used in that evaluation module. If memory serves, there were some rather severe restrictions documented in either the datasheet or an application note regarding the loading on the TCO/TCON pins. As I recall, it recommended a very minimal load (much less than what an LED might draw) and to not use the TCO and TCON outputs simultaneously. They claimed violating these recommendations would interfere with the receiver's operation, although I find it hard to believe. I'm certainly not suggesting this explains your results, only that you might want to look into it. Regards, Brent On Oct 30, 2011, at 16:09, Justin Pinnix jus...@fuzzythinking.com wrote: Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?page_id=29 . It was a fun experiment and a great excuse to play with test equipment :-) Thanks, -JP ___ time-nuts mailing 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] C-Max Receiver Experiment
Based on several suggestions here, I think the next thing I'll try is capturing actual event arrival times. That will allow me to plot a histogram and let the experiment run all night (and day) to take advantage of different local times. Plus it gives me an excuse to buy (or build) a universal counter. I'm assuming you have a TBolt or similar to use as a reference. I think one of tvb's picPET's and a PC with a serial port is all you need. http://www.leapsecond.com/pic/picpet.htm You probably need two of them (and 2 serial ports) so you can compare the WWVB pulses with the PPS from the TBolt. You could do that with a switch, assuming the WWVB pulses are late enough to be easily separated from the TBolt PPS. If things are stable enough, you could just flip the switch by hand, say once or twice a day for a minute or two. If not, you could use a bit from the printer port to drive a mux. If you have the PPS kernel support in your OS, you could also do it without the picPETs. Again, it either takes a switch or a second serial port. -- I think the real question is what will the adev graph look like? Long term it will be good, but how long, and where will it cross over what you are trying to discipline? I'm guessing it will take several days, maybe longer. That might fit well with with a recycled rubidium. -- 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] C-Max Receiver Experiment
Nuts, I recently picked up a C-Max evaluation kit from SparkFun to see if this $10 board could be used as a precision timing source. The short answer is no. The long answer is available at: http://www.fuzzythinking.com/?page_id=29 . It was a fun experiment and a great excuse to play with test equipment :-) Thanks, -JP Thanks for posting that, Justin, it was most interesting, and the reference to Brooke Clarke's page, which I did not know. It would be interesting to know what the analogue signal looks like, as many pieces of electrical and electronic equipment can radiate significantly on those frequencies. I expect you optimised the signal, though, as you've mentioned it. Are you sure the images are all correct? To me, your Fig 2 and Fig 3 images look identical, as do Fig 6 and Fig 7. Precision - well, that depends, doesn't it? Perhaps more precise than a very poor Internet connection? Better than no Internet connection at all! Certainly not GPS level. Cheers, David -- SatSignal software - quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
