With a processor like that, you should be able to clock your dongle at 2 Msps all the time, and then resample. I remember faintly that there was some issue with rtlsdr dongles not working will with lower sampling rates, maybe that's what it is.
On a side note, this allows you to offset-tune and avoid DC spurs, which can be pretty ugly on the RTLSDR. M On 07.08.2015 11:47, Tom Cook wrote: > I'm brand new to SDR and I'm just trying to calibrate my expectations of > what will be possible in real time. I'm hoping someone here can give me > a pointer or two. > > I'm running GNU Radio 3.7.2 on Ubuntu 14.04, having installed from the > Ubuntu repositories. The machine I'm using has an Intel Core i5-2520M > running at 2500MHz. > > I'm constructing flowgraphs in GRC and using an RTL-2832U-based USB > dongle as a receiver. > > I've built a fairly simple broadcast FM stereo receiver as an example. > It has the following components: > * RTL-SDR source (768k sample rate). > * Low pass filter (768k sample rate, 96k cutoff, 4k transition) > * Rational resampler (4x decimation) > * WBFM receiver (quadrature rate 192k) > * Low pass filter (1x decimation, 192k sample rate, 15k cutoff, 2k > transition) > * 2x Band pass filter (1x decimation, 192k sample rate, differing cutoff > and transition) > * Multiply > * Low pass filter (192k sample rate, 15k cutoff, 2k transition) > * Add, subtract > * 2 x rational resampler (4x decimation) > * Audio sink (sample rate 48k) > > My system is not able to run this in realtime, producing regular > underruns (about two per second). Decreasing the receiver sample rate > to 384k and decreasing the decimation factor in the first resampler to 2 > allows it to run in without underruns, from which I deduce that the CPU > is right on the edge of being able to process the flowchart in realtime. > > Are my expectations of what I'll be able to do in realtime unreasonably > high? Is there something I'm missing, that I can do to make this run > much faster? > > Thanks, > Tom > > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > _______________________________________________ Discuss-gnuradio mailing list [email protected] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
