Hi - has anything changed in the usrp interface since
what-the-hack ? I just updated to the latest cvs and
suddenly all my radios are broken. Actually they work
but frequencies go haywire in half the band:
My rig sets the src to complex, decim 100, the
ddc to -3.9e6 and mux to 0xf0f0f0f0, and then tunes a
freq-xlating-fir-filter over +- 100khz to get 3.8 to 4.0Mhz.
However things start going crazy over 3916khz. The software
ddc is decimating to a bw of 32khz so that probably explains
why the boundary is 16khz above the usrp ddc.
It was working so well untill I did the update ;)
if PLAY_FROM_USRP:
src = usrp.source_c(0,usrp_decim)
mux = gru.hexint(0xf0f0f0f0)
src.set_pga(0,0)
src.set_mux(mux)
src.set_rx_freq(0,-usrp_center)
tune_offset = -usrp_center - src.rx_freq(0)
rf_LO_L = usrp_center - ( freq - tune_offset ) + 1.8e3
xlate_taps = gr.firdes.low_pass ( \
1.0, rf_sample_rate, 20e3, 10e3, gr.firdes.WIN_HAMMING )
xlate_L = gr.freq_xlating_fir_filter_ccf ( \
fir_decimation, xlate_taps, rf_LO_L, rf_sample_rate )
If usrp_center is 3900e3, xlate_L is ok for freq < 3916e3
but is broken above that, stations at 3957k turn up around 3837 etc.
--Chuck
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