Robert Roberts wrote: > > ----- Original Message ----- > From: Martin Dvh <[EMAIL PROTECTED]> > Date: Monday, April 17, 2006 3:06 pm > Subject: Re: [Discuss-gnuradio] Basic USRP AM Transmission > >>Robert Roberts wrote: >> >>>Hello everyone, >>> >>> >>>I have been experimenting with the Flex400 board and have been >> >>trying to >> >>>implement a basic AM transmitter. I have a WFM and NFM transmitter >>>working, but I cannot get the AM one to transmit correctly. The >> >>code> below generates a much higher frequency tone. Any advice to >>what I am >> >>>doing wrong? Does my output need filtering before connecting to >> >>the> sink? >> >>> >>>self.u = usrp.sink_c () # the USRP sink >>> >>># Code here for setting up the USRP, omitted >>> >>>src = gr.file_source (gr.sizeof_float, "audio-1.dat", True) # >> >>440Hz tone >> >>>file >> >>What is the sample_rate of the audio file >>What is you interpolation rate of the usrp >>What is the duc frequency of your usrp. > > > I have the file source sampled at 32kS/s > > I use the following code for setting up my usrp: > > self.dac_rate = self.u.dac_rate() # 128 MS/s > self.usrp_interp = 400 > self.u.set_interp_rate(self.usrp_interp) > self.usrp_rate = self.dac_rate / self.usrp_interp # 320 kS/s > self.sw_interp = 10 > self.audio_rate = self.usrp_rate / self.sw_interp # 32 kS/s > > # determine the daughterboard subdevice we're using > if options.tx_subdev_spec is None: > options.tx_subdev_spec = usrp.pick_tx_subdevice(self.u) > > m = usrp.determine_tx_mux_value(self.u, options.tx_subdev_spec) > self.u.set_mux(m) > self.subdev = usrp.selected_subdev(self.u, options.tx_subdev_spec) > print "Using TX d'board %s" % (self.subdev.side_and_name(),) > > self.subdev.set_gain(self.subdev.gain_range()[1]) # set max > Tx gain > self.set_freq(options.freq) > self.subdev.set_enable(True) # enable > transmitter > > > This is the same code I used for both a NFM and WFM transmitter, both of > which appeared to transmit without problems. But do you actually put a software interpolator in there somewhere. I didn't see any in your code: >>>self.connect (src, const) >>>self.connect (const, conv) >>>self.connect (conv, gain) >>>self.connect (gain, self.u) should be: self.connect (src, const) self.connect (const, conv) self.connect (conv, gain) self.connect (gain, softwareinterpolator) self.connect(softwareinterpolator,self.u)
greetings, Martin > > Sincerely, > ~Chris~ > >>If the sample rate of your audio file is for example 48000 Herz >>Then the usrp interpolation rate should be 128000000/48000 = 2666 >>Which is I think way out of range for the usrp >>You first have to interpolate in software to something in the range >>of the usrp. >> >>Greetings, >>Martin >> >>>const = gr.add_const_ff (1.0) >>>conv = gr.float_to_complex() >>> >>> >>>gain = gr.multiply_const_cc (4000.0) # transmitter gain >>> >>># connect it all >>> >>>self.connect (src, const) >>>self.connect (const, conv) >>>self.connect (conv, gain) >>>self.connect (gain, self.u) >>> >>> >>> >>> >>>Thanks, >>>~Chris~ >>> >>> >>> >>> >>>_______________________________________________ >>>Discuss-gnuradio mailing list >>>Discuss-gnuradio@gnu.org >>>http://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>> >> >> > _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
