On Fri, Oct 05, 2007 at 05:19:38PM -0400, [EMAIL PROTECTED] wrote: > Can anybody tell me why the multi_* versions of the fft and scope > applications (found in the multi-antenna directory) seem to have such a > large gain on the input signal for high decimation values (eg 250), > relative to the non-multi versions (at same -g gain setting) of the fft > and scope aps? I'm saturating the inputs for anything above .3 V p-p > using a function generator, whereas the non-multi versions work fine up to > the 2 V p-p limit of the A/D. > > I'm putting in frequencies of 10 kHz and tuning to 0 Hz. I also noticed > that the magnitudes of the values displayed by the multi_* programs is > dependent on the decimation. At lower decimation values the magnitudes > are much less. This variation is not as pronounced on the non-multi > versions, although there is a 'dip' in the response. To give you some > idea of the magnitude difference: > > for a .3 V p-p 10 kHz sine-wave input, here are the peak values: > > decimation usrp_fft.py (with -S) multi_scope.py > 64 1750 1750 > 128 1750 1750 > 144 1750 2900 > 188 1000 8000 > 200 1200 10000 > 250 1750 25000 > > So for decimations greater than 128 the mult_* applications cannot take 2 > V p-p. Any ideas? > > thanks, > eric
The FPGA rbf's checked into the trunk are probably not up to date for the multi_scope case. I'm not in the habit of building multi-board versions since I'm not sure how to test them. If you've got the free (beer) Quartus tools installed, you can rebuild the rbf's and check. Eric _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
