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[Discuss-gnuradio] anything changed in usrp interface?

From: cswiger
Subject: [Discuss-gnuradio] anything changed in usrp interface?
Date: Tue, 9 Aug 2005 21:59:17 -0400 (EDT)

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 ;)

       src = usrp.source_c(0,usrp_decim)
       mux = gru.hexint(0xf0f0f0f0)
       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.


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