In order to test the changes I've made to the ntpd reference implementation's palisade driver (to add support for newer Resolution boards) I obtained all of the receivers the driver currently supports, along with a Spirent GSS6100 simulator. While looking over the manual for the Thunderbolt I noticed that its adjusted GPS week rollover will happen this year, so I decided to test that first since I didn't see any reports of anyone (successfully) implementing a test for it. I used a Thunderbolt with app 3.00 & core 10.02 that has a rev D DS1620 and 37265 oscillator. The simluator and receiver were warmed up for 2 weeks prior to testing. The simulator was configured with a geostationary orbit so that the receiver estimated error reports could be used without any processing. I set the simulation start time for about 30 minutes before the week 936 rollover to give the receiver some time to tune. Ladyheather was used to monitor the unit with auto-rollover compensation disabled. I was able to observe the rollover with this setup, and the receiver's estimated errors were stable for about 2 hours after the rollover, even though the simulator's OCXO isn't that great. The TB's PPS output was delayed by 12 to 16ns from the simulator's PPS output (after subtracting the TB's estimated error). Two hours after rollover the TB thinks the ephemeris expires and, due to a problem with the simulator, the week number jumps ahead by 7. I had set the navigation message to indicate an ephemeris transmission interval of 24 hours but it seems the Thunderbolt always expects a 2 hour interval even with the fit interval flag set. Once the TB stops using the old ephemeris data it reverts to the almanac orbital parameters (which can't describe a geostationary orbit) and goes into holdover. I verified with a Novatel Superstar that as soon as week 935 ends the simulator incorrectly adds 7 to the week number, but the TB doesn't notice this jump until it thinks the ephemeris has expired. It seems like there is a bug in the simulator firmware where weeks with certain bit patterns don't increment properly. I have the latest firmware, but I don't have a support contract so I can't check with Spirent if this is a known issue. The simulator does not support ephemeris cutovers, or even changing anything in the navigation message in realtime, so I dont know if I can improve this test. Two runs of LH monitoring the unit can be found at https://www.youtube.com/watch?v=FICjkfep7NM https://www.youtube.com/watch?v=DDILnVK6qzA I'll test the week 1024 rollover soon.

> I didn't see any reports of anyone (successfully) implementing a test for it. ... > I obtained all of the receivers the driver currently supports, along with a Spirent GSS6100 simulator. ... Hi Trevor, Matthias Jelen did a test on the Trimble Thunderbolt here: https://www.febo.com/pipermail/time-nuts/2014-September/086664.html https://www.febo.com/pipermail/time-nuts/2015-May/091805.html https://www.febo.com/pipermail/time-nuts/2015-May/091825.html So we're all quite confident that the TBolt 1PPS and 10 MHz will be glitch-free. Mark Sims fixed his LH program so even the date & time will be correct. Still, the more tests the better, and the more thorough the better. Thanks for posting your results. The rest of us are envious that you own or have access to a GPS/GNSS simulator. /tvb

On Sat, 4 Mar 2017 20:39:45 -0800, you wrote: .... >Matthias Jelen did a test on the Trimble Thunderbolt here: > >https://www.febo.com/pipermail/time-nuts/2014-September/086664.html >https://www.febo.com/pipermail/time-nuts/2015-May/091805.html >https://www.febo.com/pipermail/time-nuts/2015-May/091825.html > .... Thanks for the links, I didn't see the 2015 test. Currently the older Spirent simulators are going for very resonable prices on the 'bay. The GSS4100 can be had for under $200 and 6100s frequently pop up for $150. Anything newer is still very expensive, though. It may be necessary to use a multichannel simulator for newer receivers (or multiple synchronized single channel units), as I haven't yet been able to get the Trimble Resolution boards to go into overdetermined mode with a single simulated SV.

Hi > On Mar 5, 2017, at 6:31 AM, Trevor N. <qb4@comcast.net> wrote: > > On Sat, 4 Mar 2017 20:39:45 -0800, you wrote: > .... >> Matthias Jelen did a test on the Trimble Thunderbolt here: >> >> https://www.febo.com/pipermail/time-nuts/2014-September/086664.html >> https://www.febo.com/pipermail/time-nuts/2015-May/091805.html >> https://www.febo.com/pipermail/time-nuts/2015-May/091825.html >> > .... > > Thanks for the links, I didn't see the 2015 test. Currently the older > Spirent simulators are going for very resonable prices on the 'bay. > The GSS4100 can be had for under $200 and 6100s frequently pop up for > $150. One thing a 6100 will let you do is to calibrate the PPS out of your “gizmo” to +/- 5 ns (one sigma). While it’s not an impressive number by TimeNuts standards, it is one of the few ways to get that job done. > Anything newer is still very expensive, though. It may be > necessary to use a multichannel simulator for newer receivers (or > multiple synchronized single channel units), as I haven't yet been > able to get the Trimble Resolution boards to go into overdetermined > mode with a single simulated SV. It would be a bit alarming if you *could* get it to show overdetermined with only a single clock source :) 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.

On Sun, 5 Mar 2017 18:35:25 +0100, you wrote: >One thing a 6100 will let you do is to calibrate the PPS out of your “gizmo” to +/- 5 ns (one sigma). While it’s >not an impressive number by TimeNuts standards, it is one of the few ways to get that job done. I want to eventually characterize the delay of some amplified antennas. It's reported that delay varies significantly over temperature even for geodetic-grade antennas. >> multiple synchronized single channel units), as I haven't yet been >> able to get the Trimble Resolution boards to go into overdetermined >> mode with a single simulated SV. > >It would be a bit alarming if you *could* get it to show overdetermined with only a single clock source :) It's quite odd at face value, but the Thunderbolt will go into "overdetermined" mode with only the 1simulated SV. I just re-checked this with a Resolution-T, and it does go into OD mode with all but 1 SV masked from cold restart using a real SV.