Re: [time-nuts] L1/L2 GPS Receiver
On 18/01/14 04:09, Jim Lux wrote: On 1/17/14 11:35 AM, Magnus Danielson wrote: On 2014-01-16 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? Well, considering that you will need to get the P(Y) signal at 10,23 Mchip/s on both L1 and L2, requiring say 40 Msamples/s for both frequencies, and that you will need to do it for say 12 channeles and a bit of interesting processing beyond doing the same amount of channels for the C/A code, it will be an interesting challenge to do that in CPU code, rather than doing the baseband-processing in some form of hardware/FPGA. ALmost certainly in an FPGA. But unless you want fast acquisition, implementing the tracking loop and despreading in FPGA isn't mindbendingly difficult. I'll bet there's open source out there. Doing it in FPGA isn't all that hard. You build a C/A receiver and then extend it, as you do hand-over from C/A to L1 P(Y) and then lock up on the L2 P(Y). FFT accelerated C/A lockup will benefit also for P(Y) as you get a head-start with C/A and then it is relatively trivial to take the next step. It's this dependence of C/A which makes it OKish from a military standpoint, as the C/A is fairly trivial to jam. You could also record raw bits and decode off line in software in non-real time, as long as your clock that you timestamp with isn't too bad. Indeed. Been there and done that for L1 C/A. If your time-stamps is off, your solution will tell you how of they are. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] L1/L2 GPS Receiver
Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ Michael / K7HIL On Thu, Jan 16, 2014 at 2:04 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: On 16/01/14 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? You want P(Y) capable receivers, which means 20,46 MHz bandwidth on both L1 and L2 bands. You want say 12 channels. Lots of raw sample data to crunch on in real time. I'd say that you would really like to mimic the traditional style of doing the mechanical stuff in HW/FPGA and then do the remainder in some suitable processor. Going from C/A to P(Y) is a bit challangeing on it's own, as you where not supposed to be able to do that, only to get the P code. 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] L1/L2 GPS Receiver
On 1/17/14 8:43 AM, Michael Perrett wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ Is the L2c officially on yet? and how many S/V are radiating it? I know there was some testing last summer for L2c but I don't recall the details. ___ time-nuts mailing 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] L1/L2 GPS Receiver
According to *GPS World*; The U.S. Air Force is directing transmission of continuous CNAV message-populated L2C and L5 signals starting in April 2014. . This is almost always optimistic, I would guess availability within 2014 a very high probability. Michael / K7HIL Ref: http://gpsworld.com/tag/l2c/ On Fri, Jan 17, 2014 at 10:11 AM, Jim Lux jim...@earthlink.net wrote: On 1/17/14 8:43 AM, Michael Perrett wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ Is the L2c officially on yet? and how many S/V are radiating it? I know there was some testing last summer for L2c but I don't recall the details. ___ time-nuts mailing 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] L1/L2 GPS Receiver
On 17 Jan, 2014, at 11:43 , Michael Perrett mkperr...@gmail.com wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ It would be nice to have a receiver for that when they turn it on, but I don't think that's what he wants. The observables used for PPP processing are L1 and L2 carrier phase. You don't need a receiver capable of decoding the P(Y) code but you do need a receiver capable of receiving the full bandwidth of its carrier on both L1 and L2 and tracking the phase. The commercial receivers which do this seem to cost dearly. 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.
Re: [time-nuts] L1/L2 GPS Receiver
On 2014-01-16 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? Well, considering that you will need to get the P(Y) signal at 10,23 Mchip/s on both L1 and L2, requiring say 40 Msamples/s for both frequencies, and that you will need to do it for say 12 channeles and a bit of interesting processing beyond doing the same amount of channels for the C/A code, it will be an interesting challenge to do that in CPU code, rather than doing the baseband-processing in some form of hardware/FPGA. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] L1/L2 GPS Receiver
Michael, On 17/01/14 17:43, Michael Perrett wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ Regardless of how much I love the new civilian signals, they are at best scars at this time, and won't give sufficient improvement just yet. Until then, doing it in processors is possible but interesting. PS. Sorry for the double-post, seems the first email got out but I didn't see it. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] L1/L2 GPS Receiver
On 17/01/14 19:17, Dennis Ferguson wrote: On 17 Jan, 2014, at 11:43 , Michael Perrett mkperr...@gmail.com wrote: Magnus, I believe that he is referencing the the new L2 C/A code, which is not protected. Reference http://www.gps.gov/systems/gps/modernization/civilsignals/ It would be nice to have a receiver for that when they turn it on, but I don't think that's what he wants. The observables used for PPP processing are L1 and L2 carrier phase. You don't need a receiver capable of decoding the P(Y) code but you do need a receiver capable of receiving the full bandwidth of its carrier on both L1 and L2 and tracking the phase. The commercial receivers which do this seem to cost dearly. The receivers out there use the fact that the known P-code is encrypted with a W-code into the Y-code using XOR. Over the years have various degrees of advanced methods provided means to measure L1 C/A-code phase, L1 P(Y) code phase, L1 carrier phase, L2 P(Y) code phase and L2 carrier phase. Some of the earlier receivers only provided a sub-set. Commercial receivers maintain a high price because they see a less price-sensitive market. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] L1/L2 GPS Receiver
On 1/17/14 11:35 AM, Magnus Danielson wrote: On 2014-01-16 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? Well, considering that you will need to get the P(Y) signal at 10,23 Mchip/s on both L1 and L2, requiring say 40 Msamples/s for both frequencies, and that you will need to do it for say 12 channeles and a bit of interesting processing beyond doing the same amount of channels for the C/A code, it will be an interesting challenge to do that in CPU code, rather than doing the baseband-processing in some form of hardware/FPGA. ALmost certainly in an FPGA. But unless you want fast acquisition, implementing the tracking loop and despreading in FPGA isn't mindbendingly difficult. I'll bet there's open source out there. You could also record raw bits and decode off line in software in non-real time, as long as your clock that you timestamp with isn't too bad. ___ time-nuts mailing 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] L1/L2 GPS Receiver
Looking at this graph: http://www.thinksrs.com/assets/instr/PRS10/PRS10diag2LG.gif If you have a good PRS10, it only needs adjusting on the many-hours timescale? How much better is a dual-frequency receiver going to be for this, compared to a single frequency receiver? The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! AW On Thu, Jan 16, 2014 at 6:03 AM, davidh dho...@gmail.com wrote: Folks, I've stumbled across a Novatel 720L, so would like a new receiver module which supports L1/L2. The main goal is to start learning about GPS/Galileo/Beidou. I may use the derived 1pps as input to my PRS10/10811D reference (or may continue using the 58503A). My budget is quite limited. Thanks, david ___ time-nuts mailing 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] L1/L2 GPS Receiver
anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? -- These are my opinions. 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] L1/L2 GPS Receiver
On 16/01/14 20:29, Hal Murray wrote: anders.e.e.wal...@gmail.com said: The real benefit of dual-frequency is you can do post-processing with PPP. Javad has some modules but they start at 3 kUSD - if anyone knows of hobby level priced L1/L2 receivers that can produce rinex-files for PPP processing that would be interesting! Has anybody considered doing it in software? If I wanted to play with that sort of stuff, is there any particular SDR hardware package/project that would good to start with? You want P(Y) capable receivers, which means 20,46 MHz bandwidth on both L1 and L2 bands. You want say 12 channels. Lots of raw sample data to crunch on in real time. I'd say that you would really like to mimic the traditional style of doing the mechanical stuff in HW/FPGA and then do the remainder in some suitable processor. Going from C/A to P(Y) is a bit challangeing on it's own, as you where not supposed to be able to do that, only to get the P code. 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] L1/L2 GPS Receiver
Folks, I've stumbled across a Novatel 720L, so would like a new receiver module which supports L1/L2. The main goal is to start learning about GPS/Galileo/Beidou. I may use the derived 1pps as input to my PRS10/10811D reference (or may continue using the 58503A). My budget is quite limited. Thanks, david ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
