Dan it looks like the thread has re-developed. As my early test of your simple solution demonstrated. Better PPS better stability (Used a TBolt to test this) in the form of semi-short term jitter. The beauty of Dans solution is the user can select the quality and cost of the receiver used. Anything can work. I used the 6M also because of the $11 cost and at the time as a alpha tester there could have been issues. Reality, the 6M was on the shelf. Regards Paul WB8TSL
On Sat, Oct 3, 2015 at 9:47 AM, Bob Camp <[email protected]> wrote: > Hi > > If indeed you are into a professional system, where holdover matters then > a lashup on a bunch of surplus gear likely isn’t going to measure up. Based > on about 10,000 previous posts on the list I’d say that holdover does not > appear > to matter to Time Nuts. It would be difficult to find a thread where > holdover performance > was the main topic. The focus (rightly) seems to be to keep the box locked > to > GPS all the time. That approach (if you can do it) will always give you > the best > timing. > > The “not a T” uBlox units *do* put out “TRAIM" information in the words you > can get at. The data is valid and it can be used if you wish to put the > unit > in holdover. I’m sure it works better with a well known position, but that > it not > a requisite. > > TRAIM was a really big deal back in the mid 90’s. That’s when Motorola put > it on > the Oncore’s and did a lot of publicity on the topic. They saw it as a way > to differentiate > their product in the marketplace. Much of our view of TRAIM is slanted by > the > Motorola information on the topic. > > Here’s one way to look at TRAIM: > > If you are in position hold, you can get timing off of a single satellite. > TRAIM > (just like any estimator) looks at the single input it has and says “that > must be > correct”. Give it two inputs and it can look at the solution for each and > decide if > they are close enough (your TRAIM threshold) to be correct. As you get up > to 8 or > 12 inputs, the right answer may be to throw away the single one that is > (say) a microsecond > off from the rest. Somewhere between 3 satellites and 6 satellites, the “I > need > a solid position” thing becomes less of a factor. > > There are other ways to put the device into holdover. One is to simply > look at the > number of satellites. If you are locked on to less than 4 sats, go into > holdover. It’s not > elegant, but it does work. In the case of a lash up, just translate the “I > have <= 3 sats” info into > “my TRAIM is junk”. Instant holdover. > > Bob > > > > On Oct 2, 2015, at 10:44 PM, Bill Hawkins <[email protected]> wrote: > > > > Actually, the Lucent software uses RAIM, and reports the value in its > > status message. If the position appears to have drifted off, or there > > aren't enough satellites to calculate the position, the software > > declares the oscillators to be free-wheeling, an expression meaning that > > the oscillators are free from discipline and are now drifting. > > > > So yes, the positioning aspects matter. > > > > Disclaimer: I haven't studied RAIM (or TRAIM) enough to know exactly > > what goes on, but that's the behavior I've observed. > > > > Bill Hawkins > > > > > > -----Original Message----- > > From: time-nuts [mailto:[email protected]] On Behalf Of Gregory > > Beat > > Sent: Friday, October 02, 2015 6:07 PM > > To: [email protected] > > Subject: Re: [time-nuts] KS-24361 REF-0 standalone > > > > Dan - > > > > I have been following your experimentation with the surplus Lucent > > KS-24361 REF-0 module, to transform it into a standalone GPSDO. > > > > The original usage of the classic Oncore UT+ GPS receiver for KS-24361 > > REF-1, by Symmetricom / Datum for Lucent, was deliberate. > > For usage at a cellular data/telecom site, the focus was on the timing > > and frequency discipline from the GPS satellite transmission, rather > > than the position or dead reckoning aspects -- used by smartphones, > > automobiles, and other GPS applications on the market. > > === > > A couple of comments. > > While I can appreciate being economical (main criteria) and selecting > > the NEO-6M receiver, I believe that a u-Blox timing specific module > > (like LEA-6T) would be more desirable in this application. > > > > In addition, the u-Blox 6-series is the trailing edge of product support > > (market demand dictates its continuance), while the 7 and 8-series are > > their current modules (largely for the cellular / mobile industry > > (smartphones or cell sites themselves) > > > > u-Blox 6-series Timing Application Note (using the LEA-6T) > > https://www.u-blox.com/sites/default/files/products/documents/Timing_App > > Note_%28GPS.G6-X-11007%29.pdf > > > > IF you successfully adopt the u-Blox module to correctly "mimic" the > > Oncore UT+ GPS receiver command suite, THEN you open up a larger > > audience of "time-nuts" and Frequency Standard users (HP Z3801A > > frequency standard universe) as a receiver alternative. > > http://www.realhamradio.com/GPS_Frequency_Standard.htm > > > > These users may desire a "newer" GPS receiver that has more channels > > (8-channel); latest generation receiver; access to the newest GPS > > constellations. > > TAPR might be interested in sponsoring, as a kit/module, if a wider > > audience existed. > > > > The Heol Designs N024 receiver (France) accomplished this replacement > > role for the Trimble ACE II/III GPS receiver used in the > > Symmetricom/Datum TymServe TS2100. > > Their solution resolved shortcomings in the mid-1990 Trimble receiver > > design and giving this Symmetricom NTP server, time IRIG-B time code > > generator, and 10 MHz reference appliance a new lease on life (no longer > > a door stop). > > http://www.heoldesign.com/index.php?module=products&action=catalog&cat=1 > > 4&id=54 > > > > w9gb > > > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
