I changed the transition band to match the 5M transition band I used on the low pass filter to record the data and things worked.
Paul B. Huter On Nov 23, 2013 10:03 AM, "Tom Rondeau" <t...@trondeau.com> wrote: > On Fri, Nov 22, 2013 at 7:14 PM, Paul B. Huter <paul.b.hu...@gmail.com> > wrote: > > I am trying to view the spectrum from 0-1MHz recorded at 50M. I used a > low > > pass filter to only record 0-30MHz. My frequency translating filter is > > defined as follows: > > > > Decimation: 50 > > Taps: firdes.low_pass(1, samp_rate, 500000, 100) > > Center Frequency: -500000 > > Sample Rate: samp_rate > > > > samp_rate: 50M > > > > Any ideas? > > > > Paul B. Huter > > Let's take a look at what the frequency_xlating filter does: > > http://gnuradio.org/doc/doxygen/classgr_1_1filter_1_1freq__xlating__fir__filter__ccc.html > > It filters a signal at the center frequency you set and then moves > that signal to baseband. You've set a sampling rate of 50 Msps and a > center frequency of -50 kHz. Which means you want to get the signal at > -50 kHz moved to baseband. The output signal will be from -500 kHz to > +500 kHz. > > You should basically be seeing what you would if you set the center > frequency to 0 since you're only moving 50 kHz out of 1 MHz of > spectrum. > > What's the exact problem you're facing, then? > > (Also, once again, you're setting a very tight transition band here > that would cause a gigantic filter.) > > Tom >
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