Since Joe is probably eating dinner at the moment… With 55296 point FFT, a 1600 Hz tone (7.5 sa/period) has 55296/7.5=7372.8 cycles in a record - so there is an endpoint discontinuity (i.e. a discontinuity between the first and last points of the record).
A 1500 Hz tone (8 samples per period) has 6912 cycles in a record, so there’s no endpoint discontinuity. I think that what you’re seeing is the result of using a non-windowed FFT. It’s easily addressed, if necessary. Steve > On Jan 9, 2017, at 11:07 PM, Bill Somerville <g4...@classdesign.com> wrote: > > On 09/01/2017 22:28, Bill Somerville wrote: >> ... for sure the three >> magnitudes going into peakup are much flatter when the error is greater ... > Hi Joe, > > Here are some examples, these are DFT magnitudes (s vector) for five > bins around a 1500Hz tone: > > 0.107814305 0.175234795 9.38052759E-02 17124122.0 > 8.95743668E-02 8.78201425E-02 4.62990999E-02 > 7.97733366E-02 0.128112748 0.307582766 17126434.0 > 0.167245105 1.00381924E-02 1.45341307E-02 > 5.32349795E-02 7.02278912E-02 0.130553111 17125166.0 > 0.135780737 6.56466857E-02 0.104219861 > > and here is the same for a 1600Hz tone: > > 79235.5156 191998.594 973516.500 15560843.0 > 432274.188 128688.836 60769.3555 > 79641.3359 192280.516 972233.375 15562208.0 > 432276.500 128727.242 60738.6406 > 79411.3125 192080.391 972825.562 15561087.0 > 431534.812 128623.734 60596.7227 > > These numbers are from print *, s(ipk-2:ipk+2) with DF set to the tone > and FTol at 1000Hz. > > 73 > Bill > G4WJS. > > > ------------------------------------------------------------------------------ > Developer Access Program for Intel Xeon Phi Processors > Access to Intel Xeon Phi processor-based developer platforms. > With one year of Intel Parallel Studio XE. > Training and support from Colfax. > Order your platform today. http://sdm.link/xeonphi > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Developer Access Program for Intel Xeon Phi Processors Access to Intel Xeon Phi processor-based developer platforms. With one year of Intel Parallel Studio XE. Training and support from Colfax. Order your platform today. http://sdm.link/xeonphi _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
