Re: [time-nuts] (UK) NPL open house
I'm hoping to go. should be there until about 6pm. On Wed, May 16, 2018 at 4:53 PM, Dr. David Kirkby < drkir...@kirkbymicrowave.co.uk> wrote: > The visitor guide is now available. > > Even if you are not going, the guide might be of interest. > > http://www.npl.co.uk/upload/pdf/open-house-2018-visitor-guide.pdf > > I've had a reasonable amount of success today phoning NPL and trying to > visit a couple of labs that will not be open, but interest me. No absolute > confirmations yet, as one of the people I wanted to visit is going on jury > service tomorrow, but I'm hopeful one of his colleagues can show me around. > > > Dr David Kirkby Ph.D C.Eng MIET > Kirkby Microwave Ltd > Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, > Essex, CM3 6DT, United Kingdom. > Registered in England and Wales as company number 08914892 > http://www.kirkbymicrowave.co.uk/ > Tel 01621-680100 / +44 1621-680100 > > > On 11 May 2018 at 12:57, Adrian Godwin wrote: > > > Next thursday : > > > > https://www.eventbrite.co.uk/e/national-physical- > > laboratory-open-house-2018-prepare-to-be-amazed-tickets-42330306085 > > ___ > > 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] (UK) NPL open house
The visitor guide is now available. Even if you are not going, the guide might be of interest. http://www.npl.co.uk/upload/pdf/open-house-2018-visitor-guide.pdf I've had a reasonable amount of success today phoning NPL and trying to visit a couple of labs that will not be open, but interest me. No absolute confirmations yet, as one of the people I wanted to visit is going on jury service tomorrow, but I'm hopeful one of his colleagues can show me around. Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD, Essex, CM3 6DT, United Kingdom. Registered in England and Wales as company number 08914892 http://www.kirkbymicrowave.co.uk/ Tel 01621-680100 / +44 1621-680100 On 11 May 2018 at 12:57, Adrian Godwin wrote: > Next thursday : > > https://www.eventbrite.co.uk/e/national-physical- > laboratory-open-house-2018-prepare-to-be-amazed-tickets-42330306085 > ___ > 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] Thunderbolt code phase measurement
I was losing messages for up to 4 seconds on some of the receivers (ResT?) so I commented out that message request. I need to go back and do some tests to see which ones are actually affected. --- > By "hosing" do you mean that you lose messages for the next second? That was a problem with the Resolution T too. ___ 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] Caving In: Throwing Money at Solution
Just dropped orders for 1) Bodnar GPSDO - feed VNA, other lab instruments, and K3s radio2) LeoNTP - time for network and clients.3) SDR-Kits DG8SAQ VNWA 3EC - long list of jobs/projects I really wanted to build a RPi NTP and mod the NORTEL GPSDO for 10Mhz and even maybe build a VNA I have all the materials for the first two projects sitting on the bench. But I looked at the feed line on the floor from the GPS antenna on the 38 ft mast outside, at my projects list, and at my "have to do" list and I simply realized that I can't build everything I want to. not if I want to get my station/lab anywhere near functional in the time I have left! :) So, I've decided to throw money at these three projects. Now I can move on to actually building towers, antennas, and other fun stuff. Trying NOT to feel lazy for NOT building what I can but I have a tiltdown tower and foundation to do, antennas to build, lighting and ground systems to build, etc... For now, I'll just have to accept "good enough" on the GPSDO. Have a great day!Clay, KY5G Sent from my Verizon, Samsung Galaxy smartphone ___ 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 code phase measurement
On May 16, 2018, at 15:01, Mark Sims wrote: > > Many thanks Peter for confirming what I suspected. The problem with the > Trimble receivers is that requesting the satellite C/A code data can hose up > a lot of them. So, I'm stuck with calculating the integer number of > milliseconds. How to do that? I do know my position to a few feet. You can calculate the location of the SV from it's Ephemeris given the time of the set of Observations. Another Oh! Can the TBolt be made to send us Ephemeris data? If so, and if it will also give Code Phase, I'd like a simple way to get that in a compact structure and onto our local LAN from the machine running Heather :) J. > > I have Lady Heather generating RINEX files for the Ublox timing receivers, > the NVS-08, the Furuno GT-87, and the Ashtech Z12 (with both L1/L2 data). It > would be nice to be able to support the Trimble receivers. With L1 only > data I am getting results in the < 200 mm range. The Z12 with L1/L2 data > gets me to around 40 mm. > > > >> If you know your position to within 150 kilometers (0.5 ms), you can > dispense with the pseudorange-assembly arithmetic and just use the code > phase directly, after adding in the appropriate integer number of > milliseconds, only one of which will put you within your known > 300-kilometer-diameter (1 ms) sphere. > ___ > 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 code phase measurement
On May 16, 2018, at 13:58, Peter Monta wrote: > > "Code phase" represents where you are along the 1023-bit C/A code (each bit > or "chip" of this code lasts ~1 microsecond or ~300 meters). The > scaled-by-16 code phase will thus range from 0 to 16*1023. To get the full > pseudorange, though, suitable for placing into a RINEX file for example, you > need to also add in the integer number of code periods from the satellite to > you. ... > If you know your position to within 150 kilometers (0.5 ms), you can dispense > with the pseudorange-assembly arithmetic To put that in code, the assembly of collected Observations might look like this: raw_time = nav_ms_of_frame(sv); raw_time += ((double)(1023< and just use the code phase directly, after adding in the appropriate integer > number of milliseconds, only one of which will put you within your known > 300-kilometer-diameter (1 ms) sphere. Oh... that is a very useful simplification when in Over Determined Clock. So long as your time is already accurate to better than 0.5ms, which is no big trick. Seems obvious now, but I hadn't thought of calculating or validating psudoranges that way before, thanks! J. > Cheers, > Peter > ___ > 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] uBlox NEO-M8T lesson: let it run
I have the NEO-M8T-0-01, which doesn't have Galileo, but I'm running with GPS and GLONASS enabled. (I was shipped old stock by a supplier. I'd love to upgrade the firmware to 3.01 TIM 1.10 to be able to get the Galileo constellation, but I'm just an individual. All my emails offering to sign an NDA to get it have not been replied to.) My antenna is a Tallysman TW4722 Wideband GNSS Dual Feed pre-filtered. I'm constrained to less than half of a full sky view (at Lat 45, from near ground level, a width of around 175 degrees of azimuth, aimed 30 degrees East of South) with multipath from infrastructure and mostly low buildings. I've been improving results by using signal level threshold, minimum elevation threshold and RF absorbing material for shields, to try to filter out SVs without line-of-sight to the antenna. I even got improvements by putting the GNSS module inside an insulated thick-walled aluminum can for thermal stability, possibly some RF benefit. All was of benefit, but with that limited skyview I was getting a low SV count and a number of short periods each day where I'd be thrown into holdover due to zero SVs. Adding in Galileo would be really useful to have more SVs in that skyview. Recently, after reviewing the gain map of patch antennas, I decided to see if I could make better use of the area of maximum gain by pointing its vertical axis more at the centre of my sky view, for higher signal strength, but at risk of more multipath off the ground. So I tilted its circular ground plane 30 degrees at my sky view. Immediately I saw higher signal levels and more SVs above the signal level threshold (18 dB). So I decided to write some code to disable SVs that couldn't have line-of-sight to my antenna, based on an azimuth range. To that end, I starting going through the M8 message codes. I didn't find a way to manually exclude an SV, but I discovered UBX-CFG-NMEA - "Consider" QUOTE u-blox receivers use a sophisticated signal quality detection scheme, in order to produce the best possible position output. This algorithm considers all SV measurements, and may eventually decide to only use a subset thereof, if it improves the overall position accuracy. If Consideration mode is enabled, all satellites, which were considered for navigation, are communicated as being used for the position determination. If Consideration Mode is disabled, only those satellites which after the consideration step remained in the position output are marked as being used. UNQUOTE With the ublox u-center, I found that Consider was Enabled. With Consider Disabled, the list of SVs indicated those actually used in the solution. Encouraged by the initial results, I dialed back the signal level threshold to 16 dB (from 18). I then observed, with Lady Heather providing the SV list and the sky map: 1. Every SV that doesn't have line-of-sight to my antenna is excluded from the solution. - The M8T solution is excluding SVs showing as visible that are only visible to the antenna by reflecting from buildings, structural steel posts, or an electrical transformer on pole. 2. A regular number of short incidents where a SV, although positioned within my sky view, is excluded from the solution. Turns out this matches when the SV's line-of-sight signal path is either blocked by or runs close to: - some steel posts, - an entrance roof, - an electrical transformer on pole, - some hydro wires running parallel to my building, or - the horizon or buildings on the horizon (but only at some azimuths). 3. The count of satellites went from: - before: typically two, three or four available to consider for a solution, to - now: typically five or six used for the solution. 4. Astoundingly fewer holdover periods per day: - One short period with zero SVs. - A second short period with a count of two SVs. I may have to lower or remove the signal level threshold, as any solution should be better than going into holdover? With the Consider disabled, I get to see that the M8T is only using valid satellites for its solution - the same ones I would have manually chosen (less a few more when in a position with somewhat dynamic issues I wouldn't have been able to easily detect or even detect, let alone address) - and I got to dial back threshold. No more point in trying to find a way to code excluding SVs. Except for being able to get the updated firmware to add the Galileo constellation in so I'm without holdovers, I'm done. Just let the M8T run and do its job. Now I finally feel the M8T was money well spent. Michael ___ 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 code phase measurement
Hello Mark By "hosing" do you mean that you lose messages for the next second? That was a problem with the Resolution T too. I wanted to get ephemerides from the receiver so I ended up minimising lost messages by tracking satellites as they popped into view, and then requesting an ephemeris after a suitable wait. This problem went away in the SMT 360. Regard resolving the ms ambiguity, you could look at the code in mktimetx, which does just what Magnus D describes. The code lives at https://github.com/openttp/openttp/tree/master/software/gpscv/common/process/ Cheers Michael On Wed, 16 May 2018 at 4:02 pm, Mark Sims wrote: > Many thanks Peter for confirming what I suspected. The problem with the > Trimble receivers is that requesting the satellite C/A code data can hose > up a lot of them. So, I'm stuck with calculating the integer number of > milliseconds. How to do that? I do know my position to a few feet. > > I have Lady Heather generating RINEX files for the Ublox timing receivers, > the NVS-08, the Furuno GT-87, and the Ashtech Z12 (with both L1/L2 data). > It would be nice to be able to support the Trimble receivers. With L1 > only data I am getting results in the < 200 mm range. The Z12 with L1/L2 > data gets me to around 40 mm. > > > > > If you know your position to within 150 kilometers (0.5 ms), you can > dispense with the pseudorange-assembly arithmetic and just use the code > phase directly, after adding in the appropriate integer number of > milliseconds, only one of which will put you within your known > 300-kilometer-diameter (1 ms) sphere. > ___ > 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.
