Hi Joe, Sleep is a wonderful thing. I found the problem right away this morning. The first pulse generated by jt65sim (which is a sync pulse) *was* a runt. It was half as long as it should have been — essentially, the wave form was starting promptly at 1.0s into the file, but it was starting half-way through the first pulse. This explains all of the observations that I reported last night. I committed a fix for jt65sim and also a very minor tweak to fchisq65.
There is still a residual 4 millisecond offset caused by the delay inserted by fil6521. I have not yet done anything to remove that because I’m not clear on how it would affect signal subtraction. It’s not at all important for display purposes, as we don’t display enough digits to reveal that small offset (though it is responsible for the perpetual “-“ sign in front of the displayed “0.0” when we process simulated files. Steve k9an > On Nov 25, 2015, at 7:40 PM, Steven Franke <[email protected]> wrote: > > Hi Joe, > OK, now I’m scratching my head. > > I was ready to just put in a half-symbol offset and call it a day, until I > made the mistake of looking into it in more detail… > > 1. the files generated by the windows JTSim program (the ones that we used > for early testing of sfrsd) give DT=0.0 (see the first decode, below) whereas > the files generated by the latest jt65sim are giving the 0.2s offset that you > pointed out. > <dts.tiff> > > 2. I used jt65sim to generate a file with +30dB snr and looked at it with > baudline and also did some plots. No doubt - it does start at 1.0s into the > file. > > But check out the attached pdf which is a plot of the coherently integrated > sync sequence (abs(z) from fchisq65) for the +30dB snr file. The overlayed > plots are from the multiple calls to fchisq65 as the algorithm peaks up f0 > and dt. > > Note that the first (coherently integrated) sync pulse is a runt compared to > the rest. In particular, note that the isolated bits around x-index 275, and > 305 produce sharp peaks, but not the first isolated pulse. I told jt65sim to > generate multiple files, and they all show this phenomenon. > > Does this make any sense to you??? > > Confused, > Steve k9an > <coherent_integration.pdf>------------------------------------------------------------------------------ > Go from Idea to Many App Stores Faster with Intel(R) XDK > Give your users amazing mobile app experiences with Intel(R) XDK. > Use one codebase in this all-in-one HTML5 development environment. > Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. > http://pubads.g.doubleclick.net/gampad/clk?id=254741551&iu=/4140_______________________________________________ > wsjt-devel mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Go from Idea to Many App Stores Faster with Intel(R) XDK Give your users amazing mobile app experiences with Intel(R) XDK. Use one codebase in this all-in-one HTML5 development environment. Design, debug & build mobile apps & 2D/3D high-impact games for multiple OSs. http://pubads.g.doubleclick.net/gampad/clk?id=254741551&iu=/4140 _______________________________________________ wsjt-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/wsjt-devel
