Re: [time-nuts] HP 117/10509a...
Hi On Jul 8, 2012, at 1:17 AM, David J Taylor wrote: As an observer from across the pond: - presumably, the vast majority of users would not be affected. Yes, the wall clock and wrist watch people (I use both) would not be impacted according to NIST. I have seen no reports of, and not observed any impact on my stuff. - is there a technical solution which would be compatible with both old and new methods? Some alternative modulation scheme? The whole format of the change has been under the guise of a government investment in a technology company. That's taken the whole debate about modulation formats out of the public eye. The goals of the new modulation scheme are a bit unclear, so it's difficult to evaluate alternatives. One would *assume* that the cost of silicon to demodulate the new format is a major part of the decision on the new approach. That said, yes there has to be another way to do this that does not nuke the old gear. - is there not a testing period, where results can be fed back as to the compatibility or otherwise of the new scheme? There have been tests. There is no official / formal feedback mechanism for the tests. It's not totally clear what any of the testing results are. One would *guess* that they are testing a silicon implementation of their receiver in the field. One would also *guess* that nothing important is impacted by the modulation. - has there been any official response to your comments that the new scheme stops existing equipment working properly? The response has been: Yes we know this breaks your stuff. They have put that in writing. There is a somewhat vague promise that a box that translates the new format to one the old gear can use could / would / might be developed. No idea at all what such a box would look like or cost. Also no idea how well it would perform. - can you involve your members of the legislature, or would the be either inappropriate or a waste of time? Based on past experience - waste of time, even in an election year. The subject is to hard to understand and not enough voters are impacted. 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. ___ time-nuts mailing 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] disciplining sound card
Here the modified VHDL with the 48KHz and 96KHz clock out: LIBRARY IEEE; USE IEEE.std_logic_1164.ALL; USE IEEE.std_logic_unsigned.ALL; ENTITY FRSync IS PORT (ClkIN, RefIN: IN std_logic; -- ClkIN is 24.576MHz/1536-16KHz, RefIN is 10MHz/625-16KHz PWMOut, F48KHz, F96KHz: OUT std_logic); END ENTITY FRSync; ARCHITECTURE Proc4 OF FRsync IS SIGNAL Cnt5A: std_logic_vector (2 downto 0); SIGNAL Cnt125 std_logic_vector (6 downto 0); SIGNAL Cnt768 std_logic_vector (9 downto 0); SIGNAL Cnt2, Cnt5B, Cnt125N, Fr625: std_logic; BEGIN -- Dividers section Div125: PROCESS -- Divide the 10MHz first by 125 then by 5 BEGIN WAIT UNTIL RefIN'EVENT AND RefIN='1'; IF Cnt125=100 THEN Cnt125= (OTHERS= '0'); ELSE Cnt125= Cnt125+1; END IF; END PROCESS Div125; Div5A: PROCESS BEGIN WAIT UNTIL Cnt125(6)'EVENT AND Cnt125(6)='1'; IF Cnt5A=100 THEN Cnt5A= (OTHERS= '0'); ELSE Cnt5A= Cnt5A+1; END IF; END PROCESS Div5A; Div5B: PROCESS BEGIN WAIT UNTIL Cnt125N'EVENT AND Cnt125N='1'; Cnt5B= Cnt5A(1); END PROCESS Div5B; Div512: PROCESS -- Divide the 24.576MHz first by 512 BEGIN WAIT UNTIL ClkIN'EVENT AND ClkIN='1'; Cnt512= Cnt512+1; END PROCESS Div512; Div3A: PROCESS -- Divide by 3 50% duty BEGIN WAIT UNTIL Cnt512(8)'EVENT AND Cnt512(8)='1'; IF Cnt3A=10 THEN Cnt3A= (OTHERS= '0'); ELSE Cnt3A= Cnt3A+1; END IF; END PROCESS Div3A; Div3B: PROCESS BEGIN WAIT UNTIL Cnt512N'EVENT AND Cnt512N='1'; Cnt3B= Cnt3A(0); END PROCESS Div3B; -- Combinational section Cnt125N= NOT Cnt125(6); Cnt512N= NOT Cnt512(8); Fc3= '1' WHEN Div3A (0)='1' OR Div3B='1' ELSE '0'; -- 50% divide-by-3 Fr625= '1' WHEN Div5A (1)='1' OR Div5B='1' ELSE '0'; -- 50% divide-by-5 PWMOut= Fr625 XOR Fc3; -- The XOR needs exactly a 50% duty cycle F48KHz= Cnt512(8); F96KHz= Cnt512(7); END ARCHITECTURE Proc4; On Sun, Jul 8, 2012 at 7:34 AM, Demian Martin demian...@yahoo.com wrote: We need a better idea what the goal is. If it's to sample and digitize data at a specific time you may need to roll your own but if it's to figure out the time of an event or to look at spectral info a mid price premium soundcard like the Juli@ should be more than adequate. Knowing when in a sample cycle the actual sample was taken may not have a lot of meaning since the incoming info is bandlimited. The standard sample rates, 44.1, 48, 88.2, 96, 176.4 and 192 KHz have roots in the video world and are not nice numbers per 10 MHz references. Audio cards use either a single 24.576 MHz crystal and PLL to generate the other frequencies or both a 24.576 MHz and a 22.5792 MHz crystal. The ones with separate crystals do have less jitter. Word clock can only be used with difficulty if the card was not designed for it. You cannot force word clock and have the rest of the I2C buss work right. You can lock to an external SPDIF or AES signal (they are virtually the same except for some info bits and the signal levels. AES is 4V P-P differential into 110 Ohms. SPDIF is 1V P-P into 75 Ohms (an AES variant is the same). The same receivers are used for both. If absolute timing is important you can easily use an external capture device (TI, ADI and AKM all have very good demo boards) that you can clock. Clocking at 10 MHz will work in some systems on the external spdif input but many will reject it since it's too far from an accepted frequency. The high end cards that might will resample everything messing with your carefully captured data. If you do get the data in the existing software will give you confusing results. There may be a simple way to add a SMPTE time code to the data as its captured. It's done in the video industry. If you don't want a delta sigma ADC you can substitute a different kind but there will be tradeouts. Usually bit depth vs sample rate vs. accuracy. A simple way to discipline a 22.5792 and a 24.576 VCXO to a 10 MHz reference would be very interesting. A good way to verify the performance and any issues with a capture system would be to make a count down from the 10 MHz to an audio frequency and capture it. Do a really deep fft and look for stuff that should not be there (anything but the countdown). Demian Martin ___ time-nuts mailing 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] HP 117/10509a...
To be very clear here. There is not a box coming from NIST. They do not want the responsibility to maintain what ever it would be. The reason to make the change to the format is for better frequency and time distribution by this channel. It seeks to improve overall system gain and attempts to negate interference from MSF at least in regions of the east. Whats very interesting is that the silicon would in some way recover a carrier to recover the data. If that carrier happened to be on a pin of the chip then you might take advantage of this new method and it could then be used perhaps to drive the old equipment. I certainly have no problem with such an approach. But suspect the rcvr will be multi- and have to saythats not in the ole budget. Further wwvb has not been a great way to distribute frequency for 20 years. We time-nuts all have done far better with GPS. Granted no way to check it against anything else. So I simply do not understand the why of all of this. Not throwing stones here. Its just thats one big electric bill every month and there has to be a bit more clever alternate national freq dist method that would be far more economical and deliver better coverage and interference rejection. Think about it, this new modulation method with say 5 transmitters at lower power. Central site to control stability though at that point lots of other approaches come into play. Oh thats LORAN C sorry. Just very curious as to why the two approaches, especially since we also know eloran is also being explored. All of this is getting wa off topic. Regards Paul On 7/8/2012 6:50 AM, Bob Camp wrote: Hi On Jul 8, 2012, at 1:17 AM, David J Taylor wrote: As an observer from across the pond: - presumably, the vast majority of users would not be affected. Yes, the wall clock and wrist watch people (I use both) would not be impacted according to NIST. I have seen no reports of, and not observed any impact on my stuff. - is there a technical solution which would be compatible with both old and new methods? Some alternative modulation scheme? The whole format of the change has been under the guise of a government investment in a technology company. That's taken the whole debate about modulation formats out of the public eye. The goals of the new modulation scheme are a bit unclear, so it's difficult to evaluate alternatives. One would *assume* that the cost of silicon to demodulate the new format is a major part of the decision on the new approach. That said, yes there has to be another way to do this that does not nuke the old gear. - is there not a testing period, where results can be fed back as to the compatibility or otherwise of the new scheme? There have been tests. There is no official / formal feedback mechanism for the tests. It's not totally clear what any of the testing results are. One would *guess* that they are testing a silicon implementation of their receiver in the field. One would also *guess* that nothing important is impacted by the modulation. - has there been any official response to your comments that the new scheme stops existing equipment working properly? The response has been: Yes we know this breaks your stuff. They have put that in writing. There is a somewhat vague promise that a box that translates the new format to one the old gear can use could / would / might be developed. No idea at all what such a box would look like or cost. Also no idea how well it would perform. - can you involve your members of the legislature, or would the be either inappropriate or a waste of time? Based on past experience - waste of time, even in an election year. The subject is to hard to understand and not enough voters are impacted. 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. ___ time-nuts mailing 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] disciplining sound card
Demian Martin schrieb: If you don't want a delta sigma ADC you can substitute a different kind but there will be tradeouts. Usually bit depth vs sample rate vs. accuracy. Any market overview available? A simple way to discipline a 22.5792 and a 24.576 VCXO to a 10 MHz reference would be very interesting. I suggest one of the Cirrus audio clock PLLs. - Henry -- ehydra.dyndns.info ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP 117/10509a...
Hi I'd bet at least a cold order of fries that what ever chip comes out of this is going to be a cheap one. At least that will be true after a couple years. The target market is wall clocks… Bob On Jul 8, 2012, at 10:29 AM, paul wrote: To be very clear here. There is not a box coming from NIST. They do not want the responsibility to maintain what ever it would be. The reason to make the change to the format is for better frequency and time distribution by this channel. It seeks to improve overall system gain and attempts to negate interference from MSF at least in regions of the east. Whats very interesting is that the silicon would in some way recover a carrier to recover the data. If that carrier happened to be on a pin of the chip then you might take advantage of this new method and it could then be used perhaps to drive the old equipment. I certainly have no problem with such an approach. But suspect the rcvr will be multi- and have to saythats not in the ole budget. Further wwvb has not been a great way to distribute frequency for 20 years. We time-nuts all have done far better with GPS. Granted no way to check it against anything else. So I simply do not understand the why of all of this. Not throwing stones here. Its just thats one big electric bill every month and there has to be a bit more clever alternate national freq dist method that would be far more economical and deliver better coverage and interference rejection. Think about it, this new modulation method with say 5 transmitters at lower power. Central site to control stability though at that point lots of other approaches come into play. Oh thats LORAN C sorry. Just very curious as to why the two approaches, especially since we also know eloran is also being explored. All of this is getting wa off topic. Regards Paul On 7/8/2012 6:50 AM, Bob Camp wrote: Hi On Jul 8, 2012, at 1:17 AM, David J Taylor wrote: As an observer from across the pond: - presumably, the vast majority of users would not be affected. Yes, the wall clock and wrist watch people (I use both) would not be impacted according to NIST. I have seen no reports of, and not observed any impact on my stuff. - is there a technical solution which would be compatible with both old and new methods? Some alternative modulation scheme? The whole format of the change has been under the guise of a government investment in a technology company. That's taken the whole debate about modulation formats out of the public eye. The goals of the new modulation scheme are a bit unclear, so it's difficult to evaluate alternatives. One would *assume* that the cost of silicon to demodulate the new format is a major part of the decision on the new approach. That said, yes there has to be another way to do this that does not nuke the old gear. - is there not a testing period, where results can be fed back as to the compatibility or otherwise of the new scheme? There have been tests. There is no official / formal feedback mechanism for the tests. It's not totally clear what any of the testing results are. One would *guess* that they are testing a silicon implementation of their receiver in the field. One would also *guess* that nothing important is impacted by the modulation. - has there been any official response to your comments that the new scheme stops existing equipment working properly? The response has been: Yes we know this breaks your stuff. They have put that in writing. There is a somewhat vague promise that a box that translates the new format to one the old gear can use could / would / might be developed. No idea at all what such a box would look like or cost. Also no idea how well it would perform. - can you involve your members of the legislature, or would the be either inappropriate or a waste of time? Based on past experience - waste of time, even in an election year. The subject is to hard to understand and not enough voters are impacted. 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. ___ time-nuts mailing 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] HP 117/10509a...
IMO, a better way to provide the service would be to just turn a couple of LORAN-C stations back on. But that would be a tacit admission of another stupid government screwup. This WWVB scheme can possibly be spun as an 'improvement'- hence politically less distasteful, even if more expensive for the users. YMMV. , -John To be very clear here. There is not a box coming from NIST. They do not want the responsibility to maintain what ever it would be. The reason to make the change to the format is for better frequency and time distribution by this channel. It seeks to improve overall system gain and attempts to negate interference from MSF at least in regions of the east. Whats very interesting is that the silicon would in some way recover a carrier to recover the data. If that carrier happened to be on a pin of the chip then you might take advantage of this new method and it could then be used perhaps to drive the old equipment. I certainly have no problem with such an approach. But suspect the rcvr will be multi- and have to saythats not in the ole budget. Further wwvb has not been a great way to distribute frequency for 20 years. We time-nuts all have done far better with GPS. Granted no way to check it against anything else. So I simply do not understand the why of all of this. Not throwing stones here. Its just thats one big electric bill every month and there has to be a bit more clever alternate national freq dist method that would be far more economical and deliver better coverage and interference rejection. Think about it, this new modulation method with say 5 transmitters at lower power. Central site to control stability though at that point lots of other approaches come into play. Oh thats LORAN C sorry. Just very curious as to why the two approaches, especially since we also know eloran is also being explored. All of this is getting wa off topic. Regards Paul On 7/8/2012 6:50 AM, Bob Camp wrote: Hi On Jul 8, 2012, at 1:17 AM, David J Taylor wrote: As an observer from across the pond: - presumably, the vast majority of users would not be affected. Yes, the wall clock and wrist watch people (I use both) would not be impacted according to NIST. I have seen no reports of, and not observed any impact on my stuff. - is there a technical solution which would be compatible with both old and new methods? Some alternative modulation scheme? The whole format of the change has been under the guise of a government investment in a technology company. That's taken the whole debate about modulation formats out of the public eye. The goals of the new modulation scheme are a bit unclear, so it's difficult to evaluate alternatives. One would *assume* that the cost of silicon to demodulate the new format is a major part of the decision on the new approach. That said, yes there has to be another way to do this that does not nuke the old gear. - is there not a testing period, where results can be fed back as to the compatibility or otherwise of the new scheme? There have been tests. There is no official / formal feedback mechanism for the tests. It's not totally clear what any of the testing results are. One would *guess* that they are testing a silicon implementation of their receiver in the field. One would also *guess* that nothing important is impacted by the modulation. - has there been any official response to your comments that the new scheme stops existing equipment working properly? The response has been: Yes we know this breaks your stuff. They have put that in writing. There is a somewhat vague promise that a box that translates the new format to one the old gear can use could / would / might be developed. No idea at all what such a box would look like or cost. Also no idea how well it would perform. - can you involve your members of the legislature, or would the be either inappropriate or a waste of time? Based on past experience - waste of time, even in an election year. The subject is to hard to understand and not enough voters are impacted. 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. ___ time-nuts mailing 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
[time-nuts] cheap DVB-T USB dongles and HF digital mode reception
Further maybe even obtain better performance. But thats far from my concern right now. I simply want to get the systems back online to watch propagation behaviors as I have for years. (DVB-T dongles could excel at that.. automated digitally tuned reception..) I don't see how. The time transmitted will have the same propagation issues as the 60 kHz, so will be subject to diurnal variations plus ionospheric randomness. Maybe in the future there will be a $7 chip set that magically does whats been written by nist/John Lowe. Or like someone suggested we get the dtv tuner coupon. :-) Not likely. Did you mean the Realtek DVB-T dongles? well.. its hard to beat them for the money.. But they aren't a complete solution unless they are paired with a computer.. However, recently Leif, SM5BSZ, the author of Linrad, discovered a way to fully turn off the AGC.. that is a really great new development which makes them much more useful for measurement. http://www.nitehawk.com/sm5bsz/linuxdsp/hware/rtlsdr/rtlsdr.htm With an upconverter (like the one below) http://www.george-smart.co.uk/wiki/FunCube_Upconverter a nice digital receiver for 3 - 30 MHz (or the lower frequency bands) can be built for very little money.. They already handle VHF-UHF... As USB devices they need a USB host. Also application software like gnuradio or even linrad do require a decent powered CPU. But they do work okay with the $30 raspberrypi (700 MHz ARM) With the rtlsdr driver one can also output directly to a FIFO or TCP_IP, but something would have to process that to make use of that data.. Anyway, seeing the bit about the $7 coupon and suspecting that was what was being mentioned, I thought I should pass this info on.. They are what they are.. cheap devices.. kind of like those Sure GPS modules.. But nonetheless they are tons of fun and very useful in applications where all is needed is SOME way of receiving some signal cheaply, as long as you don't expect them to do much more than that.. Then, having shed any lofty expectations, you will be pleasantly surprised at what they can do. -Tofurk Could well be just an EPROM, but you need all the other stuff to support it... antenna, cables, power supply. A $7 will not be the end of it. YMMV, -John But it does truly seem possible to succeed on this. Maybe its our skills that are insufficient to pull this off. But I haven't given up at all. Just delayed with family... Can't wait to heat the soldering iron up late next week. ___ time-nuts mailing 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] Phase modulation detection/NIST plan
If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing 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] [OT]: HP-5061A and a dust bunny.....
This was such a crazy event that I have to share this with somebody. I started to notice an odd smell in the ham shack/lab yesterday night. Now we had a bad weather storm and was one of 2.5 Million homes without AC power for 5 days. So the generators were pressed into service and kept the lab cool with a 9,000BTU room air conditioner. My first thought was mold in the temporary A/C unit. But after the family came home from church it was very clear that it was much worse than a simple mold issue. It was the smell of a dead rodent. It had to be. I recognized it by then. So the hunt was on! Where was the dead mouse or mole that one of our cats must have dragged in through the pet door? The astute may already know the answer: In the bottom of a rack where an HP-5061A lives was not only the typical dust bunnies that often collect in such areas .BUT .. there was also a dead rabbit! BTW .All 3 cats have been interviewed and none will admit to being involved in any way. -Brian, WA1ZMS/4 Forest, VA ßwhere the AC mains are back on and the venting of the shack/lab continues with an outside air temp of 38C. No kidding! Whats worse the heat or the smell? Both will kill you. ___ time-nuts mailing 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] [OT]: HP-5061A and a dust bunny.....
I understand this event perfectly. Our feline owners leave us presents on an occasional basis. Usually we find them straight away, but when we can't, ninja nose wife takes over. For some reason, however, they tend to only leave the back half of the dead rabbit. My spouse says it is because the back half must taste like a$$. To make it time relevant, why is it the cats only bring things at precisely 4:30 AM? I'm pretty sure they are not WWV compliant. Thanks, On Jul 8, 2012, at 16:50, Brian, WA1ZMS wa1...@att.net wrote: This was such a crazy event that I have to share this with somebody. I started to notice an odd smell in the ham shack/lab yesterday night. Now we had a bad weather storm and was one of 2.5 Million homes without AC power for 5 days. So the generators were pressed into service and kept the lab cool with a 9,000BTU room air conditioner. My first thought was mold in the temporary A/C unit. But after the family came home from church it was very clear that it was much worse than a simple mold issue. It was the smell of a dead rodent. It had to be. I recognized it by then. So the hunt was on! Where was the dead mouse or mole that one of our cats must have dragged in through the pet door? The astute may already know the answer: In the bottom of a rack where an HP-5061A lives was not only the typical “dust bunnies” that often collect in such areas…….BUT…….. there was also a dead rabbit! BTW….All 3 cats have been interviewed and none will admit to being involved in any way. -Brian, WA1ZMS/4 Forest, VA ßwhere the AC mains are back on and the venting of the shack/lab continues with an outside air temp of 38C. No kidding! What’s worse the heat or the smell? Both will kill you. ___ time-nuts mailing 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] [OT]: HP-5061A and a dust bunny.....
They lie anyway. Hope you get your power back and not lose it again tonight. Regards, Tom - Original Message - From: Brian, WA1ZMS wa1...@att.net To: Time-Nuts time-nuts@febo.com Sent: Sunday, July 08, 2012 4:50 PM Subject: [time-nuts] [OT]: HP-5061A and a dust bunny. BTW….All 3 cats have been interviewed and none will admit to being involved in any way. ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Peter indeed there could be But it should not need to be decoded to undo the psk. Plus documentation lacks some of the details I think to actually do it. But that would be a significant project since the formats not been settled completely yet. Regards Paul. On 7/8/2012 6:40 PM, Peter Gottlieb wrote: Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Phase modulation detection/NIST plan
Hi Peter, That's be the hard way, but yes, if the message BPSK coded is computable and of a known format. If the message contained more than time, like solar flux, it gets more complicated very rapidly. A similar thing was done with the Equatorial system 30+ years ago. In that case, each data bit was broken into something like 32 or 64 chips (I don't remember). There were two maximally distant, orthogonal chip patterns, representing 1 and 0. The incoming BPSK message went through a 0 or 180 degree switch, then the IF stages. The switch was driven from a local (known pattern) chip generator, so that if everything was synced up the narrow band IF would put out the 0 or 1 that had been encoded. BTW, this trick vastly improved the system S/N becaust it narrowed the receiver IF bandwidth many times. If the chip pattern is not known (fixed) or computable (like a correct TOD) things go to pot quickly. Rather than building such a kludge, it would be easier to use the locked clock in a newly designed receiver and phase compare that to your local standard directly. -John == Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Phase modulation detection/NIST plan
Hi In this case the data format and it's contents are highly computable. If you have a good local clock *and* an initial lock, the rest of what follows is predictable. That of course assumes we know the real format …. Bob On Jul 8, 2012, at 6:58 PM, J. Forster wrote: Hi Peter, That's be the hard way, but yes, if the message BPSK coded is computable and of a known format. If the message contained more than time, like solar flux, it gets more complicated very rapidly. A similar thing was done with the Equatorial system 30+ years ago. In that case, each data bit was broken into something like 32 or 64 chips (I don't remember). There were two maximally distant, orthogonal chip patterns, representing 1 and 0. The incoming BPSK message went through a 0 or 180 degree switch, then the IF stages. The switch was driven from a local (known pattern) chip generator, so that if everything was synced up the narrow band IF would put out the 0 or 1 that had been encoded. BTW, this trick vastly improved the system S/N becaust it narrowed the receiver IF bandwidth many times. If the chip pattern is not known (fixed) or computable (like a correct TOD) things go to pot quickly. Rather than building such a kludge, it would be easier to use the locked clock in a newly designed receiver and phase compare that to your local standard directly. -John == Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Phase modulation detection/NIST plan
A risky assumption, and a cold start could be tricky. Equatorial took many minutes to lock up, with a much higher data rate, and it did it by slowly sweeping the local clock. Aside: That's why military spread spectrum systems like good local clocks. They lock up a whole lot faster that way. -John Hi In this case the data format and it's contents are highly computable. If you have a good local clock *and* an initial lock, the rest of what follows is predictable. That of course assumes we know the real format . Bob On Jul 8, 2012, at 6:58 PM, J. Forster wrote: Hi Peter, That's be the hard way, but yes, if the message BPSK coded is computable and of a known format. If the message contained more than time, like solar flux, it gets more complicated very rapidly. A similar thing was done with the Equatorial system 30+ years ago. In that case, each data bit was broken into something like 32 or 64 chips (I don't remember). There were two maximally distant, orthogonal chip patterns, representing 1 and 0. The incoming BPSK message went through a 0 or 180 degree switch, then the IF stages. The switch was driven from a local (known pattern) chip generator, so that if everything was synced up the narrow band IF would put out the 0 or 1 that had been encoded. BTW, this trick vastly improved the system S/N becaust it narrowed the receiver IF bandwidth many times. If the chip pattern is not known (fixed) or computable (like a correct TOD) things go to pot quickly. Rather than building such a kludge, it would be easier to use the locked clock in a newly designed receiver and phase compare that to your local standard directly. -John == Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing 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] Phase modulation detection/NIST plan
On 07/09/2012 12:46 AM, paul wrote: Peter indeed there could be But it should not need to be decoded to undo the psk. Plus documentation lacks some of the details I think to actually do it. But that would be a significant project since the formats not been settled completely yet. I have looked at the PTTI 2011 paper (wwvb.pdf) and much of a format is being shown. Has anyone established the 14 bit sync-word and verified the format? It seems that aligning up with the normal AM broadcast should be possible. Can someone record it as it has been reduced to say 2 kHz and analyze the produced audio file? Recoding with 48 kHz sampling rate should allow almost trivial 2 kHz I-Q demodulation to illustrate phase swaps. Cheers, Magnus ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul Are you getting at something along the lines of everything about the old system is a known quantity, and any error is just going to creep in at one point..the accuracy is easy to maintain using that system? The accuracy of the crystals on these cheap SDRs is terrible because temperature variations are severe in those little dongles as they warm up. Once their temps stabilize, most people use their drivers to enter in a ppm value that cancels the error out somewhat. Uncorrected the inaccuracy typically ranges from a few khz at 60 MHz to 40 or 50 KHz or more at 2200 Mhz. Also the dongles vary in the range of frequencies they can tune. Some of them will go, as I said, as high as 2207-2210 MHz. They don't cover the HF bands out of the box, but a few months back some adventurous people discovered that by feeding a HF signal directly into the RTL2832, bypassing the tuner chip, they can be made to tune the HF bands - at what is described as enough sensitivity to listen to shortwave, hams using SSB and CW. They can also be made to tune below the AM band, somehow. Its possible they could be modified with off the shelf parts to have quite respectable sensitivity and selectivity, even though they were not made to tune those bands.. Nobody with any decent test equipment has characterized this direct sampling mode's performance because most of the people who are playing with them simply don't have the equipment to aspire to such things.. but the fact seems striking to me that here is a device which until quite recently could be found for under $20 in retail environments that with quite minimal modifications could quite possibly function as both a multimode communications receiver over a very large chunk of the spectrum, sucking down up approximately a 2.6 to 3.2 MHz slice of spectrum at a time, or alternatively could function as a sort of poor mans spectrum analyzer.. Throw in the ability to use gnuradio which is a very sophisticated set of tools for communications engineering, and you have a situation where, since the cost of entry is so low, its not so unreasonable to devote some time to trying to grok some radio scheme and work with it to see what can be done. Digital radios are no less capable than analog radios, nor are the results achieved with them any less capable of being accurate. All the sources of error are quantifiable and probably those dongles are a situation where a small investment in replacing the crystal with a TCXO, air cooling or basic thermal management, calibration, etc, might pay off big in results very quickly. Already people are doing the kind of things that people do with expensive equipment with them, not $20 toys. So, there are just a load of possibilities with them. A way to see if this NIST format could be worked with would be to save a capture file of the broadcast signal to disk and then it would be possible to work with that offline later in gnuradio even when the transmitter was not broadcasting that kind of modulation. Its surprising that this broadcasting format has not been published as an open spec. Thats a whole other (important) issue right there. Anyway, I saw the discussion about this changeover and I thought the idea might seem like a crazy one but I think it could potentially work and keep the cost low. If these other issues could be dealt with. But I think they might be straightforward to deal with for you guys as its your area of expertise. When you have one of these finger-sized little things in your hand and you are fooling around with it, its pretty amazing. I say that as somebody who has been into radio ever since I was a very little kid. I am hard to impress with technology.. and this was pretty awesome. The misgivings were expressed in one of the earlier posts that this changeover was proceeding too rapidly and fears that technically it could create a captive market - Just like with the breakup of Ma Bell, competition is good.. and having some other options close at hand would keep everything more honest. (Unrelated, Just curious, did any of you guys ever live in Tarrytown NY?) Tofurk ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Hi The clocks we would be using are *much* better than what most military systems use…. I also *assume* that an initial lock up that takes a hour is perfectly acceptable in this application. You will still need a lot of hours / days / what ever of data to get useful stability off of WWVB, spending an hour or more to acquire from a cold start will have little net impact. Bob On Jul 8, 2012, at 7:29 PM, J. Forster wrote: A risky assumption, and a cold start could be tricky. Equatorial took many minutes to lock up, with a much higher data rate, and it did it by slowly sweeping the local clock. Aside: That's why military spread spectrum systems like good local clocks. They lock up a whole lot faster that way. -John Hi In this case the data format and it's contents are highly computable. If you have a good local clock *and* an initial lock, the rest of what follows is predictable. That of course assumes we know the real format …. Bob On Jul 8, 2012, at 6:58 PM, J. Forster wrote: Hi Peter, That's be the hard way, but yes, if the message BPSK coded is computable and of a known format. If the message contained more than time, like solar flux, it gets more complicated very rapidly. A similar thing was done with the Equatorial system 30+ years ago. In that case, each data bit was broken into something like 32 or 64 chips (I don't remember). There were two maximally distant, orthogonal chip patterns, representing 1 and 0. The incoming BPSK message went through a 0 or 180 degree switch, then the IF stages. The switch was driven from a local (known pattern) chip generator, so that if everything was synced up the narrow band IF would put out the 0 or 1 that had been encoded. BTW, this trick vastly improved the system S/N becaust it narrowed the receiver IF bandwidth many times. If the chip pattern is not known (fixed) or computable (like a correct TOD) things go to pot quickly. Rather than building such a kludge, it would be easier to use the locked clock in a newly designed receiver and phase compare that to your local standard directly. -John == Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Phase modulation detection/NIST plan
Hi The gotcha is that they may change the sync word based on test data. They may also tweak other vague points in the spec based on the troubles they run into in their tests or with their silicon. Bob On Jul 8, 2012, at 8:07 PM, Magnus Danielson wrote: On 07/09/2012 12:46 AM, paul wrote: Peter indeed there could be But it should not need to be decoded to undo the psk. Plus documentation lacks some of the details I think to actually do it. But that would be a significant project since the formats not been settled completely yet. I have looked at the PTTI 2011 paper (wwvb.pdf) and much of a format is being shown. Has anyone established the 14 bit sync-word and verified the format? It seems that aligning up with the normal AM broadcast should be possible. Can someone record it as it has been reduced to say 2 kHz and analyze the produced audio file? Recoding with 48 kHz sampling rate should allow almost trivial 2 kHz I-Q demodulation to illustrate phase swaps. Cheers, Magnus ___ time-nuts mailing 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] Phase modulation detection/NIST plan
If you have a deep fade every few hours or minutes, as is common, relock time becomes an issue. -John == Hi The clocks we would be using are *much* better than what most military systems use . I also *assume* that an initial lock up that takes a hour is perfectly acceptable in this application. You will still need a lot of hours / days / what ever of data to get useful stability off of WWVB, spending an hour or more to acquire from a cold start will have little net impact. Bob On Jul 8, 2012, at 7:29 PM, J. Forster wrote: A risky assumption, and a cold start could be tricky. Equatorial took many minutes to lock up, with a much higher data rate, and it did it by slowly sweeping the local clock. Aside: That's why military spread spectrum systems like good local clocks. They lock up a whole lot faster that way. -John Hi In this case the data format and it's contents are highly computable. If you have a good local clock *and* an initial lock, the rest of what follows is predictable. That of course assumes we know the real format . Bob On Jul 8, 2012, at 6:58 PM, J. Forster wrote: Hi Peter, That's be the hard way, but yes, if the message BPSK coded is computable and of a known format. If the message contained more than time, like solar flux, it gets more complicated very rapidly. A similar thing was done with the Equatorial system 30+ years ago. In that case, each data bit was broken into something like 32 or 64 chips (I don't remember). There were two maximally distant, orthogonal chip patterns, representing 1 and 0. The incoming BPSK message went through a 0 or 180 degree switch, then the IF stages. The switch was driven from a local (known pattern) chip generator, so that if everything was synced up the narrow band IF would put out the 0 or 1 that had been encoded. BTW, this trick vastly improved the system S/N becaust it narrowed the receiver IF bandwidth many times. If the chip pattern is not known (fixed) or computable (like a correct TOD) things go to pot quickly. Rather than building such a kludge, it would be easier to use the locked clock in a newly designed receiver and phase compare that to your local standard directly. -John == Any possibility of using the decoded signal to un-do the modulation and feed the reconstituted signal to the older receiver? On 7/8/2012 12:56 PM, paul wrote: Ei Sorry if I have your name reversed. By taking this approach it eliminates the ability to use wwvb as a frequency reference because it destroys that traceability. Thats what we are trying to preserve. Or at least re-establish for the older phase measuring receivers. Regards Paul On 7/8/2012 12:10 PM, Tofurk Ei wrote: If the changeover you are talking about is this one: http://www.nist.gov/pml/newsletter/radio.cfm as a proof of concept a DVB-T dongle/upconverter combo could almost certainly handle PM easily to output whatever it encodes, when paired with gnuradio.. The RTL2832U chip might also be able to handle some low band signals directly, using direct sampling. No upconverter. Regardless, then the data would be fed into gnuradio - the gnuradio developers GUI is called gnuradio companion It has a nifty way of doing this kind of thing, one builds a flow graph where the actual demodulation is simply laid out graphically and tested. When everything works to one's satisfaction the file is saved and it gets compiled - then it can run - its basically a python script. If the modulation scheme is public, I think you can be almost certain that gnuradio might be quite useful to rapidly design a tool to demodulate it. Perhaps very quickly. For the money, one really couldn't hope to beat the flexibility of this combination in any other manner. If I were interested in trying this I would join the gnuradio mailing list and ask there. Perhaps the answer is surprisingly simple. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to
Re: [time-nuts] Phase modulation detection/NIST plan
There is not an infinity of good sync words. A typical good sync word has a high positive autocorrelation when synced, sloping downwards monotonically. Thus the cross-correlation of the received word with a locally stored reference can be used to steer the loop using a small dither and a lock-in technique. -John Hi The gotcha is that they may change the sync word based on test data. They may also tweak other vague points in the spec based on the troubles they run into in their tests or with their silicon. Bob On Jul 8, 2012, at 8:07 PM, Magnus Danielson wrote: On 07/09/2012 12:46 AM, paul wrote: Peter indeed there could be But it should not need to be decoded to undo the psk. Plus documentation lacks some of the details I think to actually do it. But that would be a significant project since the formats not been settled completely yet. I have looked at the PTTI 2011 paper (wwvb.pdf) and much of a format is being shown. Has anyone established the 14 bit sync-word and verified the format? It seems that aligning up with the normal AM broadcast should be possible. Can someone record it as it has been reduced to say 2 kHz and analyze the produced audio file? Recoding with 48 kHz sampling rate should allow almost trivial 2 kHz I-Q demodulation to illustrate phase swaps. Cheers, Magnus ___ time-nuts mailing 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] Phase modulation detection/NIST plan
Could not the phase modulation be made +/-90 degrees, with the appropriate number of stuff bits being added so that the average phase remains constant? Would the older receivers simply average out the phase variation over a longer period? David GM8ARV -- 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] Phase modulation detection/NIST plan
On Sun, Jul 08, 2012 at 09:02:53PM -0400, Bob Camp wrote: Hi The gotcha is that they may change the sync word based on test data. They may also tweak other vague points in the spec based on the troubles they run into in their tests or with their silicon. I finally read the wwvb.pdf paper (yes, do so before opening mouth)... I think I read the Binary Phase Shift Keying Modulation paragraph on page 10 to indicate they are using ABSOLUTE, not differential BPSK. They refer to the baseband waveforms s0(t) and s1(t). To me this is the absolute I vector... and this clearly says that a 0 is always upward (or by convention in phase), and a one is always downward (180 out)... They clearly say the phase shift is 180 degrees... I would think this clearly could be phrased better... It appears the data format they propose is quite well defined in the paper, though they clearly indicate that a proposed extension is changing the barker code sync word for frames every so often so as to indicate a different frame type that might contain highly entropic (eg volatile and unpredictable) information of undefined character including a possible mechanism for sending arbitrary and completely apriori unpredictable bitstreams, though doubtless constrained by the hamming codes used for FEC/error detection and the barker code sync word. On a quick read it appears the complete 60 second time frame format is defined unambiguously. There are somewhat unpredictable DST bits and leap second bits in there... but in practice those change VERY infrequently from 60 second frame to frame or even from week to week or year to year. (Yes Congress likes to muck with DST every decade or so...). I am still reading more carefully, but I think this means that the entire phase and amplitude sequence of the signal is defined for the current initial version if you know the time of day and date and the current leap second and DST settings (which change VERY infrequently). And I *THINK* I understand this means the absolute phase sequence relative to the 60 KHz going into the modulator at the transmitter Thus the initial signal phase modulation could be removed by some comparatively simple itty bitty microp software driving a balanced modulator BUT future signal extensions might not have that property. As for acquiring bit sync with the signal, both the amplitude and phase information should allow a micro to do this easily and relatively quickly if the I vector were provided to the micro somehow. This would presumably be possible by either sampling the 60 KHz directly with an A/D (at 240 Ksample/sec) or by using an external balanced mixer driven by local synthesized 60 KHz. Even just an envelope detector would work with strong signals because of the AM component, and this might be enough to acquire adequate bit sync for some purposes. Software PLLs at 1 second rate are duck soup for even a SLOW micro... and frequency errors are tiny so tracking can be tight. And acquisition for these is also very fast given reasonable SNR. Only takes forever if SNR is so low it takes that many seconds correlation to see a reliable tick. I admit as I think about this that if one synthesized the clock for a itty bitty simple micro from say a local DUT 10 MHz whose phase relative to WWVB one is monitoring one could do much of the entire job by using programmable timers on the micro and its internal A/D. This includes phase error versus WWVB output and of course TOD output. One would almost certainly want to either use external balanced mixers (FET switches ?) and produce an analog I and Q (low pass filtered) for processing by a really slow micro or use a fast enough one to take a stream of actual real 60 KHz input samples at 240 KHz and compute filtered I and Q) (and LP filter/decimate it) (yes, with accurate A/D clocking from suitable microp output pin interval timers you might well be able to subsample by a lot and not actually ever deal with even any close to a 240 KHz sample stream with the micro). This would of course allow computation of the vector positions of the WWVB signal modulation in I and Q space relative to the 10 MHz clock from the DUT. And from that one should be able to compute the various moments of 10 MHz DUT clock drift and do a decent job of compensating for it (better and better as the DUT clock gets more stable/predictable) and ride out fairly long fades and outages without losing a pretty good idea of the expected WWVB phase. Presumably most standards whose phase one is tracking with such setups are very stable, thus the holdover should be considerable if one uses a good error and drift estimate to adjust ones local idea of WWVB phase relative to local clock derived from the standard to compensate. And guess what, determining a local error and drift estimate is precisely what such a system
