Re: [time-nuts] GPS SDR (was: FE-.5680A trimming resolution)
On Wed, 1 Feb 2012 09:27:30 -0800 Chris Albertson albertson.ch...@gmail.com wrote: I thought it might be interresting but then found out you need to buy $2,000+ worth of hardware for even start experimenting.Open Source SDR needs to run on a common affordable platform or it will never gain the critical mass of users that it take to make the project live longer then a few months. That's because the URSP is a general purpose system. It is designed to do many things. That makes it expensive. And being expensive, it has a low production volume, which makes it even more expensive. I think, a specialized GPS SDR can be build for less than 500 USD in low (a dozen at max) volumes. http://www.sparkfun.com/products/10981 -- 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] FE-.5680A trimming resolution
On Thu, 02 Feb 2012 00:50:39 +0100 Magnus Danielson mag...@rubidium.dyndns.org wrote: I have not seen any such papers yet. Do you have any pointers or hints what to search for? Let me see... yes, here it is: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA497270 Thanks! Printed and ready to be read :-) 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] GPS SDR
On Thu, 02 Feb 2012 01:22:07 +0100 Magnus Danielson mag...@rubidium.dyndns.org wrote: On 01/02/12 19:12, Attila Kinali wrote: I guestimate, that the RF/ADC part would cost somewhere between 100 to 200 USD in parts. The big uncertainty here is the FPGA. I have no clue how much logic space for a GPS SDR would be needed at minimum and how much would be desirable. Hence i have no guess what the FPGA would cost (could be anything from a cheap 20USD FPGA to a 300 USD one). That's why you start of with using an Ettus box as a boiler plate. Once you have working code, you can re-target it for a smaller device and situation. You can do dry synthesis towards the new platform without having it as a physical device. The basic design can still be running on that Ettus platform. Come to think of it, I did get a few university point on a 2-week coarse teaching exactly this point, spin on big-ass FPGA machines and then go to target. :) That's... 18 years ago. Time flies. Well.. i rather thought about doing a scilab model of the gps signals. Write the VHDL code, use ghdl to see whether it works correctly and then use one of those web eddition synthesizers to see how much space it uses. This way i already have working code when i get the hardware, don't have to buy any Ettus box and can still choose the right FPGA ;-) Front-end chips is still there. That's how they build these: http://ccar.colorado.edu/gnss/ http://www.sparkfun.com/products/8238 http://www.sparkfun.com/products/10981 That will suffice to get you started in the SDR field. Hmm.. the successor of the chip used there (the SE4150L) seems to be available in small quantities... That wasn't the case when i last looked. But it's limited to L1 C/A only and cannot even be modified for the P(Y) or Galileos E1 signal. The MAX2769 (mentioned by Tristan Steele) looks better in that regard. It can be configured to 8MHz BW, which is enough for E1 reception. Probably a degraded L1 P(Y) tracking could be implemented as well... 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] GPS SDR
On Thu, 2 Feb 2012 11:41:17 +1100 Tristan Steele tristan.ste...@gmail.com wrote: I have been looking at SDR GPS reception for a while, and have a number of ideas as to how to go about this process. My first point of call is the layout of a board using a MAX2769B (1) receiver chip attached directly to a Spartan 3E- 500 FPGA and then to a USB interface. I have decided to do this using an add-on board to the Papillio FPGA boards (2) that have been linked here before, incorporating the receiver chip, level shifters, power supplies, as well as a somewhat buffered SMA input for monitoring an external signal. The original board design requires an external reference oscillator for the MAX2769B, I am intending to operate it with a 10MHz signal to begin with. Heh.. I thought about using teh DE0-nano board from terasic for something similar.. but never got around to buy one.. Anyway, I will be happy to share progress as it occurs if anyone is interested? We are, of course, interested :-) 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] FE-.5680A trimming resolution
OK, got it: no need to lock the receiver clock to birds to get stable data (e.g. Oncore+Cs) but the clock can be locked to birds to get even better data and obtain for free a reference clock (TBolt). The use of a stable clock (not locked to birds) feeding the receiver can show the various errors that affect the downlink having removed the clock instabilities. On Thu, Feb 2, 2012 at 9:30 AM, Attila Kinali att...@kinali.ch wrote: On Thu, 02 Feb 2012 00:50:39 +0100 Magnus Danielson mag...@rubidium.dyndns.org wrote: I have not seen any such papers yet. Do you have any pointers or hints what to search for? Let me see... yes, here it is: http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA497270 Thanks! Printed and ready to be read :-) 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. ___ time-nuts mailing 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] FE5680 DDS plot
Great plot :) I've a dump of the SPI transfers during a night taken with the logic analyzer... but have found no time yet to process the dump to extract the transfers. Of course it is easier to take it from the serial port data :) The adjustment looks quite closely related to the temperature. Regards, Javier El 02/02/2012 06:15, Scott Newell escribió: Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! ___ time-nuts mailing 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] FE5680 DDS plot
I forgot... have you had the opportunity to check if the difference between the two DDS programming words is the same in all cases? All my readings leds to 1400.00x Hz, I've not looked at it but probably the difference in DDS counts is constant. Regards, Javier El 02/02/2012 10:13, Javier Herrero escribió: Great plot :) I've a dump of the SPI transfers during a night taken with the logic analyzer... but have found no time yet to process the dump to extract the transfers. Of course it is easier to take it from the serial port data :) The adjustment looks quite closely related to the temperature. Regards, Javier El 02/02/2012 06:15, Scott Newell escribió: Javier Herrero's exciting DDS discovery led to this plot of the unit tweaking the frequency (cmd 0x22): http://n5tnl.com/time/fe-5680a/graphs/dds_autotuning.png It appears to make an adjustment even before lock! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier Herrero Chief Technology Officer EMAIL: jherr...@hvsistemas.com HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.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] GPS SDR
On Wed, 01 Feb 2012 21:53:16 -0800 Jim Lux jim...@earthlink.net wrote: You don't need the ADC: you just need a limiter/comparator. Yes, but this degrades sensitivity quite a lot. You don't need insane sampling rates. Think in terms of subharmonic sampling. This requires that you have an ADC that has the anlog bandwidth of the signal. And ADCs with a analog BW in the GHz range are damn expensive and hard to get. Also a problem is to get the sampling frequency right if you want to sample more than one band. Downmixing solves both of these problems at the cost of higher complexity and a bit more noise. Is there a publically-available antenna design that's easy to fabricate, has a stable phase center, covers 1100--1600 MHz, and has a good pattern over this band with low cross-polarization? Even a large choke-ring design would be okay if it's fully specified. I think there are some crossed dipole designs around. What about quad helix? Crossed dipole are narrow band and not easy to build as dual band designs at least at those frequencies. Quad helix needs quite a precision to get the right frequency and dual band designs (stacked helixes) get even more difficult. 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] ANFSCD - Synchronizing time in home video recorders
I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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.
[time-nuts] GPS receiver vs local oscillator
If I want to decode a GPS signal, do I have to know (or figure out) the frequency of the local oscillator? Or does it drop out of the calculations, somehow? -- 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] FE-5680A programming connector pinout
Thanks guys! Updated Elio's picture with the additional info John provided. Revised picture posted here... http://www.xertech.net/FE5680A/FE-5680A_annotated_2.jpg Let me know if I got anything wrong. Elio, feel free to update your original if you want to keep control of it. -Rex On 2/1/2012 10:39 PM, John Beale wrote: http://www.rhodiatoce.com/pics/time-nuts/FE-5680A_annotated.jpg Excellent work! I look forward to any further info. Great picture with the pins and some parts labelled. By the way, if you want you could add the frequencies going into and out of the Xilinx XC9572XL CPLD part: Pin 64: 60 MHz in from VCXO Pin 1: 20 MHz out to AD9832 DDS chip Pin 22: 30 MHz out Pin 49: 10 MHz out to sine shaping network See also: https://plus.google.com/photos/109928236040342205185/albums/5680473650837554113/5685304134718133138 It might clarify things to point out the 60 MHz through-hole crystal pins visible immediately below the MMBV432 varactor diode. Knowing that's the varactor, and looking at the circuit I'm guessing the VCXO tuning voltage must pass through the 10K resistor next to mini-coax connector J8 (then past the bypass cap, through the 1.0 uH inductor, to the diode). That 10k connects through a 1k to pin 8 (output 3) of the TLC27M4B quad opamp on the other side of the board, near the 60 MHz xtal. Hmm sure enough: at startup, pin 8 swings between 0 and 11.9V, before the unit locks, which in my case happens at 7.3 Volts. (The opamp is powered from a 13.16V supply, output swings typ. 1.3V below the + rail.) Just for fun, here's a plot of the VCXO tuning voltage at startup: https://picasaweb.google.com/109928236040342205185/FE5680A#5704421825887557874 ___ time-nuts mailing 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] FE 5680A purchase warning
ggg*fitting has two listings NEW and USED. Bought a NEW hoping to get a better unit. Based on tests unit has run at least three years. Also has dent on case.Recommend we stay away from this one. Is a marketing ploy. Will ship it back to day. There are other choices out there. Do not need to support fraudulent listings. Bert Kehren ___ time-nuts mailing 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] FE-5680A programming connector pinout
I modified my previous pinout image adding some more info (thanks to John and Rex for their suggestions): you can find them at the following addresses: JPG format (1.4MB): http://www.rhodiatoce.com/pics/time-nuts/FE-5680A/FE-5680A_annotated_001.jpg Editable Adobe photoshop format (40MB): http://www.rhodiatoce.com/pics/time-nuts/FE-5680A/FE-5680A_annotated_001.psd Whole PCB, bottom view (4.2MB) at 1200dpi resolution (3878x5853px): http://www.rhodiatoce.com/pics/time-nuts/FE-5680A/FE-5680A_BottomView.jpg If needed, I can put higher resolution images of the PCB: I will try to prepare a picture of the other side of the PCB, but I have to check if I am able to disassemble the FE-5680A PCB without any damage... Let me know if you need them. I would like to have a dead FE-5680A to strip its main components and getting a more detailed view of the connections between the logical parts (CPU/Memory/CPLD). Any offers? - - - - - - - Other findings: the connection between the CPU (*DS80C323END*) and the external memory chip (*PSD813F1V-20UI) is exactly the one described on Figure 23 at page 47 in the PSD datasheet http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00024482.pdf . _ Elio Corbolante. * ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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. ___ time-nuts mailing 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] Info request for some FEI modules
Hello all, I have acquired some FEI modules that have seen better days, but look like they might be repairable. I've looked in the ko4bb and BAMA manuals archives without success - is there any chance anyone on the list has any information on these units please? FE-1050-D Frequency Time Standard FE-350A Battery Power Supply Module FE-150A DTF-Module (Can replies be direct to me please, to save annoying everyone on the list.) Thank you, Peter Vince (London, England) ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
I would disagree. The traffic on the FE-5680A took some of the group's bandwidth only in the recent weeks in coincidence with the appearance of cheap units on the auction site. Why to force time-nuts to jump to and fro one group and another? I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and there use and modification. This seems like the most popular subject and takes up allot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. ___ time-nuts mailing 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] TM 5680-0211 for 5680A series Rubidiums
You are welcome to upload it to my manuals pages www.ko4bb.com/manuals Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Bob Bownes bow...@gmail.com Sender: time-nuts-boun...@febo.com Date: Wed, 1 Feb 2012 12:41:19 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] TM 5680-0211 for 5680A series Rubidiums If someone sends me the manual, I have a location I can host it. Bob On Wed, Feb 1, 2012 at 12:38 PM, Larry McDavid lmcda...@lmceng.com wrote: I wish Rob Kimberley's email address had been preserved so I could also ask for this manual pdf file without adding traffic to TimeNuts. Chris Albertson offered to post the manual on-line to simplify this. I hope that is arranged by someone! However it be available, I want a copy of the 5680A series Technical Manual. -- Best wishes, Larry McDavid W6FUB Anaheim, CA (20 miles southeast of Los Angeles, near Disneyland) __**_ 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. ___ time-nuts mailing 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] Building a GPSDO trouble using Jupiter-T
Magnus, How do they compare in price to the receivers we normally use for timing? Do you see any advantage for a timing receiver to fix faster than once per second? Didier KO4BB Sent from my BlackBerry Wireless thingy while I do other things... -Original Message- From: Magnus Danielson mag...@rubidium.dyndns.org Sender: time-nuts-boun...@febo.com Date: Tue, 31 Jan 2012 20:50:39 To: time-nuts@febo.com Reply-To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] Building a GPSDO trouble using Jupiter-T On 31/01/12 03:17, Didier Juges wrote: You have to spend good money to get a GPS receiver capable of calculating it's time and/or position more than once per second. I am not aware of that being done for timing applications, but it is available for navigation GPS receivers, such as those used to track race cars (for a race car, one second is an eternity). I have seen navigation receivers capable of 10 fixes/second, I am sure there are better ones yet. They cost a lot of money. I have receivers which can run navigation solutions up to 10 times per second and raw-data results up to 50 times per second, I just don't have that neat options in it. Ah well. Double-frequency never the less. 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] New Rubidium Frequency Standard Group
I would disagree. The traffic on the FE-5680A took some of the group's bandwidth only in the recent weeks in coincidence with the appearance of cheap units on the auction site. Why to force time-nuts to jump to and fro one group and another? And some of us will not use yahoo lists, based on prior bad experiences. 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] New Rubidium Frequency Standard Group
Me too. I think that this is a transient that will surely decay... and that also is leading to several constructive sub-threads that are not directly related with the FE-5680A but nevertheless very interesting and very time-nut related. I'm not interested to subscribe another list that probably will became without activity quite soon. Regards, Javier El 02/02/2012 15:27, iov...@inwind.it escribió: I would disagree. The traffic on the FE-5680A took some of the group's bandwidth only in the recent weeks in coincidence with the appearance of cheap units on the auction site. Why to force time-nuts to jump to and fro one group and another? I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and there use and modification. This seems like the most popular subject and takes up allot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
No new groups please, the Rb thread is interesting for time-nuts, and I don't see the need. 73 - Marco IK1ODO ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
I dont want to have to take loads of groups to keep up with the expertise available on this Group. The answer to bandwidth in my case is the DELETE key, and it would be less if there was not the continued use of quoted-quoted quotes :-)) Even if you quote one its worth knocking the tail off because it will pick up another one. Even though I am not likely to buy that Rb system I saved the first few messages because I might come across one. The Re messages then get deleted without reading. in the vain hope that no-one has hijacked the subject! I may be just getting to be a cynical old man but I have the feeling that Group spawning is an ego thing Alan G3NYK - Original Message - From: Rich (Buckeye) kq...@bex.net To: time-nuts@febo.com Sent: Thursday, February 02, 2012 1:57 PM Subject: [time-nuts] New Rubidium Frequency Standard Group I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and there use and modification. This seems like the most popular subject and takes up allot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. Tnx ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
I created a spam filter for anything with 5680 so I don't see all those posts. On 02/02/2012 08:57 AM, Rich (Buckeye) wrote: I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
I indeed created a filter to send them to another folder so I keep both and have all about the 5680A grouped. On 02/02/2012 16:07, Mike Naruta AA8K wrote: I created a spam filter for anything with 5680 so I don't see all those posts. On 02/02/2012 08:57 AM, Rich (Buckeye) wrote: I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the ___ time-nuts mailing 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] GPS receiver vs local oscillator
On 2/2/12 1:49 AM, Hal Murray wrote: If I want to decode a GPS signal, do I have to know (or figure out) the frequency of the local oscillator? Or does it drop out of the calculations, somehow? Yes, it comes out in the calculations. That's why you need 4 satellites. You solve for x,y,z and local clock offset. (and, in reality you also have to solve for xdot,ydot,zdot, and fdot) If you have a stationary receiver, or a known position, then you have an additional constraint or two you can fold into the solution, so you don't need as many observables. ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
Hi Roberto, The motivation for this, I assume most list members know, is to drive cheap quartz stepper motor clocks with precise 32 kHz frequency, one derived from an atomic or GPS 10 MHz. The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary leap year algorithm to adjust the digital output phase to be as close as possible to the ideal 32.768 kHz phase on each cycle and also to have zero long-term error. I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. With non-integral ratios like this case, or without external analog components (e.g., PLL), it seems some level of jitter is always unavoidable. So the goal was to make it as mathematically small as possible, and furthermore, to be able to do the math within a half cycle, which is only 15 microseconds. I'll send you an early draft of the PIC code; the version that was most clear before I had to pinch too many cycles and added too many features. Let me know what you think. I also simulated the algorithm on a PC and measured the ADEV and phase noise. That simulation code is file 10m32k.c under: http://www.leapsecond.com/tools/ /tvb - Original Message - From: Roberto Barrios rbarri...@msn.com To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 02, 2012 5:09 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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] GPS SDR
On 2/2/12 1:28 AM, Attila Kinali wrote: On Wed, 01 Feb 2012 21:53:16 -0800 Jim Luxjim...@earthlink.net wrote: You don't need the ADC: you just need a limiter/comparator. Yes, but this degrades sensitivity quite a lot. You don't need insane sampling rates. Think in terms of subharmonic sampling. This requires that you have an ADC that has the anlog bandwidth of the signal. And ADCs with a analog BW in the GHz range are damn expensive and hard to get. Also a problem is to get the sampling frequency right if you want to sample more than one band. Downmixing solves both of these problems at the cost of higher complexity and a bit more noise. Yes, if you need lots o'bits, but a single bit sampler with wide bandwidth is easy (which is why they do it). It's basically a D-latch at the end of the amplifier/limiter chain. There is a sampling rate around 38-39 MHz that works out nicely for all three bands (actually, any rate in that range probably works..I haven't looked).. It helps that the 3 GPS frequencies are related to a common base. A few minutes work with an Excel spreadsheet trying frequencies will probably find something that works: You want the carrier to alias to about a quarter of the sample rate (so the entire signal is in the sample bandwidth without aliasing), but not exactly in the center (because having some known frequency offset means your Doppler tracking doesn't have to go through zero) 40MHz gives you a sample bandwidth of 20 MHz, so you could probably sample slower, but I think having more samples/chip makes the tracking easier (if nothing else, oversampling is like having more bits in your ADC) Is there a publically-available antenna design that's easy to fabricate, has a stable phase center, covers 1100--1600 MHz, and has a good pattern over this band with low cross-polarization? Even a large choke-ring design would be okay if it's fully specified. I think there are some crossed dipole designs around. What about quad helix? Crossed dipole are narrow band and not easy to build as dual band designs at least at those frequencies. Quad helix needs quite a precision to get the right frequency and dual band designs (stacked helixes) get even more difficult. I suspect that you're right.. the actual antenna may be simple, the design is hard. The antennas we use for multiband look like a crossed dipole on the surface of a hemisphere, but the actual elements are a very odd shape: generally a wide strip, but there are some lumps and bumps in the outline. I'm going to guess that they were designed with some FEM code, and then iterated by hand. If you knew the shapes, it would be pretty easy to build, though: copper foil tape on an appropriate substrate. As you note, precision is important. I'd go hunting through patents assigned to Dorne Margolin. (part of EDO, these days, I think). Or even maybe looking at their datasheets. There's also what they call the helibowl antenna which is some form of helix in a bowl shaped reflector/ground plane. googling that might turn up something. ___ time-nuts mailing 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] FE-5680A 1 pps photo
I managed to take a photo at the scope screen showing the 1 pps pulse from an old FE-5680A (the one that does not need the 5V and does not output the oscillator signal - just the 1pps). Exposure was 30 sec, F9. The signal was barely visible with naked eye, and some jittering is present. The room of course was in complete darkness, but the reflex of the stand-by led of another instrument can be seen... 73 Alberto I2PHD http://dl.dropbox.com/u/15089947/1pps.gif ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
If anyone wants all the FE5580A mail to go to one place make a filter in you email reader. Tell it to place anything sent from the TN list with FE5680 in the hearer or text to go into a special folder or otherwise be tagged as fe5680 related. I think this happens all the time -- people talk about whatever is new. Eventually $40 fe5680s will not be new. On Thu, Feb 2, 2012 at 5:57 AM, Rich (Buckeye) kq...@bex.net wrote: I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and there use and modification. This seems like the most popular subject and takes up allot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. Tnx ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
Amazing... there is always something to learn from TVB. Now I'll try to derive a 2.048MHz G.703-13 clock from a 10MHz clock. I suspect that the procedure is similar, even if 2048KHz is not quite a power of 2. On Thu, Feb 2, 2012 at 4:35 PM, Tom Van Baak t...@leapsecond.com wrote: Hi Roberto, The motivation for this, I assume most list members know, is to drive cheap quartz stepper motor clocks with precise 32 kHz frequency, one derived from an atomic or GPS 10 MHz. The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary leap year algorithm to adjust the digital output phase to be as close as possible to the ideal 32.768 kHz phase on each cycle and also to have zero long-term error. I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. With non-integral ratios like this case, or without external analog components (e.g., PLL), it seems some level of jitter is always unavoidable. So the goal was to make it as mathematically small as possible, and furthermore, to be able to do the math within a half cycle, which is only 15 microseconds. I'll send you an early draft of the PIC code; the version that was most clear before I had to pinch too many cycles and added too many features. Let me know what you think. I also simulated the algorithm on a PC and measured the ADEV and phase noise. That simulation code is file 10m32k.c under: http://www.leapsecond.com/tools/ /tvb - Original Message - From: Roberto Barrios rbarri...@msn.com To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 02, 2012 5:09 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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. ___ time-nuts mailing 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] FE-5680A 1 pps photo
and here's another photo of the pulse from one of the newer breed of FE-5680A that require the 5V. Taken with a Sony Cybershot H5, 8 sec exposure, 'scope is an elderly Tektronix 2252 http://dl.dropbox.com/u/1690159/1PPS_1%20FE-5680E.jpg John H. On 2 Feb 2012, at 15:50, Alberto di Bene wrote: I managed to take a photo at the scope screen showing the 1 pps pulse from an old FE-5680A (the one that does not need the 5V and does not output the oscillator signal - just the 1pps). Exposure was 30 sec, F9. The signal was barely visible with naked eye, and some jittering is present. The room of course was in complete darkness, but the reflex of the stand-by led of another instrument can be seen... 73 Alberto I2PHD http://dl.dropbox.com/u/15089947/1pps.gif ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and there use and modification. This seems like the most popular subject and takes up allot of the group's bandwidth. Hi Rich, Welcome to the group. Clock performance looks different short-term, long-term, and many terms in between. There are a number of statistical tools that are used to measure stability. It is often the case that the performance of an oscillator over seconds is quite different from its performance over hours or days. Clocks also exhibit phase shifts and frequency jumps; white noise and random walk. Long-term drift. Then there are GPS disciplined oscillators. ADEV plots neatly sums up the character of an oscillator. This mailing list, also, has a certain character. There are jumps and shifts. There is some noise. To fully appreciate how good the group is you need to sample it for longer. A couple of months at least. Over several years you may even be able to measure drift. And although the time constant may be slow the list can be steered. If the Rb thread gets too out of hand, or gets too far off-topic some gentle hands will come in and pull it back on frequency. Meanwhile, enjoy the discussion. A great deal of interesting detail is emerging. A number of members who have been quiet are now contributing nicely. Creative ideas are emerging. So please stick around. Over time you will learn a lot here. /tvb www.leapsecond.com/time-nuts.htm ___ time-nuts mailing 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] FE-5680A 1 pps photo
Odd. Did Tektronix mark it Fluke PM3082? :) It is nice to know that the current generation of digital cameras can be used for this application. It is too bad that the image has so much noise. On Thu, 2 Feb 2012 16:27:03 +, John Howell j...@howell61.f9.co.uk wrote: and here's another photo of the pulse from one of the newer breed of FE-5680A that require the 5V. Taken with a Sony Cybershot H5, 8 sec exposure, 'scope is an elderly Tektronix 2252 http://dl.dropbox.com/u/1690159/1PPS_1%20FE-5680E.jpg On 2 Feb 2012, at 15:50, Alberto di Bene wrote: I managed to take a photo at the scope screen showing the 1 pps pulse from an old FE-5680A (the one that does not need the 5V and does not output the oscillator signal - just the 1pps). Exposure was 30 sec, F9. The signal was barely visible with naked eye, and some jittering is present. The room of course was in complete darkness, but the reflex of the stand-by led of another instrument can be seen... http://dl.dropbox.com/u/15089947/1pps.gif ___ time-nuts mailing 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] New Rubidium Frequency Standard Group
Staying on the topic of the thread, I also found the list clogging up with fixes for a cheap rubidium device (wouldn't call it a standard). Outlook told me that there were 10,350 messages in the time-nuts folder since it was archived at the end of 2010. I used Find for 5680 and got 900 messages, starting with Feb 2011 warnings about their frequency errors. Then I used Select All and Delete to remove 9% of the folder. How about a new list for eBay finds that are a waste of money, like the Lucent XO and Rb 15 MHz boxes? Maybe time-rats or time-junk Bill Hawkins Tobacco, coffee, alcohol, hashish, strychnine, are weak dilutions; the surest poison is time. Ralph Waldo Emerson, Jan 1862 -Original Message- From: Chris Albertson Sent: Thursday, February 02, 2012 10:03 AM If anyone wants all the FE5580A mail to go to one place make a filter in your email reader. Tell it to place anything sent from the TN list with FE5680 in the header or text to go into a special folder or otherwise be tagged as fe5680 related. I think this happens all the time -- people talk about whatever is new. Eventually $40 fe5680s will not be new. On Thu, Feb 2, 2012 at 5:57 AM, Rich (Buckeye) kq...@bex.net wrote: I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and their use and modification. This seems like the most popular subject and takes up a lot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. Tnx ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
Azelio, 2.048 MHz has a cycle period of just 488.28125 ns so a PIC/AVR is (far) too slow to use the same trick I did on the low frequency 32 kHz. I think you'll have to use a PLL for that one. How about a 16 kHz compare rate: 10 MHz / 625 = 16000 Hz = 2.048 MHz / 128 /tvb - Original Message - From: Azelio Boriani To: Tom Van Baak ; Discussion of precise time and frequency measurement Sent: Thursday, February 02, 2012 8:18 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Amazing... there is always something to learn from TVB. Now I'll try to derive a 2.048MHz G.703-13 clock from a 10MHz clock. I suspect that the procedure is similar, even if 2048KHz is not quite a power of 2. On Thu, Feb 2, 2012 at 4:35 PM, Tom Van Baak t...@leapsecond.com wrote: Hi Roberto, The motivation for this, I assume most list members know, is to drive cheap quartz stepper motor clocks with precise 32 kHz frequency, one derived from an atomic or GPS 10 MHz. The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary leap year algorithm to adjust the digital output phase to be as close as possible to the ideal 32.768 kHz phase on each cycle and also to have zero long-term error. I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. With non-integral ratios like this case, or without external analog components (e.g., PLL), it seems some level of jitter is always unavoidable. So the goal was to make it as mathematically small as possible, and furthermore, to be able to do the math within a half cycle, which is only 15 microseconds. I'll send you an early draft of the PIC code; the version that was most clear before I had to pinch too many cycles and added too many features. Let me know what you think. I also simulated the algorithm on a PC and measured the ADEV and phase noise. That simulation code is file 10m32k.c under: http://www.leapsecond.com/tools/ /tvb - Original Message - From: Roberto Barrios rbarri...@msn.com To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 02, 2012 5:09 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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. ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
Yes, shortly after having sent out the message I realized that I was, as usual, too fast. I'm aware that a simple microprocessor can't be used but a Spartan3 can be involved. Then another problem: the 2.048MHz is about 1/5 of the 10MHz so it is not possible. Sofar the way out is: dividing the 10MHz by 625 and then multiplying by 128 using the DCM in the Spartan3... but nothing clever in this method. Sorry, not a valid contribution. On Thu, Feb 2, 2012 at 6:07 PM, Tom Van Baak t...@leapsecond.com wrote: Azelio, 2.048 MHz has a cycle period of just 488.28125 ns so a PIC/AVR is (far) too slow to use the same trick I did on the low frequency 32 kHz. I think you'll have to use a PLL for that one. How about a 16 kHz compare rate: 10 MHz / 625 = 16000 Hz = 2.048 MHz / 128 /tvb - Original Message - From: Azelio Boriani To: Tom Van Baak ; Discussion of precise time and frequency measurement Sent: Thursday, February 02, 2012 8:18 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Amazing... there is always something to learn from TVB. Now I'll try to derive a 2.048MHz G.703-13 clock from a 10MHz clock. I suspect that the procedure is similar, even if 2048KHz is not quite a power of 2. On Thu, Feb 2, 2012 at 4:35 PM, Tom Van Baak t...@leapsecond.com wrote: Hi Roberto, The motivation for this, I assume most list members know, is to drive cheap quartz stepper motor clocks with precise 32 kHz frequency, one derived from an atomic or GPS 10 MHz. The 10 MHz to 32 kHz PIC divider I wrote uses a sort of binary leap year algorithm to adjust the digital output phase to be as close as possible to the ideal 32.768 kHz phase on each cycle and also to have zero long-term error. I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. With non-integral ratios like this case, or without external analog components (e.g., PLL), it seems some level of jitter is always unavoidable. So the goal was to make it as mathematically small as possible, and furthermore, to be able to do the math within a half cycle, which is only 15 microseconds. I'll send you an early draft of the PIC code; the version that was most clear before I had to pinch too many cycles and added too many features. Let me know what you think. I also simulated the algorithm on a PC and measured the ADEV and phase noise. That simulation code is file 10m32k.c under: http://www.leapsecond.com/tools/ /tvb - Original Message - From: Roberto Barrios rbarri...@msn.com To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 02, 2012 5:09 AM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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. ___ time-nuts mailing 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] GPS SDR
On Thu, 02 Feb 2012 07:49:53 -0800 Jim Lux jim...@earthlink.net wrote: [Limiting / Downmixing converter] Yes, if you need lots o'bits, but a single bit sampler with wide bandwidth is easy (which is why they do it). It's basically a D-latch at the end of the amplifier/limiter chain. Yes, but you lose IIRC about 3dB of performance compared to a 2bit ADC. There is a sampling rate around 38-39 MHz that works out nicely for all three bands (actually, any rate in that range probably works..I haven't looked).. It helps that the 3 GPS frequencies are related to a common base. Only if you sample them seperately. Which requires seperate, sharp filters for all of them. Also something that isn't that easy to do. Also do not forget that Galileo E1 signals have about a 20MHz Bandwidth. The combined E5 frequencies have about 50MHz. I think i've read somewhere that you can get away with 8MHz for the E1 signal. Don't know how the E5 behaves if you limit its bandwith. 40MHz gives you a sample bandwidth of 20 MHz, so you could probably sample slower, but I think having more samples/chip makes the tracking easier (if nothing else, oversampling is like having more bits in your ADC) Yes. [Antennas] Crossed dipole are narrow band and not easy to build as dual band designs at least at those frequencies. Quad helix needs quite a precision to get the right frequency and dual band designs (stacked helixes) get even more difficult. I suspect that you're right.. the actual antenna may be simple, the design is hard. The antennas we use for multiband look like a crossed dipole on the surface of a hemisphere, but the actual elements are a very odd shape: generally a wide strip, but there are some lumps and bumps in the outline. I thought about combining an antenna simulator with a genetic algo to see whether it produces any usable shapes. But i havent had time for this yet (and it's actually way down in my priority list). I'm going to guess that they were designed with some FEM code, and then iterated by hand. If you knew the shapes, it would be pretty easy to build, though: copper foil tape on an appropriate substrate. As you note, precision is important. That's why i said that probably a patch antenna build out of PCBs is the best solution. You can get the copper sheet at 0.1mm precision which would define frequency and polarity properties quite well. The only thing that would have to be done by hand would be the distance from the ground plate. I guestimate that this value is not as critical and that 0.5mm variation should be ok. I'd go hunting through patents assigned to Dorne Margolin. (part of EDO, these days, I think). Or even maybe looking at their datasheets. There's also what they call the helibowl antenna which is some form of helix in a bowl shaped reflector/ground plane. googling that might turn up something. From my understanding of antenna theory (which is very little), these are mostly variations on the directivity characteristic (ie to get a more favorable distribution), but do not change much the frequency characteristics. Ie if you don't have the frequency characteristics right with a straight design, there wont be much chance to get them right with a shaped design. 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] New Rubidium Frequency Standard Group
My frustration is that there is very little information or discussion as to the performance of the device, ultimately some may want to use it in their shop as thee reference, and to make that possible more performance data would be nice. It may be the best they have. Bert Kehren In a message dated 2/2/2012 11:44:28 A.M. Eastern Standard Time, b...@iaxs.net writes: Staying on the topic of the thread, I also found the list clogging up with fixes for a cheap rubidium device (wouldn't call it a standard). Outlook told me that there were 10,350 messages in the time-nuts folder since it was archived at the end of 2010. I used Find for 5680 and got 900 messages, starting with Feb 2011 warnings about their frequency errors. Then I used Select All and Delete to remove 9% of the folder. How about a new list for eBay finds that are a waste of money, like the Lucent XO and Rb 15 MHz boxes? Maybe time-rats or time-junk Bill Hawkins Tobacco, coffee, alcohol, hashish, strychnine, are weak dilutions; the surest poison is time. Ralph Waldo Emerson, Jan 1862 -Original Message- From: Chris Albertson Sent: Thursday, February 02, 2012 10:03 AM If anyone wants all the FE5580A mail to go to one place make a filter in your email reader. Tell it to place anything sent from the TN list with FE5680 in the header or text to go into a special folder or otherwise be tagged as fe5680 related. I think this happens all the time -- people talk about whatever is new. Eventually $40 fe5680s will not be new. On Thu, Feb 2, 2012 at 5:57 AM, Rich (Buckeye) kq...@bex.net wrote: I have only been a member of the time-nuts group for a short while. It seems like 75% of the posts here have to do with the FE-5680A Rubidium Frequency Standards and their use and modification. This seems like the most popular subject and takes up a lot of the group's bandwidth. There is a new Yahoo Group called Rubidium that just was recently started. I wonder if all the Rubidium traffic and posts would be better at that group. Send posts to : rubi...@yahoogroups.com Just a suggestion. Tnx ___ time-nuts mailing 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] FE-5680A 1 pps photo
Not odd but my mistake, I took a picture on both 'scopes and the Fluke gave marginally better results, the text referred to the wrong one. Sorry for the confusion. On 2 Feb 2012, at 16:43, David wrote: Odd. Did Tektronix mark it Fluke PM3082? :) It is nice to know that the current generation of digital cameras can be used for this application. It is too bad that the image has so much noise. On Thu, 2 Feb 2012 16:27:03 +, John Howell j...@howell61.f9.co.uk wrote: and here's another photo of the pulse from one of the newer breed of FE-5680A that require the 5V. Taken with a Sony Cybershot H5, 8 sec exposure, 'scope is an elderly Tektronix 2252 http://dl.dropbox.com/u/1690159/1PPS_1%20FE-5680E.jpg On 2 Feb 2012, at 15:50, Alberto di Bene wrote: I managed to take a photo at the scope screen showing the 1 pps pulse from an old FE-5680A (the one that does not need the 5V and does not output the oscillator signal - just the 1pps). Exposure was 30 sec, F9. The signal was barely visible with naked eye, and some jittering is present. The room of course was in complete darkness, but the reflex of the stand-by led of another instrument can be seen... http://dl.dropbox.com/u/15089947/1pps.gif ___ time-nuts mailing 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] 32768 Hz from 10 MHz
Hi Roberto: By changing the timer count dynamically it's possible to lower the jitter to one timer count. See: http://www.prc68.com/I/PClock.shtml#BA Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html Roberto Barrios wrote: Hi Tom, I'm interested in that divider. Actually, insterested in knowing how it works, not in the .HEX file. Breseham's algorith works but has inherent jitter and I've found no other solutions for situations like that. I'd live to know how it is done. Thank you, Roberto EB4EQA http://www.rbarrios.com -Mensaje original- From: Tom Van Baak Sent: Thursday, February 02, 2012 10:34 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders I think I've seen comments about making 32 KHz from 10 MHz in a PIC or AVR. tvb has this web page, but I don't see a 32 KHz option: http://www.leapsecond.com/pic/picdiv.htm Hal, Yes, I have a PIC divider that takes 5 or 10 MHz input and outputs a 32.768 kHz square wave with minimal jitter and no long-term phase offset. Contact me off-line if interested. /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. ___ time-nuts mailing 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] GPS receiver vs local oscillator
If I want to decode a GPS signal, do I have to know (or figure out) the frequency of the local oscillator? Or does it drop out of the calculations, somehow? Yes, it comes out in the calculations. That's why you need 4 satellites. You solve for x,y,z and local clock offset. (and, in reality you also have to solve for xdot,ydot,zdot, and fdot) Thanks. I thought the 4th satellite was needed to determine the time. Wouldn't it take a 5th satellite to also determine the frequency of the local clock? -- 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] GPS receiver vs local oscillator
On Thu, 02 Feb 2012 10:49:22 -0800 Hal Murray hmur...@megapathdsl.net wrote: Yes, it comes out in the calculations. That's why you need 4 satellites. You solve for x,y,z and local clock offset. (and, in reality you also have to solve for xdot,ydot,zdot, and fdot) I thought the 4th satellite was needed to determine the time. Wouldn't it take a 5th satellite to also determine the frequency of the local clock? Not really. There are two ways to get the postion and time derivatives. One is to either use two fixes which give you each a (x,y,z,t) tuple, while you know what your expected delta-t is, you can calculate the real delta-t and get from that your frequency offset. The other way is to use the doppler shifts of the satelites. You know what position and speed relative to you the satelites have and can from this calculate what your speed, respektive frequency is. 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] ANFSCD - Synchronizing time in home video recorders
One can do many things with a small micro having programmable logic cells, such as the Cypress PSOC. For grins I worked out (via spreadsheet) how to use the PSOC digital divider blocks and the built-in clock PLL to get from 10MHz to 2.048MHz in a fairly precise manner. The scheme uses a divider switched between adjacent moduli (ala the TVB method?) to produce a low frequency that, upon multiplication by the clock PLL, gives an integer multiple of 2.048MHz. Not having actually done it there are 2 questions: 1) Can the 24MHz VCO be pulled to 24.576MHz? and 2) Can the PLL track periodic jitter of about 0.7%. Since there are trimming bits for the VCO I suspect yes to #1, and some sort of passive low pass filter (PI or ladder network?) would reduce the jitter if #2 is a problem. Here's the approach: Feed 10.00 MHz to an 8 bit digital divider block divide by 149 for 237 of 256 times divide by 148 for 19 of 256 times net divide of 148.92578125 to 1 results divide result by 2 in an 8 bit digital divider block (in order to get a good square wave) net divide of 297.85156250 to 1 results at output pin get 33573.77049 Hz, feed over to Ext Osc Input pin PLL of 732x is part of PSOC thus sysclk 24.576000 MHz results and sysclkx2 49.152000 MHz results divide sysclkx2 by 12 in an 8 bit digital divider block divide result by 2 in an 8 bit digital divider block (in order to get a good square wave) Final frequency of 2.048 MHz results to output pin FWIW the result is spot on, at least to the limits of my calculation tools. Bob L. From: Azelio Boriani azelio.bori...@screen.it To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thu, February 2, 2012 12:22:44 PM Subject: Re: [time-nuts] ANFSCD - Synchronizing time in home video recorders Yes, shortly after having sent out the message I realized that I was, as usual, too fast. I'm aware that a simple microprocessor can't be used but a Spartan3 can be involved. Then another problem: the 2.048MHz is about 1/5 of the 10MHz so it is not possible. Sofar the way out is: dividing the 10MHz by 625 and then multiplying by 128 using the DCM in the Spartan3... but nothing clever in this method. Sorry, not a valid contribution. ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
t...@leapsecond.com said: I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. It's the same math as a DDS. If Breseham would land exactly on a grid point after N steps, a DDS will have no long term drift. That means the slope of the Breseham line is N/M where both N and M are integers. For the intermediate steps, both Breseham and DDS come as close as possible: 1/2 grid spacing vs 1/2 clock period. We usually think of DDS as requiring M to be a power of 2 but you don't have to do it that way. One obvious example is to make M a power of 10 by doing decimal adds rather than binary. That should work well with a FPGA but I haven't done it yet. If you start with 10 MHz, that will give you perfect hits on integer audio frequencies. -- 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] FCC Asks If You and GPS Should Be Protected from Interference
Filed my comments. They should be available online in a day or so. Thanks for the word. *** REPLY SEPARATOR *** On 01-Feb-12 at 18:12 John Darwin Powers wrote: Group the following material may be out of context of the normal subject matter, but take notice of the underlined portion in the second paragraph. FCC Asks If You and GPS Should Be Protected from Interference (snippage to save space) Bruce Lane, Owner Head Hardware Heavy, Blue Feather Technologies (http://www.bluefeathertech.com) Assoc. member, AZA AAZK for many moons. Salvadore Dali's computer has surreal ports... ___ time-nuts mailing 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] Fe-5680A -vs- LPRO
Is anyone prepared to comment on the relative performance of the FE-5680A compared with the LPROs? Bruce Hunter, KG6OJI ___ time-nuts mailing 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] GPS SDR (was: FE-.5680A trimming resolution)
I found this homebrew GPS receiver project recently: http://www.holmea.demon.co.uk/GPS/Main.htm No custom specialized chips that are unavailable in small quantities, or which will go obsolete in a few months. I think the best solution for the open source GPS community is to design open source receivers with commodity parts that won't be discontinued in the near future, or for which another commodity part can be substituted if need be. Maybe somebody can extend this design with a 2-bit ADC on the end (not me, too many projects here already...) Dan Schultz N8FGV One of the projects did just this but then the integrated circuit or module that handled the RF and low level functions was discontinued. For a while they scavenged the hardware from other products that used it but then those dried up as well. I believe the best option now would be to find a ubiquitous and well documented receiver that provides low level access but I suspect they no longer exist. ___ time-nuts mailing 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] GPS SDR
Yes, if you need lots o'bits, but a single bit sampler with wide bandwidth is easy (which is why they do it). It's basically a D-latch at the end of the amplifier/limiter chain. Yes, but you lose IIRC about 3dB of performance compared to a 2bit ADC. Only if you get the gain right. A 1-bit ADC does the right thing with any gain. -- 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] 32768 Hz from 10 MHz
Hi Roberto: By changing the timer count dynamically it's possible to lower the jitter to one timer count. See: http://www.prc68.com/I/PClock.shtml#BA Have Fun, Brooke Clarke Hi Brooke, You're a fellow PIC guy; let me explain. Correct, that method works with a modest interrupt rate to count integer seconds without long-term rounding error; but to generate a total of 32,768 as-consistent-as-possible pulses *per* second is quite different. It's possible to use Bresenham with two integers 10,000,000 and 32,768 but I found no way to perform all the 24-bit calculations on an 8-bit PIC quick enough. Removing the GCD often helps but in this case the accumulator remains 3-bytes wide. To generate 32 kHz you have to toggle a pin and calculate if the next toggle must be 38 or 39 instructions in the future; all the math must occur within 37 instructions. That's why I came up with the binary leap year kind of algorithm; it's as close to math-less as you can get. By comparison, all the decimal dividers (1 Hz, 10 Hz, etc.) that you and I do are trivial because of the common factors with the 10 MHz clock. It's just that 32,768 has no factors of 5. Read the comments in the file 10m32k.c for more details. I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the lowest possible jitter? /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] Fe-5680A -vs- LPRO
Is anyone prepared to comment on the relative performance of the FE-5680A compared with the LPROs? Bruce Hunter, KG6OJI I would be interested in such comments too. I judiciously refrained myself from buying an FE-5680A because I own nine LPROs. Antonio I8IOV ___ time-nuts mailing 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] FE5680 missing PPS soln
Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. This logic low is needed to enable one half of the 74AC240 buffer (pin 1) that gates the PPS signal. Don't directly drive LEDs from the LOCK signal on the DB9 and, voila, the PPS signal reappears. Bob -- bob grant bobgr...@fastmail.fm -- http://www.fastmail.fm - Choose from over 50 domains or use your own ___ time-nuts mailing 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] FE5680 missing PPS soln
I did the same thing when I first tested mine. I mounted the regulator and a pair of SMA jacks right to the board it came with using the big board copper as the heat sink for the regulator. I didn't want to build a driver for the LED so I wired it directly (with resistor, of course). Dim and logic low was way up at 2.3 volts. I solved the problem using a high efficiency LED (P/N C503B-RCS-CW0Z0AA1 from Digi-Key). It's running at a bit over half a mA using a 6.2k resistor to the 5 V supply. Now the logic low level is at about 700 mV (still a bit high) and the PPS output works. The LED is bright enough to see from way across the lab. The current generation of LED chemistries is really impressive. -John -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of bob grant Sent: Thursday, February 02, 2012 2:46 PM To: time-nuts@febo.com Subject: [time-nuts] FE5680 missing PPS soln Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. This logic low is needed to enable one half of the 74AC240 buffer (pin 1) that gates the PPS signal. Don't directly drive LEDs from the LOCK signal on the DB9 and, voila, the PPS signal reappears. Bob -- bob grant bobgr...@fastmail.fm -- http://www.fastmail.fm - Choose from over 50 domains or use your own ___ time-nuts mailing 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] GPS receiver vs local oscillator
I thought the 4th satellite was needed to determine the time. Wouldn't it take a 5th satellite to also determine the frequency of the local clock? Not really. There are two ways to get the postion and time derivatives. One is to either use two fixes which give you each a (x,y,z,t) tuple, while you know what your expected delta-t is, you can calculate the real delta-t and get from that your frequency offset. That's the sort of thing I'm looking for, but I don't quite get it yet. I have 4 satellites. If I know f, I can solve for x, y, z, and t. If I don't know f, I'm short an equation. If I get two samples, I have 8 equations and I need to solve for: x0, y0, z0, t0, and f0 x1, y1, z1, t1, and f1 That's 10 unknowns with 8 equations. I get a 9th equation by setting t1 = t0 + 1. I'm still short one equation. Can I do something like assume f0 = f1? That would make sense if the change in frequency is small relative to the noise/error in all the other calculations. The other way is to use the doppler shifts of the satelites. You know what position and speed relative to you the satelites have and can from this calculate what your speed, respektive frequency is. There is a chicken-and-egg problem in there. If I need the local clock frequency to solve for position, I can't use position to solve for frequency. Consider the time-nut case of 1 satellite, known position, and trying to find time. If I know the rough time I can calculate the Doppler. That tells me which FFT bucket to look in. Is the local clock close enough for that even if it's off by a few/10s of PPM? -- 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] 32768 Hz from 10 MHz
On Thu, Feb 2, 2012 at 12:21 PM, Tom Van Baak t...@leapsecond.com wrote: I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the lowest possible jitter? I wonder if your 32K diver could be improved if it used interpolation. In other words use an analog output. So at each cycle you decide what value to put out, either one or zero or some voltage between. The next question is why use a PIC divider? Why not a DDS? For low-end DDS the cost is not much different. Maybe $1 vs. $10 or about that. (don't say 10X say $9 more) The DDS does about the same thing is a PIC except that at each cycle it picks an entry from a sine wave table. I don't know if they interpolate or just use the nearest value. Your algorithm in the PIC, I think is the same as that but you use nearest value in your square wave look up table. Try interpolating. and filtering. This can move to zero crossing to someplace unrelated to the 10MHz reference 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] 32768 Hz from 10 MHz
Now I'm thinking that starting with a first run of 8 cycles at 500nS + 2 cycles at 400nS to be repeated for 10 times and then inserting 2 cycles of 400nS, a first approximation of my 2.048MHz can be done. Maybe with a deltaF/F of 10 at -4 for tau 1 second but it can be done. In the very long run the count will be correct and the accuracy gets better tau after tau. Of course there is the source oscillator's limit. On Thu, Feb 2, 2012 at 9:21 PM, Tom Van Baak t...@leapsecond.com wrote: Hi Roberto: By changing the timer count dynamically it's possible to lower the jitter to one timer count. See: http://www.prc68.com/I/PClock.shtml#BA Have Fun, Brooke Clarke Hi Brooke, You're a fellow PIC guy; let me explain. Correct, that method works with a modest interrupt rate to count integer seconds without long-term rounding error; but to generate a total of 32,768 as-consistent-as-possible pulses *per* second is quite different. It's possible to use Bresenham with two integers 10,000,000 and 32,768 but I found no way to perform all the 24-bit calculations on an 8-bit PIC quick enough. Removing the GCD often helps but in this case the accumulator remains 3-bytes wide. To generate 32 kHz you have to toggle a pin and calculate if the next toggle must be 38 or 39 instructions in the future; all the math must occur within 37 instructions. That's why I came up with the binary leap year kind of algorithm; it's as close to math-less as you can get. By comparison, all the decimal dividers (1 Hz, 10 Hz, etc.) that you and I do are trivial because of the common factors with the 10 MHz clock. It's just that 32,768 has no factors of 5. Read the comments in the file 10m32k.c for more details. I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the lowest possible jitter? /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. ___ time-nuts mailing 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] FE5680 missing PPS soln
I've used an LED direct to the lock output. 330R resistor in series and the other end of the LED to the +5V rail. Works fine for me, but then, I'm not interested in the 1PPS (actually not even sure my bricks have that feature). Rob Kimberley -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of bob grant Sent: 02 February 2012 20:46 To: time-nuts@febo.com Subject: [time-nuts] FE5680 missing PPS soln Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. This logic low is needed to enable one half of the 74AC240 buffer (pin 1) that gates the PPS signal. Don't directly drive LEDs from the LOCK signal on the DB9 and, voila, the PPS signal reappears. Bob -- bob grant bobgr...@fastmail.fm -- http://www.fastmail.fm - Choose from over 50 domains or use your own ___ time-nuts mailing 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] 32768 Hz from 10 MHz
Hi Tom: I like the leap year idea. Does this fit into one of the 8-pin PICs? Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/Brooke4Congress.html Tom Van Baak wrote: Hi Roberto: By changing the timer count dynamically it's possible to lower the jitter to one timer count. See: http://www.prc68.com/I/PClock.shtml#BA Have Fun, Brooke Clarke Hi Brooke, You're a fellow PIC guy; let me explain. Correct, that method works with a modest interrupt rate to count integer seconds without long-term rounding error; but to generate a total of 32,768 as-consistent-as-possible pulses *per* second is quite different. It's possible to use Bresenham with two integers 10,000,000 and 32,768 but I found no way to perform all the 24-bit calculations on an 8-bit PIC quick enough. Removing the GCD often helps but in this case the accumulator remains 3-bytes wide. To generate 32 kHz you have to toggle a pin and calculate if the next toggle must be 38 or 39 instructions in the future; all the math must occur within 37 instructions. That's why I came up with the binary leap year kind of algorithm; it's as close to math-less as you can get. By comparison, all the decimal dividers (1 Hz, 10 Hz, etc.) that you and I do are trivial because of the common factors with the 10 MHz clock. It's just that 32,768 has no factors of 5. Read the comments in the file 10m32k.c for more details. I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the lowest possible jitter? /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. ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
OK for the PSOC example. At the moment I can try on a Spartan3 because I already have a board with the OCXO. The Spartan3 has the so called DCM, a digital clock generator that can multiply an input clock using its DDL digital delay line. On Thu, Feb 2, 2012 at 8:13 PM, Hal Murray hmur...@megapathdsl.net wrote: t...@leapsecond.com said: I'm not sure how well a multi-level leap year algorithm relates Breseham's algorithm. I tracked down his 1965 plotter article. There might be common ground there. It's the same math as a DDS. If Breseham would land exactly on a grid point after N steps, a DDS will have no long term drift. That means the slope of the Breseham line is N/M where both N and M are integers. For the intermediate steps, both Breseham and DDS come as close as possible: 1/2 grid spacing vs 1/2 clock period. We usually think of DDS as requiring M to be a power of 2 but you don't have to do it that way. One obvious example is to make M a power of 10 by doing decimal adds rather than binary. That should work well with a FPGA but I haven't done it yet. If you start with 10 MHz, that will give you perfect hits on integer audio frequencies. -- 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. ___ time-nuts mailing 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] FE5680 missing PPS soln
YMMV but, if there's any chance of a PPS output it'll be arriving at pin 2 of the 74AC240 buffer. -- http://www.fastmail.fm - Accessible with your email software or over the web ___ time-nuts mailing 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] GPS SDR (was: FE-.5680A trimming resolution)
On Thu, 02 Feb 2012 15:05:49 -0500 Daniel Schultz n8...@usa.net wrote: I found this homebrew GPS receiver project recently: http://www.holmea.demon.co.uk/GPS/Main.htm No custom specialized chips that are unavailable in small quantities, or which will go obsolete in a few months. I think the best solution for the open source GPS community is to design open source receivers with commodity parts that won't be discontinued in the near future, or for which another commodity part can be substituted if need be. Maybe somebody can extend this design with a 2-bit ADC on the end (not me, too many projects here already...) This page went over this list a couple of weeks ago. And actually, i marked it as use as reference desgin :-) Also a very interesting design is the one in [1], which is a mostly discrete build GPS/GLONASS receiver. The only integrated components are the PLL, a 10MHz integrated amplifier and a 68k CPU (plus necessary logic, ram, rom around it). Desgning a heterodyne receiver like this (actually super heterodyne as the last mixing stage is in software) is easy. At least today. electronic components working in the GHz range are available for a couple of bucks at single quantities like mixers (eg LT5560, ~3USD), PLLs with integrated VCO's (ADF4350, ~7USD, or LMX2531, ~14USD). Not to mention ADC's with sampling rates as high as 200Msps for just 16USD (ADC08200). All you have to do is find appropriate devices, read the data sheet, apply a fair bit of brain and you get a working design. I know that even a couple of years back, electronic engineers would have killed for these devices that are available to us. Attila Kinali [1] http://lea.hamradio.si/~s53mv/navsats/theory.html -- 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] GPS SDR
On Thu, 02 Feb 2012 12:15:41 -0800 Hal Murray hmur...@megapathdsl.net wrote: Yes, if you need lots o'bits, but a single bit sampler with wide bandwidth is easy (which is why they do it). It's basically a D-latch at the end of the amplifier/limiter chain. Yes, but you lose IIRC about 3dB of performance compared to a 2bit ADC. Only if you get the gain right. A 1-bit ADC does the right thing with any gain. If and only if you get over the minimal gain level :-) Yes, you dont have problems with too much gain. But, then, he problem with too much gain is that you lose ADC resolution, ie in the worst case reducing your fancy 32bit ADC to a simple 1bit ADC/comparator. 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] Building a GPSDO trouble using Jupiter-T
On Thu, Feb 2, 2012 at 6:42 AM, shali...@gmail.com wrote: Magnus, How do they compare in price to the receivers we normally use for timing? Do you see any advantage for a timing receiver to fix faster than once per second? This thread got started when someone asked if an analog PLL would work for building a GSPDO. For that you do need timing pulses much faster then 1PPS. But the analog PLL are not the way to go for best accuracy. -- 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] Fe-5680A -vs- LPRO
Hi They are pretty similar units. They are both within about 7x10^-12 to 1.5x10^11 at one second. Both are within about 1 to 3x10^-12 at 100 seconds. Good samples of both will get much better than that out past 100 seconds. Bad samples of each, not so much. You would have to test a pretty good sized sample to really tell who pulls ahead on short term. Limited data says that the FE is *maybe* a bit better than the LPRO. Both have a temperature coefficient in the 3x10^-10 vicinity over 0 to 70C worst case. Good samples of each do much better. Both units age very little on a daily or weekly basis. You have to watch them for months / years to see real aging. Good samples of each will get down below 1x10^-11 per month. Poor samples do exist. The LPRO has a cleaner RF output spur wise. The power output on the FE's seems to range from +3 to +10 dbm depending on which unit you look at. Power output on the LPRO is a bit better unit to unit. Neither unit is in the rock star category for either phase noise or spurs. The FE runs off of an easier to find supply voltage (+15 rather than +18). The monitor outputs and pps out on the FE are a bit weak. Not a problem if you are driving CMOS logic. The LPRO is better at driving heavier loads. FE's seem to show up without a pps output. I have not seen that issue on LPRO's. Both units pull a major chunk of power at turn on, both get quite hot without a heat sink (or fan) at room. Neither one is suitable for higher temperature operation without some sort of thermal management. FE's right now are in the vicinity of $40 delivered. LPRO's were in this vicinity a couple of years ago if you knew who to get them from. LPRO's are more expensive now. The FE's are going up in price. The LPRO tunes with a voltage and a tuning pot, the FE has a cool serial interface and an eprom. Both units warm up and lock in a similar amount of time. The LPRO lets you look at a voltage to watch the VCXO tune, the FE lets you play with (often undocumented) serial commands see what's going on. The FE interfaces through a DB-9 connector you can get pretty easily. The LPRO uses something a bit less conventional, but still available. Schematic and parts list on both units is a bit of a mystery. There is a bit more on the LPRO simply because people have been reverse engineering them longer. Bottom line, they are very similar devices. The only big deal is the serial interface on the FE vs the tuning on the LPRO. You could easily get a better (or worse) unit buying either part. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of brucekar...@aol.com Sent: Thursday, February 02, 2012 2:48 PM To: time-nuts@febo.com Subject: [time-nuts] Fe-5680A -vs- LPRO Is anyone prepared to comment on the relative performance of the FE-5680A compared with the LPROs? Bruce Hunter, KG6OJI ___ time-nuts mailing 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] FE5680 missing PPS soln
On Thu, 02 Feb 2012 12:46:01 -0800 bob grant bobgr...@fastmail.fm wrote: Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. May i ask what kind of LED you connected and at which current you drove it? I don't know which 74AC240 the FE5680 units use, but Fairchild lists theirs with an absolute maximum rating of +/-50mA. I wouldn't use it to drive more than 20mA, which means that you need at least a current generation LED, or better a high efficiency LED. Such as John Lofgren used. Alternatively, use a small logic level P channel FET like the FDV302P or a small PNP. Attila Kinali [1] For those who don't know, Absolute Maximum Ratings should read as If you exceede these levels, your device will be dead for sure! -- 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] ANFSCD - Synchronizing time in home video recorders
Years ago (in the 80's) I needed to lock a homebrew DDS to an accurate, stable 10 MHz reference (a good TCXO in this case) that was set to WWV/H. Considering that the DDS was clocked at 2^24 Hz (16.777216 MHz) this was slightly awkward, but I did it using standard HC and 4000 logic. The convoluted path was: 10 MHz / 625 = 16 kHz (HC40103 as a div-by-125 and an HC4017 as a div-by-5 would work...) 16 kHz * 32 = 512 kHz (using a 4046 and 4040) 512 kHz /125 = 4096 Hz (using 40103 or similar) From there, it was a no-brainer to compare this with the 16.777216 MHz / 4096 with another 4046/integrator - but the same 'HC4040 that did this also had a tap with 32768 kHz on it. With a fairly slow loop and a low-noise 2^24 Hz VCXO, the DDS's clock was both clean and stable - and tuned in 1 Hz steps! A cheap and more-common 4.194304 MHz crystal would work and I suppose that a similar scheme could be used to lock a 32768 Hz VCXO but I've never tried to 'VCXO a tuning-fork crystal before:-) * * * I, too, have an older (Philips) DVR that has lost its time sync since the analogs went dark. For a while, I used the XDS time code that happened to be in the vertical interval of one of its standard definition DTV PBS station's sub-channels (received on a set-top box and modulated onto a TV channel to which the DVR would look for its time code) but this has code since been dropped. Before I discovered this, I dug up the line 21 (IIRC) code specifications and noted that even a PIC could probably generate the proper code, synchronized either from a GPS or a WWVB receiver. I'd thought about putting it on multiple lines and then RF modulating it for the DVR to see, but lost enthusiasm after I discovered the time code on the sub-channel. Since that went away (about a year ago) I've just remembered to set the clock once a month, not being able to quickly find the specs for the time code again online... 73, Clint KA7OEI ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
No doubt, the correct way to generate accurate clocks from an accurate 10MHz is by PLLs. There are DDS too, then there is a strange method that uses a sort of dual (triple? Quadruple? ...) modulus. The advantage is that you don't need another oscillator (the PLL needs a VCO) or the (co)sine lookup and DAC combination: just divide (oddly, of course, inserting/removing cycles every here and there). Maybe the sigma at short tau isn't so good but in the long run it gets better. The derived clock can be used to synchronize equipment that is not so sensitive at short taus. This method can show how can a clock be not so good in the short term but very good in the long term. On Thu, Feb 2, 2012 at 11:10 PM, Clint Turner tur...@ussc.com wrote: Years ago (in the 80's) I needed to lock a homebrew DDS to an accurate, stable 10 MHz reference (a good TCXO in this case) that was set to WWV/H. Considering that the DDS was clocked at 2^24 Hz (16.777216 MHz) this was slightly awkward, but I did it using standard HC and 4000 logic. The convoluted path was: 10 MHz / 625 = 16 kHz (HC40103 as a div-by-125 and an HC4017 as a div-by-5 would work...) 16 kHz * 32 = 512 kHz (using a 4046 and 4040) 512 kHz /125 = 4096 Hz (using 40103 or similar) From there, it was a no-brainer to compare this with the 16.777216 MHz / 4096 with another 4046/integrator - but the same 'HC4040 that did this also had a tap with 32768 kHz on it. With a fairly slow loop and a low-noise 2^24 Hz VCXO, the DDS's clock was both clean and stable - and tuned in 1 Hz steps! A cheap and more-common 4.194304 MHz crystal would work and I suppose that a similar scheme could be used to lock a 32768 Hz VCXO but I've never tried to 'VCXO a tuning-fork crystal before:-) * * * I, too, have an older (Philips) DVR that has lost its time sync since the analogs went dark. For a while, I used the XDS time code that happened to be in the vertical interval of one of its standard definition DTV PBS station's sub-channels (received on a set-top box and modulated onto a TV channel to which the DVR would look for its time code) but this has code since been dropped. Before I discovered this, I dug up the line 21 (IIRC) code specifications and noted that even a PIC could probably generate the proper code, synchronized either from a GPS or a WWVB receiver. I'd thought about putting it on multiple lines and then RF modulating it for the DVR to see, but lost enthusiasm after I discovered the time code on the sub-channel. Since that went away (about a year ago) I've just remembered to set the clock once a month, not being able to quickly find the specs for the time code again online... 73, Clint KA7OEI ___ time-nuts mailing 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] Building a GPSDO trouble using Jupiter-T
Hence the need for a 100PPS from a Motorola, the 800Hz from a uBlox, the 10KHz from the Jupiter T, the 10MHz from the CW12 (the WI version, recently developed thanks to the time-nuts list). Anyway I still think that an analog GPSDO 1PPS based can be done. Maybe not the best accuracy can be obtained but it can be done. I'm sure Robert Pease would have had something to say about this topic. On Thu, Feb 2, 2012 at 11:06 PM, Chris Albertson albertson.ch...@gmail.comwrote: On Thu, Feb 2, 2012 at 6:42 AM, shali...@gmail.com wrote: Magnus, How do they compare in price to the receivers we normally use for timing? Do you see any advantage for a timing receiver to fix faster than once per second? This thread got started when someone asked if an analog PLL would work for building a GSPDO. For that you do need timing pulses much faster then 1PPS. But the analog PLL are not the way to go for best accuracy. -- 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] FE5680 missing PPS soln
The LEDs are common garden variety, tied to +5V and inline with 1k8...I was expecting 2ma or so. Note, whereas the PPS signal is buffered the LOCK signal for the DB9 is not passed though the 74ACT240 buffer. On Thu, Feb 2, 2012, at 11:10 PM, Attila Kinali wrote: On Thu, 02 Feb 2012 12:46:01 -0800 bob grant bobgr...@fastmail.fm wrote: Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. May i ask what kind of LED you connected and at which current you drove it? I don't know which 74AC240 the FE5680 units use, but Fairchild lists theirs with an absolute maximum rating of +/-50mA. I wouldn't use it to drive more than 20mA, which means that you need at least a current generation LED, or better a high efficiency LED. Such as John Lofgren used. Alternatively, use a small logic level P channel FET like the FDV302P or a small PNP. Attila Kinali [1] For those who don't know, Absolute Maximum Ratings should read as If you exceede these levels, your device will be dead for sure! -- 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. -- http://www.fastmail.fm - The professional email service ___ time-nuts mailing 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] ANFSCD - Synchronizing time in home video recorders
... since the analogs went dark. Are you near any Class-A or low-power stations? Those are still permitted to broadcast NTSC signals. What's in their vertical interval would be a separate question, though. ___ time-nuts mailing 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] Fe-5680A -vs- LPRO -vs- FRS-C
Bob wrote: They [FE-5680A and LPRO] are pretty similar units. [much good stuff snipped.] Another Rb unit that has been available on the surplus market for $50-100 in the past is the FRS-C. How do folks here feel they compare to the FE-5680A and LPRO? 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] ANFSCD - Synchronizing time in home video recorders
OK for the PSOC example. At the moment I can try on a Spartan3 because I already have a board with the OCXO. The Spartan3 has the so called DCM, a digital clock generator that can multiply an input clock using its DDL digital delay line. The original context was keeping wall clock time. In that application, jitter on the 32 KHz clock isn't a problem. If I was hacking with a FPGA, I'd make a decimal addition module and chain 7 of them together and see how fast it goes. The idea is to avoid the DLLs, KISS. If it runs at 10 MHz (100 ns), I'd declare victory and try to see how well it works. I'd probably divide by 32K and compare that with another handy PPS. If it doesn't run at 100 ns, I'd probably insert a pipeline FF in the carry chain, or as many as were needed. It won't change the overall result, just delay the output signal by a clock cycle. If that worked, I might try to see how fast I could get it to run. That's just for fun/ego. The obvious target is 100 MHz which just adds one more decimal counter stage and probably several/many pipeline FFs. That should cut the jitter from 100 ns peak-peak to 10 ns. It won't change the overall frequency stability. -- 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] FE5680 DDS plot
At 03:20 AM 2/2/2012, Javier Herrero wrote: I forgot... have you had the opportunity to check if the difference between the two DDS programming words is the same in all cases? All my readings leds to 1400.00x Hz, I've not looked at it but probably the difference in DDS counts is constant. So far, it's been a constant 1400.001347 Hz. But I've not dialed in a range of offsets yet. According to cmd 0x22, my non-locking unit appears to startup with the DDS at 2.527819 and 18.755189 MHz. (!) -- newell N5TNL ___ time-nuts mailing 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] Building a GPSDO trouble using Jupiter-T
Remarkably, the simplest and still one of the best GPSDO I've tested was the 10 kHz Jupiter and analog PLL-based standard by James Miller. It performed superbly. It's the 4th GPSDO at: http://www.leapsecond.com/pages/gpsdo/ In hindsight, that doesn't seem too surprising. I'm not a Juniper wizard. I could be way off here. I'm assuming the Jupiter does phase jumps every second and uses DDS like mechanisms within each second. The DDS will make spurs. A simple analog filter will get rid of most of them. What gets through will be close in. The phase jumps turn into close in phase noise where close is under 1 Hz. How would you measure that sort of phase noise? -- 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.
[time-nuts] Fe-5680A -vs- LPRO
Bob, WOW! Thanks for the very comprehensive report. Bruce, KG6OJI ___ time-nuts mailing 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] 32768 Hz from 10 MHz
It's possible to use Bresenham with two integers 10,000,000 and 32,768 but I
found no way to perform all the 24-bit calculations on an 8-bit PIC quick
enough. Removing the GCD often helps but in this case the accumulator
remains 3-bytes wide.
To generate 32 kHz you have to toggle a pin and calculate if the next toggle
must be 38 or 39 instructions in the future; all the math must occur within
37 instructions. That's why I came up with the binary leap year kind of
algorithm; it's as close to math-less as you can get.
You missed the simple way. Table lookup. :)
The table is only 256 slots long.
That's toggling between 305 and 306 cycles. If your CPU uses N clocks per
instruction, multiply the table size by N.
In hindsight, I'm embarrassed that I didn't see this much sooner.
10,000,000 is 10^7 or 2^7 * 2^5.
32,768 is 2^15. So we need a factor of 2^8 to get back to where we started.
-
My early introduction to the advantages of table lookup was using Fortran on
an IBM 7094. How do you calculate factorials quickly? The table is only
30-50 slots. Anything bigger generates a floating point overflow.
-
Here is my hack python code that I had to write to see what's going on:
#!/usr/bin/python2
# Given 10 MHz, target is 32 KHz
# What sequence of DDS steps is required?
# How long is the sequence before it repeats.
import sys
Target = 32768
Input = 1000
table = {}
X = 0
K = 0
oldI = 0
for I in range(0,Input):
X += Target
if X = Input:
X -= Input
print %5d %7d %5d %3d % (K, I, X, I-oldI)
if table.has_key(X):
print Found in table:, X
sys.exit(0)
table[X] = K
K += 1
oldI = I
--
These are my opinions, not necessarily my employer's. I hate spam.
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Re: [time-nuts] 32768 Hz from 10 MHz
On Thu, Feb 2, 2012 at 12:21, Tom Van Baak t...@leapsecond.com wrote: It's possible to use Bresenham with two integers 10,000,000 and 32,768 but I found no way to perform all the 24-bit calculations on an 8-bit PIC quick enough. Removing the GCD often helps but in this case the accumulator remains 3-bytes wide. In this particular case, the divisor your want is 2^15 / 10^7. You can remove a common factor of 2^7, giving 2^8 / 5^7, or 256 / 78125. If you only want a square wave output, you should be able to do this with a 17-bit binary counter and some logic. In concept, it looks something like: - initialize register to 0 - every input clock, add 256 to the register - when the register is greater than or equal to 78125, set overflow bit and subtract 78125 from the register. In practice, you'd probably set the register to 78125 and count down to zero, using the borrow output from the subtract of 256 as overflow. Then you don't need to compare the register to 78125. Essentially, you've built a special-purpose DDS whose frequency resolution is 128 Hz , and the output frequency you want is exactly 256*128 Hz. The average frequency is exact, and the output waveform repeats every 1/128 sec. I'm curious how a 10 MHz-driven high-end DDS would generate 32 kHz with the lowest possible jitter? You should be able to use a AD9913 to do the same 256/78125 division described above, with exact output frequency, and sine wave output to boot. If I've understood the datasheet correctly, you would program the main DDS frequency tuning word to 14073748, which gets you as close to 32768 Hz as possible without exceeding it. Using variable modulus mode, you program the FTW and modulus of the secondary DDS to 65276 and 78125. Every input clock, the main FTW of 14073748 is added to the main 32-bit register. At the same time, 65276 is added to the secondary register. If the secondary register exceeds 78125 (which will happen on most clocks with these values), the main register is incremented by 1 and the secondary register has 78125 subtracted. So over the course of 78125 input clocks (1/128 second), the secondary register has 65276*78125 counts total added, which causes it to overflow 65276 times. The main register has 78125*14073748 added to it directly, plus 65276 extra counts from the secondary register overflows. The sum of those two values is exactly 2^40, meaning the main register overflows 2^8 times in 78125 clocks. After 78125 input clocks, both the main and secondary register have returned to zero, so the sequence repeats exactly every 1/128 second. In effect, the secondary register is acting as a variable-modulus DDS that changes the FTW of the primary fixed-modulus DDS by only one count, just often enough to make the division ratio exact. And because the primary DDS is still fixed-modulus, you can still use the top k bits of the accumulator to index into a sine lookup table, and produce a sine wave output. Dave ___ time-nuts mailing 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] GPS SDR (was: FE-.5680A trimming resolution)
On 2/2/12 12:05 PM, Daniel Schultz wrote: I found this homebrew GPS receiver project recently: http://www.holmea.demon.co.uk/GPS/Main.htm No custom specialized chips that are unavailable in small quantities, or which will go obsolete in a few months. I think the best solution for the open source GPS community is to design open source receivers with commodity parts that won't be discontinued in the near future, or for which another commodity part can be substituted if need be. Maybe somebody can extend this design with a 2-bit ADC on the end (not me, too many projects here already...) Dan Schultz N8FGV I still think that finding appropriate off the shelf parts to make a subharmonic sampler would be a better strategy.. It's all about whether you want IF filters and a mixer+LO or RF filters. I think the amps are the same either 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] GPS SDR
On 2/2/12 9:39 AM, Attila Kinali wrote: On Thu, 02 Feb 2012 07:49:53 -0800 Jim Luxjim...@earthlink.net wrote: [ There is a sampling rate around 38-39 MHz that works out nicely for all three bands (actually, any rate in that range probably works..I haven't looked).. It helps that the 3 GPS frequencies are related to a common base. Only if you sample them seperately. Which requires seperate, sharp filters for all of them. Also something that isn't that easy to do. The filters don't have to be all that sharp. What you typically do is a chain of amp/filter/amp/filter/amp/filter, etc, for about 6 stages. I'll ask around about the filters, but I suspect they're a pretty standard ceramic thing (it's a bit high frequency to be a SAW), and since GPS frequencies are standard it's likely to be a catalog part. Also do not forget that Galileo E1 signals have about a 20MHz Bandwidth. The combined E5 frequencies have about 50MHz. I think i've read somewhere that you can get away with 8MHz for the E1 signal. Don't know how the E5 behaves if you limit its bandwith. yes, that might be tricky [Antennas] That's why i said that probably a patch antenna build out of PCBs is the best solution. You can get the copper sheet at 0.1mm precision which would define frequency and polarity properties quite well. The only thing that would have to be done by hand would be the distance from the ground plate. I guestimate that this value is not as critical and that 0.5mm variation should be ok. I've seen dual band patches that were pretty simple. One was air dielectric, so the interplate spacing was set mostly by the spacers. I'd go hunting through patents assigned to Dorne Margolin. (part of EDO, these days, I think). Or even maybe looking at their datasheets. There's also what they call the helibowl antenna which is some form of helix in a bowl shaped reflector/ground plane. googling that might turn up something. From my understanding of antenna theory (which is very little), these are mostly variations on the directivity characteristic (ie to get a more favorable distribution), but do not change much the frequency characteristics. Ie if you don't have the frequency characteristics right with a straight design, there wont be much chance to get them right with a shaped design. True in some designs.. however, in general fat elements have wider bandwidth. Adding oddball protrusions and notches can flatten out a response quite nicely. ___ time-nuts mailing 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] FE5680 missing PPS - hallelujah!
Thank you Bob! I just tried removing the lock indicator LED on my three 5680A units and sure enough, in every case, there was the 1 PPS (+5V, 1 usec, rise/fall time ~100 ns) just as if it had always been there. As a reminder, this and much else useful lore is now collected at the ongoing FE-5680 FAQ at http://www.ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq (and if the answer to any of your nagging FE-5680A questions is missing from the FAQ, please feel free to add it!) -John On 2/2/2012 12:46 PM, bob grant wrote: Some info... Its tempting to attach an LED to the /LOCK signal on the DB9. However this signal is very weak and the LED does not seem very bright and PPS signal does not pulse...Hmm Internally the /LOCK pin is connected the 74AC240 buffer, but with an LED helping to keep the signal voltage high (2.3V) a logic low is never asserted. This logic low is needed to enable one half of the 74AC240 buffer (pin 1) that gates the PPS signal. Don't directly drive LEDs from the LOCK signal on the DB9 and, voila, the PPS signal reappears. Bob ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Lucent RFTGm-II-XO and RFTGm-II-Rb pin outs and interconnect
On 1/29/2012 5:52 PM, J. L. Trantham wrote: I seem to recall seeing this (or perhaps for the 'non-II' units) in the past but can't seem to find it. Can anyone point me to the pin outs and interconnects for these units? Thanks in advance. Joe ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. check Dedier's site ___ time-nuts mailing 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] 32768 Hz from 10 MHz
On Thu, Feb 2, 2012 at 7:16 PM, Hal Murray hmur...@megapathdsl.net wrote:
It's possible to use Bresenham with two integers 10,000,000 and 32,768
but I
found no way to perform all the 24-bit calculations on an 8-bit PIC quick
enough. Removing the GCD often helps but in this case the accumulator
remains 3-bytes wide.
To generate 32 kHz you have to toggle a pin and calculate if the next
toggle
must be 38 or 39 instructions in the future; all the math must occur
within
37 instructions. That's why I came up with the binary leap year kind of
algorithm; it's as close to math-less as you can get.
You missed the simple way. Table lookup. :)
The table is only 256 slots long.
That's toggling between 305 and 306 cycles. If your CPU uses N clocks per
instruction, multiply the table size by N.
Well, I thought table lookup too, but I figured a 2048 x 1 table. Easily
done with a rotating bit and 256 byte table.
Assuming clocking a PIC at 10MHz, you have 2,500,000 instructions per
second. Since there was talk about time to the next toggle, we have
2,500,000/65536 instructions between toggles, ie 38.1470... instructions.
The fraction turns out to be 301/2048, so you have to distribute 301 extra
instructions over every 2048 half-periods of the 32768Hz waveform.
Here's what I would do in a mix of C and asm:
unsigned char bitmask = 0x80;
unsigned char index = 0xFF;
unsigned char table[256] = { // Calculate using a spreadsheet or similar };
bit OutputBit;
asm {
loop:
BCFSTATUS,C
RLFbitmask,F
BTFSS STATUS,C
GOTO IndexOK
RLFbitmask,F ; restore low bit from carry
INCF index,W ; on to the next byte in the table
GOTO DoLookup
IndexOK:
NOP; equalize time in if/else cases
NOP
MOVF index,W
DoLookup:
CALL TableLookup; Not defined here, returns value in W
ANDWF bitmask,W
BTFSS STATUS,Z
GOTO ExtraCycle; 1 cycle if skipped, 2 if executed
ExtraCycle:
}
// Extra delay to get to 38/39 instructions (about 20 instructions if I
counted right)
OutputBit ^= 1; ; Toggle output
goto loop;
This version rotates the mask each time through and increments the index
every 8 times through. You could increment the index each time through and
rotate the mask when the index rolls over. That makes calculating the
table harder though.
No doubt I got the sense of the skips wrong or miscounted instructions
somewhere!
Orin.
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Re: [time-nuts] GPS receiver vs local oscillator
On 3 Feb, 2012, at 05:07 , Hal Murray wrote: I thought the 4th satellite was needed to determine the time. Wouldn't it take a 5th satellite to also determine the frequency of the local clock? Not really. There are two ways to get the postion and time derivatives. One is to either use two fixes which give you each a (x,y,z,t) tuple, while you know what your expected delta-t is, you can calculate the real delta-t and get from that your frequency offset. That's the sort of thing I'm looking for, but I don't quite get it yet. I have 4 satellites. If I know f, I can solve for x, y, z, and t. If I don't know f, I'm short an equation. If you are using an undisciplined free-running oscillator, as most cheap receivers do, you never know f. What you know is the frequency written on the oscillator's package (call it fn, the nominal frequency), but the actual f is a mystery. Whatever f is, however, you assume f=fn and use that oscillator to generate a local timescale to measure signal phases against. When you solve for x, y, z and t from data generated by measuring the phase of the incoming signals against your oscillator, the `t' you compute is actually a delta_t with respect to the local time scale generated from that oscillator. The value of delta_t tells you the phase error of your local timescale, so the rate of change of delta_t from sample to sample tells you the error in the fn you assumed, that is (f/fn) integrated over the sample interval. If I get two samples, I have 8 equations and I need to solve for: x0, y0, z0, t0, and f0 x1, y1, z1, t1, and f1 That's 10 unknowns with 8 equations. I get a 9th equation by setting t1 = t0 + 1. I'm still short one equation. Can I do something like assume f0 = f1? That would make sense if the change in frequency is small relative to the noise/error in all the other calculations. I suspect that if the local oscillator does not exhibit fairly good short term stability there is no hope of any of this working. That doesn't matter, though, since the GPS `t' you compute is actually a delta_t from whatever your local time scale is, so (delta_t1 - delta_t0) directly tells you how the rate of your local time scale differs from the rate of the GPS timescale. The GPS receiver in fact has no knowledge of the GPS `t' other than as a function of the local time scale. The GPS time scale is purely a paper time scale from the receiver's point of view unless the receiver does the additional work of somehow using that information to generate a real timescale out of the paper. Dennis Ferguson ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
