Just curious what would a typical use case for this network be ? My limited understanding of common view GPS in this context is that it can be used for time (and frequency) transfer between labs. Thanks in advance for any replies. Regards Mark Spencer
------------------------------ Message: 6 Date: Tue, 16 Apr 2013 15:53:09 +0200 From: Achim Vollhardt <[email protected]> To: [email protected] Subject: Re: [time-nuts] Common-View GPS Network Message-ID: <[email protected]> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Count me in as well, if you need another participating station. I have my Thunderbolt running 24/7 with a solid stationary antenna.. Achim ------------------------------ Message: 7 Date: Tue, 16 Apr 2013 08:00:39 -0700 From: "WarrenS" <[email protected]> To: "Discussion of precise time and frequency measurement" <[email protected]> Subject: Re: [time-nuts] Common-View GPS Network Message-ID: <E466FE7AD5B9476DB5F8199B1B3CFCBE@Warcon28Gz> Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original "is one better off just taking the simple route and tracking GPS time directly?" My response is Yes, as long as you use the GPS to discipline a good Oscillator. GPS on its own is generally capable of about 10 ns of phase error, pretty much over any time period. So the longer you average the closer you know the frequency. I did some remote common view experiments a while back to see if I could find a way to improvement a GPSDO using low cost dual common view GPS. I used Tbolt GPSs, because they are capable of more than a decade better performance than the 1 ns (with correction) GPS engines (*). For monitoring I used Lady Heather so I could control and get real time data from the remote GPS. After several unsuccessful test using various remote locations, I got smarter and moved the "Remote" GPS under the same roof to see what the limitations where. I found the limitation was in my Antenna. (a 58532A type). That is when I used two antennas, even with everything at the same location, taking common view differences added noise. The only way I was able to improve the noise was to use the same GPS signal thru a splitter going to both GPS. Not real useful for "remote" Common View, so my experiment turned into a dual Tbolt DMTD. For some post I did, see Time Nuts back in Oct of 2011 from "WarrenS" and "ws at Yahoo" "Common View Tbolt-Tic", "DMTD using TBolts" and "Measuring ADEV using TBolt-Tic tester" (*) The TBolt Engine is capable of 1e-11 at 3 seconds. and 1e-12 ADEV at 300 seconds using the difference between two TBolts driven with a common GPS signal, see: <http://www.febo.com/pipermail/time-nuts/attachments/20111023/c84deb5b/attachment-0001.gif> ws ********************* Hello all. Having spent some time working over the last year on GPS time stability measurement, I'm keen to move onwards and upwards and have a go at common-view time transfer. While my receivers are in the post, I have thinking about my next direction. One thought that I have had is to try to write some software that can be used for real-time common-view (public if there is interest, but I am getting ahead of myself I think). My question to those in the know is whether they have found common-view to be useful over medium timescales (say, an hour or four). My understanding is that after a day or so the GPS signal itself becomes usable as a standard, so building a network is probably not tremendously useful over these sorts of time periods, but looking at such as figure 6 of [1], common-view should still be useful between a few minutes and hours. Has anyone here tried using such a method to produce their own short-term time scale, or is one better off just taking the simple route and tracking GPS time directly? Thanks, Lachlan ------------------------------ _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts End of time-nuts Digest, Vol 105, Issue 51 ****************************************** _______________________________________________ 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.
