Hi Brian, Bob, Charles, et. al. Bob has a great point about the difference between a one-off in a basement lab, and a commercial product that has to work under any circumstances, wether flying at 50,000 feet at -56C, or in an urban canyon, or under whatever other stress could be thrown at it. In fact the testing and fine tuning does take 90% of a product design cycle. That said here is the ADEV plot from my overnight test with the DOCXO. No comments. This was done without any loop adjustment whatsoever, same board and software that drives the on-board TCXO. I will let the result speak for itself, save to say the loop, the DAC, the DAC reference, and the GPS with a proper OCXO can achieve performance at a level approaching two orders of magnitude better than our spec which is 1ppb for this particular product. PLEASE(!) do not send me emails once you get your board and plug in your own OCXO and don't see similar performance for whatever reasons. There is not much we can do about that, other than say our product meets specifications. On the other hand if you connect a really good OCXO you may even get better performance than I got, but who knows.
Thanks, Said In a message dated 10/20/2014 10:21:15 Pacific Daylight Time, br...@lloyd.aero writes: On Mon, Oct 20, 2014 at 6:48 AM, Bob Camp <kb...@n1k.org> wrote: > Hi > > We tend to focus on this or that enhanced feature in a piece of code. It’ s > fun to talk about. That’s not what keeps most designs from doing what they > should. By focusing on this rather than the testing required, we set people > up to fail. If you start off the project believing you mostly need fancy > code when you mostly need long term testing instead, you hit a wall pretty > fast. Setting up for one is not at all the same as setting up for the other. > Sounds to me like the hardware and code are pretty straight-forward. The difference comes from the terms and coefficients in the PLL loop filter and those need to be optimized for each OCXO. There appear to be here a handful of people who have a pretty good idea of what those coefficients should be for various well-known OCXOs out there. So why not do the GPSD hardware, software, and then provide the coefficients that will get a handful of the more popular OCXOs available out there to within a decade of optimum, certainly closer than what one would be talking about by just bolting x-random OCXO onto an LTE-lite? I suspect there would be a market in the time-nut world for such a critter. -- Brian Lloyd Lloyd Aviation 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.aero +1.210.802-8FLY (1.210.802-8359) _______________________________________________ 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.
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