[Discuss-gnuradio] simple transmit questions

[njm25]

First, I assume that you need 2 seperate computers to run 2 USRP boards (1 to 
transmit and 1 to receive).  I just wanted to make sure.

Second, for a simple transmit using the fm_tx4.py example, how do you change 
the output gain for the transmitting signal.  I assume it has to do with the 
line:

gain = gr.multiply_const_cc (4000.0 / options.nchannels)

but I don't know what the max gain can be set to.

Third, in the fm_tx4.py example, instead of opening a single file of floats and 
doing an FM modulation, I simply want to open 2 seperate files of floats and 
combine them into a single stream of complex data.  I have changed the 
following code as follows but I'm not sure about what I have to change about 
the last line.

class pipeline(gr.hier_block):
    def __init__(self, fg, filename, lo_freq, audio_rate, if_rate):

        src1 = gr.file_source (gr.sizeof_float, "file name and path here", True)
        src2 = gr.file_source (gr.sizeof_float, "file name and path here", True)
        
        # Local oscillator
        lo = gr.sig_source_c (if_rate,        # sample rate
                              gr.GR_SIN_WAVE, # waveform type
                              lo_freq,        #frequency
                              1.0,            # amplitude
                              0)              # DC Offset
        mixer = gr.multiply_cc ()

        converter = gr.float_to_complex()
    
        fg.connect (src1, (converter, 0))
        fg.connect (src2, (converter, 1))
        fg.connect (converter, (mixer, 0))
        fg.connect (lo, (mixer, 1))

        gr.hier_block.__init__(self, fg, src, mixer)


Thanks,
Nick