On Thu, Sep 13, 2007 at 12:53:35PM -0400, [EMAIL PROTECTED] wrote: > Hi all- > > I'm trying to understand the behavior of the USRP/LFRX when used as a low > frequency oscilloscope. I am trying to measure a AM modulated waveform > with carrier frequency 34 kHz, modulated at 4 Hz. The decimation in the > FPGA is 250, with a 10 Hz low-pass fir filter with a decimation factor of
Do you really mean 10 Hz low-pass filter, or is this a typo? > 64 giving an effective sampling rate of 4 kHz, and a high-pass filter at > 50 Hz to remove the 0 Hz (DC) component created by the demodulation. I am > using the std_4rx_0tx.rbf firmware to enable 4 channel reception. > Contrary to my expectations, I can tune to USRP off the 34 kHz and still > pickup the 4 Hz; in fact, it's better if I do tune away from 34 kHz! I > can tune anywhere between 0 and 34.98 and I get a nice waveform. I I tune > to exactly 34 kHz, I get a low frequency modulation at roughly 1.67 Hz on > top of the 4 Hz I'm trying to measure. Here's a snippet of my > (psuedo) code for the first channel: > > usrp --> dinterleaver --> (dinterleaver_ch0)magblock --> lpf --> hpf --> > scope. > > Any thoughts? > > thanks! > eric _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio