Hi Except that on the same basis, the non-timing GPS gear is in the $10 to $20 range…
Bob On Sep 9, 2012, at 7:55 PM, b...@lysator.liu.se wrote: > Hi Bob, > > This argument has been done before on time-nuts... sorry for repeating. > > There are geodetic quality GPS reveivers, like the Ashtech Z12-CORS (with > external 5-20MHz input - not the true Z12 Metronome) available for a few > hundred dollars occasionally. I got my Z12 CORS for free, from a site > where it had been replaced by modern GPS/GLONASS receivers. > > I also found three Novatel Millenium OEM3 for ca $100 a piece, which in > their days were used by national time labs. Unfortunately two of them has > developed a problem with a custom IC. > > I am far from having the economic freedom to purchase a new H-Maser or > Cesium. However I still have a HP5065A running in the basement. When new > in the early 1970ties, you could probably have traded the rubidium for the > house it is now running in. > > Conclusion: used geodetic gps equipment are no more expensive, than many > of the oscillators we play with. They might actually once have been used > in the same national time lab... ;-) > > -- > > Björn > > > >> Hi >> >> Indeed true for most non-geodetic gps units. Put another way - true unless >> you have a lot of money. >> >> Bob >> >> On Sep 9, 2012, at 7:25 PM, b...@lysator.liu.se wrote: >> >>> Hi Bob, >>> >>> Probably true for Motorola Oncores. Not very true for geodetic >>> receivers. >>> >>> Until you have a receiver clock that is on par with the satellite clocks >>> AND you are short on visable satellites. This might be true if you can >>> load up a modern cesium in your vehicle, and go for a downtown "urban >>> valley" type of scenario. >>> >>> On a stationary site, your expensive clock will not matter to much, >>> since >>> your solution is already pretty over-determined with some 60 >>> measurements >>> on each epoch. (9 GPS +6 Glonass)*2(L1/L2)*2 (code + phase) >>> >>> -- >>> Björn >>> >>>> Hi >>>> >>>> Position accuracy and timing accuracy are two very different things. >>>> Firmware is optimized to improve either one. "Position" firmware is >>>> often >>>> pretty poor for timing. >>>> >>>> Bob >>>> >>>> On Sep 9, 2012, at 5:05 PM, Chris Albertson <albertson.ch...@gmail.com> >>>> wrote: >>>> >>>>> On Sun, Sep 9, 2012 at 1:14 PM, <b...@lysator.liu.se> wrote: >>>>> >>>>>> True for a cheap oem navigation receiver. Not true for a geodetic >>>>>> quality >>>>>> receiver, who usually have some options (external frequency input, >>>>>> PPS_in) >>>>>> to make them the best timing receivers available. However they are >>>>>> much >>>>>> more expensive than the typical single frequency timing reciver. >>>>> >>>>> I looked at every link and can't see where they give a timing accuracy >>>>> spec on the PPS with respect to UTC. Possition accurracy is very >>>>> good and we might assume the timing is as good. But they don't say it >>>>> is. What's interesting is these GPSes will accept an accurate clock >>>>> input in order to give better location data. That is the opposite of >>>>> a timing GPS where you tell it accurate location data so that it can >>>>> get better timing. Cutting down the unknown in one lets you do >>>>> better in the other. I assume these all cost well over $50. You can >>>>> get a pretty good timing GPS for $30 and it WILL have the PPS error >>>>> specified. >>>>> >>>>> To the OP. None of this matters a lot because PPS is a standard input >>>>> signal. It is easy to swap out a GPS receiver later. Same with the >>>>> OCXO. From a control point of view they are all pretty much the same. >>>>> You can swap them out later >>>>> >>>>> >>>>> Chris Albertson >>>>> Redondo Beach, California >>>>> >>>>> _______________________________________________ >>>>> 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. >> > > > > _______________________________________________ > 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.