Re: [time-nuts] Trimble Thunderbolt no longer determines the correct date
Hmm.. Just a while ago, I watched the heather display on ours go to 12:59:59 and stop... Still giving me 10 MHz though which is all I really need. ___ time-nuts mailing 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] Trimble Thunderbolt no longer determines the correct date
It should only be the failure of producing the wrong "display-date". The internal time system use different gears for everything, so the display-date is a side-product. Adjust with +1024 weeks and you should be all set. Leap-second info work on internal gears. Cheers, Magnus On 07/28/2017 02:36 AM, paul swed wrote: Well quite an unpleasant surprise. So after the 30th do the TBolts stop working or is it a case of just the wrong date? I know my Hp3801s been working just fine and its old. Is the TBolt the same issue. Wrong date but still locks thats all I care about actually. With to respect of some sort of a hack I can see that being fairly difficult. Regards Paul WB8TSL On Thu, Jul 27, 2017 at 8:01 PM, Attila Kinali wrote: On Thu, 27 Jul 2017 17:49:14 -0500 Didier Juges wrote: I cannot imagine a work around since the problem stems from the GPS service only identifying the current date within a particular 1024 weeks epoch unless the government changes the amount of data that is sent over the GPS system. Somebody has to use other method to determine the epoch and add the corresponding offset. There is: There is a 13bit week number in message type 10. This gives a 157 year span instead of the ~19 years of the 10bit week number. This has been part of the GPS standard since IS-GPS-200D which was released in 2004. As such I am a little bit surprised that the u-blox receivers still don't support this message (the LEA-5 family was released in 2007 IIRC). But you can use the UBX RXM-SFRBX messages to get the raw GPS messages and decode them yourself. Attila Kinali -- You know, the very powerful and the very stupid have one thing in common. They don't alters their views to fit the facts, they alter the facts to fit the views, which can be uncomfortable if you happen to be one of the facts that needs altering. -- The Doctor ___ time-nuts mailing 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] Trimble Thunderbolt no longer determines the correct date
Attila, On 07/28/2017 02:01 AM, Attila Kinali wrote: On Thu, 27 Jul 2017 17:49:14 -0500 Didier Juges wrote: I cannot imagine a work around since the problem stems from the GPS service only identifying the current date within a particular 1024 weeks epoch unless the government changes the amount of data that is sent over the GPS system. Somebody has to use other method to determine the epoch and add the corresponding offset. There is: There is a 13bit week number in message type 10. This gives a 157 year span instead of the ~19 years of the 10bit week number. This has been part of the GPS standard since IS-GPS-200D which was released in 2004. As such I am a little bit surprised that the u-blox receivers still don't support this message (the LEA-5 family was released in 2007 IIRC). But you can use the UBX RXM-SFRBX messages to get the raw GPS messages and decode them yourself. Yes, but it is only relevant if you to L2C, on which CNAV is encoded. As far as I have seen, there is no support in the L1 C/A NAV, also known as LNAV, message for anything but 10 bit GPS-week numbers, which brings back the topic. Now, there is a reason I advocate for L2C and L5 capable receivers, this is one of them. Don't blame receiver vendors for not using L2C CNAV messages when they only do L1 C/A receivers. 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] Trimble Thunderbolt no longer determines the correct date
I have updated my version of tboltd to do the following: 1) I incorporated your fix for the GPS epoch rollover, with the following change: Since I was already converting the time internally to the Unix epoch I did not use the Julian conversion, rather I simply modified the returned Unix epoch time prior to writing to the NTP shared memory segment. 2) Sprinkled in some #ifdef statements so the unmodified source will compile on FreeBSD and on Debian Linux. 3) This does not include the gpsdclientd. I may or may not care enough to fix that in the future. Source is available at http://ralphsmith.org/~ralph/tboltd-2017-08-02.tar.gz There are also some changes in there from the 2010 base originally used, mostly parsing of some additional packets. Don't do anything with them though. I also added the ability to write a PID file when running as a daemon on BSD systems. I should probably pull all of this into a github project, and use autoconf or something similar to address cross-platform builds. I'm too lazy to mess with that at the moment. Let me know if this works for you. Ralph AB4RS > Thank you, Ralph! > > Indeed, I had tarred up the branch on github with your original code, > not the branch with my changes...how embarrassing! > > I've updated the tarball and re-arranged the page to make it easier to > find the latest. > > Also, if you make an official version I'll remove my download and just > put back the startup scripts that I have added. Note that I didn't > touch gpsclientd... > > Leigh/WA5ZNU > > On 08/01/2017 09:37 AM, Ralph Smith wrote: >> Thanks for doing this, I was just about to dive into this. I've been >> neck deep in some other things recently and just became aware of this >> issue. >> >> Could you check the source tarball? I just downloaded it and it appears >> to be the unmodified version of my code from 2010. >> >> Ralph >> AB4RS >> >> Sent from my iPhone >> >>> On Aug 1, 2017, at 2:42 AM, Leigh L. Klotz, Jr WA5ZNU >>> wrote: >>> >>> Based on Mark Sims updates to Heather v5.0 I've updated Ralph Smith's >>> NTP daemon to handle the rollover. I haven't updated the gpsd. >>> >>> https://wa5znu.org/2011/08/tbolt/ >>> >>> It's not as ambitious as Mark's update; this one doesn't read system >>> time so it will have to be recompiled again in about 20 years. >>> I took Mark's Julian and Gregorian date calculations as is ;-) >>> >>> This is running now as well as it ever did. Thanks for the great >>> community. >>> >>> Leigh/WA5ZNU >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Thunderbolt - trouble locking with some types of antennas
Hi Jim, On 08/02/2017 03:04 PM, jimlux wrote: On 8/2/17 5:16 AM, Magnus Danielson wrote: BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo. Cool stuff. well, not exactly upgraded - the hardware didn't change - being bolted to the exterior of ISS inside a box inside a box - it was a software change - which is what Software Defined Radios are all about. Yeah, I know, it got a software upgrade. :) Recall when I handed you some clues on how to measure the noise of the input of that receiver. Some time-nuttery truely goes to space. :) 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] Bad Thunderbolt?
Moved to new location and trying to do a location survey using TBolt Monitor. My Symmetricom antenna is in indoor location so only see 2-4 satellites but TBolt monitor generates error messages such as Floating Point Overflow and Address access violations (see attached). Does this imply my Thunderbolt has a problem? Thanks Jerry TBolt_Monitor Error.pdf Description: Adobe PDF document ___ time-nuts mailing 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] Thunderbolt - trouble locking with some types of antennas
On 8/2/17 5:16 AM, Magnus Danielson wrote: BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo. Cool stuff. well, not exactly upgraded - the hardware didn't change - being bolted to the exterior of ISS inside a box inside a box - it was a software change - which is what Software Defined Radios are all about. ___ time-nuts mailing 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] Thunderbolt - trouble locking with some types of antennas
On 08/02/2017 01:20 AM, jimlux wrote: On 8/1/17 12:11 PM, Graham / KE9H wrote: Dider: This is a CDMA signal. (With a 'chip' rate that far exceeds the information rate.) If you put a different correlator on every multipath signal, which are each differently delayed in time, then they can be independently demodulated. (Or time shifted and added back together with some quality indicator for weighting.) So, in CDMA, multipath is used as a form of (time) diversity reception and will improve the signal to noise of the combined signal. By definition, the signal with the least time delay either is, or is closest to, the most direct path. You don't have to necessarily fully demodulate this early signal by itself, just know what its timing is. (And remember where it was, if fading in and out.) Since multi-path is a destructive mechanism in most narrow band radio systems, the above may not be intuitive to people not familiar with CDMA and "rake receiver" based systems. Multipath helps, not hurts, these systems, as long as the multipath delays are most of one chip apart, or more. For GPS raw (off the air), when they post process at JPL, they use a fairly sophisticated correlation process, incorporating an estimator of the underlying time delay trajectory: you can use a later "big peak" to help recover the early "first peak", for instance. Rake receivers (under the name "adaptive equalizers") are also why digital TV works fairly well in high multipath environments - with modern receivers that do this. The real increase in precision comes from the higher sampling rate, i.e. sample per chip, which allows for more elaborate schemes to be used. Narrow correlation, RAKE etc. is all just different approaches to that, but the core comes from the oversampling and increased bandwidth. Just doing increased bandwidth with traditional correlator is know to improve precision as narrow-range multi-path can be better suppressed. Novatel patented an extension to that using a par of narrow correlators to further improve on that aspect. Regardless how you do it, improved bandwidth and related oversampling factor is the enabler, then the weapon of choice to make use of it is the next thing to look at. BTW, I saw that the JPL receiver at ISS got upgraded to support Galileo. Cool stuff. 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] Clocking on
Hi, all, You may find this interesting. « Clocking on » a BBC4 programme on the social and industrial impact of time through the ages at < http://www.bbc.co.uk/programmes/b08rtldq > . "The power of accurate observation is commonly called cynicism by those who have not got it. » George Bernard Shaw ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
