This is also why most systems like this only allow power of 2 ratios.
Quoting Matt Ettus <[EMAIL PROTECTED]>: > Quoting Chuck Swiger <[EMAIL PROTECTED]>: > > > Hi - Just curious whats the mechanism behind this: using a usrp xmit > > interpolation of 64 we get max signal level, and it drops off a lot if > > changed, say to > > 40 or 80. With interp=64, sample rate of 2000000, sig ampl of 6000, center > > at 14000e3 and freq of 72e3 my output is 3v peak (external amps). > > Change it to interp=80, sample rate of 1600000 it drops way down to .6v > peak > > (-14db). Try 50, 3200000 and get .5v peak out. Even stranger using > interp=60 > > gets 2.7v peak but 68 it's down to .6v. > > > This happens both with the interpolator and decimator. It is due to a > simplification I made to save space in the FPGA. I will be fixing it in the > near future. > > Basically, if you interp/decimate by a power of 2 you get full amplitude > signals. If you use a non-power of 2, you will get lower amplitudes. Using > a > value just greater than a power of 2 will have the worst effect. A value > just > less than a power of 2 should be less noticeable. This is why 68 is so much > lower than 60 in your example above. > > Matt > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
