Simple transmit questions

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

[email protected] wrote:

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.

No, you can have multiple USRPs on one computer. They can be identified
by a unique number programmed into their EEPROMs.

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)

yes

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

The max signal output from the computer to the USRP should be
+32767/-32768. However, the RFX boards will clip somewhere lower than
that.

Matt

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs