[Discuss-gnuradio] benchmark_tx/rx with RFX 2400

[Shalabh Jain]

Hello,

I am new to the USRP/gnu-radio world, trying to understand the basic working. I have been trying the following 2 experiments which I've not been able to successfully debug or find documentation for. Can somebody help me out to explain what is going wrong or point to some useful references.

The hardware I am using is the RFX2400 daughterboard with USRP and a 2.4-2.48G antenna. I'm using two separate boards in receive and transmit configuration.

1. I tried the digital/benchmark_tx/rx.py provided with the examples (3.2.2 tarball).  I tried to read from a simple ascii file containing a sequence of numbers repeated 1000 times. I've tried different options modulation schemes but the problems persist. Two main problems in this example

     a) It seems that using the default gmsk modulation, although 179 packets are sent, only 147 are received. Essentially, the last packet is always received in error and the end 15% of the file is always lost.
     b) The transmission seems to be very sensitive to the bit rate specified. i.e. there are several combination of big-rates at which the receiver receives nothing.

2. I tried so send a simple tone across by hooking a sine wave generator to the USRP using the grc. Even that seems the just end up in noise reception. I'm attaching a small snippet of the code generated.

I appreciate any help.

Thanks
Shalabh
 
-------------------------------tx-------------------------------------------
                self.gr_float_to_complex_0 = gr.float_to_complex(1)
                self.gr_sig_source_x_0 = gr.sig_source_f(500000, gr.GR_COS_WAVE, 100000, .5, 0)
                self.gr_sig_source_x_1 = gr.sig_source_f(500000, gr.GR_SIN_WAVE, 100000, .5, 0)
                self.usrp_simple_sink_x_0 = grc_usrp.simple_sink_c(which=0, side="A")
                self.usrp_simple_sink_x_0.set_interp_rate(256)
                self.usrp_simple_sink_x_0.set_frequency(2.44e9, verbose=True)
                self.usrp_simple_sink_x_0.set_gain(80)
                self.usrp_simple_sink_x_0.set_enable(True)

                self.connect((self.gr_float_to_complex_0, 0), (self.usrp_simple_sink_x_0, 0))
                self.connect((self.gr_sig_source_x_0, 0), (self.gr_float_to_complex_0, 0))
                self.connect((self.gr_sig_source_x_1, 0), (self.gr_float_to_complex_0, 1))
------------------------------rx-------------------------------------------
                self.usrp_simple_source_x_0 = grc_usrp.simple_source_c(which=0, side="A", rx_ant="TX/RX")
                self.usrp_simple_source_x_0.set_decim_rate(256)
                self.usrp_simple_source_x_0.set_frequency(2.44e9, verbose=True)
                self.usrp_simple_source_x_0.set_gain(80)
                self.wxgui_fftsink2_2 = fftsink2.fft_sink_c(
                        self.GetWin(),
                        baseband_freq=0,
                        y_per_div=10,
                        y_divs=10,
                        ref_level=50,
                        sample_rate=500000,
                        fft_size=1024,
                        fft_rate=30,
                        average=False,
                        avg_alpha=None,
                        title="FFT Plot",
                        peak_hold=False,
                )
                self.Add(self.wxgui_fftsink2_2.win)
                self.connect((self.usrp_simple_source_x_0, 0), (self.wxgui_fftsink2_2, 0))

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