On Sep 5, 2013, at 9:05 AM, Tom Van Baak wrote: > Hi John, > > It's not off-topic at all. Thanks for posting. Someday it would be cool if an > amateur precise time project emerged from this effort. > > What is not clear from your link is the accuracy or stability of the LO that > was used. It seems to me, for timing purposes, that one would want to have a > very precise timebase for the binary samples that are collected. > > I suppose it depends if someone just wants to make a homebrew (50 baud) GPS > subcode decoder and navigation receiver, or if someone is interested in > extracting as much precise time from the code and carrier phase as possible. > For our timing niche, SDGPS (Software-Defined GPS) doesn't even need to be > real-time. It's the after-the-fact corrections to the LO that are of interest.
So far I've only looked at this trying to better understand how GPS fundamentally works. But of course I've also wondered if any of these SDGPS projects are a suitable base to experiment with some form of carrier phase tracking for time-nut purposes. Holme's project is interesting in that his front-end is built up from discrete parts rather than using one of the single chip solutions (SE4150, MAX2769). That allows you to use whatever source of better-behaved L1 band LO and reference you might have (e.g. 8662A and doubler). And it would be simple to add some sort of processing of the de-spread signal in the FPGA if this has some advantage over only post-processing. Anyway, lots to think about. _______________________________________________ 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.
