Re: [Discuss-gnuradio] Noise problem in multiband FM transmitter

[Eric Blossom]

On Wed, May 13, 2009 at 11:27:22AM +0530, mayur sarode wrote:
>  Hello,I have built a Multi band NBFMtransmitter.As I increase the number of 
> channels for transmission ,the noise is increasing.How do i counteract this 
> in the code.The code is given below#!/usr/bin/env python## a program to send 
> multiple mp3 playlist on the FM band#in this example a single mp3 is sent 
> over N channels on the fm bandfrom gnuradio import gr, engnotationfrom 
> gnuradio import usrpfrom gnuradio import audiofrom gnuradio import blks2from 
> gnuradio.engoption import engoptionfrom optparse import OptionParserfrom 
> usrpm import usrpdbidimport mathimport sys,os,re,tempfile,time,threadfrom 
> gnuradio.wxgui import stdgui2, fftsink2#from gnuradio import txdebugguiimport 
> wx# instantiate one transmit chain for each callclass 
> pipeline(gr.hierblock2):def init(self, outputfile, lofreq, audiorate, 
> ifrate):gr.hierblock2.init(self, "pipeline",gr.iosignature(0, 0, 0),# Input 
> signaturegr.iosignature(1, 1, gr.sizeofgrcomplex)) # Output signaturesrc = 
> gr.filesource (gr.sizeoffloat,outputfi
>  le, False)fmtx = blks2.nbfmtx (audiorate, ifrate, maxdev=75e3, tau=75e6) # 
> Local oscillatorlo = gr.sigsourcec (ifrate,# sample rategr.GRSINWAVE, # 
> waveform typelofreq,#frequency0.1,# amplitude0)# DC Offsetmixer = 
> gr.multiplycc ()self.connect (src, fmtx, (mixer, 0))self.connect (lo, (mixer, 
> 1))self.connect (mixer, self) ####Working with 
> playlist####################################def 
> mp3toraw(filename,outputfile):print("nice n 19 sox \"%s\" r 32000 t raw f L c 
> 1 %s
> " % (filename,outputfile))os.system("nice n 19 sox \"%s\" r 32000 t raw f L c 
> 1 %s" % (filename,outputfile))# Read in .pls format (can be made e.g., using 
> beepmediaplayer)def readplaylist(fname):input = open(fname, 
> 'r')playlist=[]#[playlist]l = input.readline()# NumberOfEntriesl = 
> input.readline()nentries = 
> int(re.findall("NumberOfEntries=([09]+)",l)[0])print "Number of items in list 
> %d
> " % nentriesi = 1while l:l=input.readline()filepath = 
> re.findall("File[09]+=(.*)$",l)if filepath:print 
> filepath[0]playlist.append(filepath[0])i = i + 
> 1input.close()return(playlist)## just create a standard tempfn (sox will 
> create the file, so remove one made by system)def mktempfn():tf = 
> tempfile.mkstemp(".raw")outputfile = 
> tf[1]os.close(tf[0])os.remove(tf[1])return(outputfile)############################################################################################class
>  wfmtx:def init(self):parser = OptionParser 
> (optionclass=engoption)parser.addoption("T", "txsubdevspec", type="subdev", 
> default=None,help="select USRP Tx side A or B")parser.addoption("f", "freq", 
> type="engfloat", default=90e6, help="set Tx frequency to FREQ (default 
> 90e6)", metavar="FREQ")parser.addoption("l","playlist", action="store", 
> default=None,help="MP3 playlist containing files to 
> air.")parser.addoption("n", "nchannels", type="int", default=4, help="number 
> of Tx channels [1,4]")(options, args) = pars
>  er.parseargs ()if len(args) != 0:parser.printhelp()sys.exit(1)if 
> options.playlist == None:print "No playlist specified
> "sys.exit()# parse playlistplaylist = readplaylist(options.playlist) self.fg 
> = gr.topblock()# setup IQ rate to 320kS/s and audio rate to 32kS/sself.u = 
> usrp.sinkc()self.dacrate = self.u.dacrate()# 128 MS/sself.usrpinterp = 
> 400self.u.setinterprate(self.usrpinterp)self.usrprate = self.dacrate / 
> self.usrpinterp# 320 kS/sself.swinterp = 10self.audiorate = self.usrprate / 
> self.swinterp# 32 kS/s# determine the daughterboard subdevice we're usingif 
> options.txsubdevspec is None:options.txsubdevspec = 
> usrp.picktxsubdevice(self.u)m = usrp.determinetxmuxvalue(self.u, 
> options.txsubdevspec)self.u.setmux(m)self.subdev = 
> usrp.selectedsubdev(self.u, options.txsubdevspec)print "Using TX d'board %s" 
> % 
> (self.subdev.sideandname(),)self.subdev.setgain(self.subdev.gainrange()[1])# 
> set max Tx gainif not self.setfreq(options.freq):freqrange = 
> self.subdev.freqrange()print "Failed to set frequency to %s.Daughterboard 
> supports %s to %s" % 
> (engnotation.numtostr(options.freq),engnotation.numtostr(freqran
>  ge[0]),engnotation.numtostr(freqrange[1]))raise 
> SystemExitself.subdev.setenable(True) # enable transmitterprint "TX freq 
> %1.2f MHz
> " % (options.freq/1e6) sum = gr.addcc ()# Instantiate N NBFM channelsstep = 
> 25e3offset = (0 * step, 1 * step, 1 * step, 2 * step, 2 * step, 3 * step, 3 * 
> step, 4 * step,4 * step )for i in range (options.nchannels):outputfile = 
> mktempfn()# write raw sound to named pipe in 
> thread.startnewthread(mp3toraw,(playlist[i],outputfile))# sleep until we are 
> sure there is something to playtime.sleep(3)print "File size %d
> " % int(os.stat(outputfile)[6]) t = pipeline(outputfile,offset[i], 
> self.audiorate, self.usrprate)self.fg.connect(t,(sum, i))gain = 
> gr.multiplyconstcc (4000.0) # connect it allself.fg.connect (sum, 
> gain,self.u)#src = gr.filesource (gr.sizeoffloat,outputfile, False)# stop and 
> wait to finishprint "Starting to play"self.fg.run()print "Done" #stop and 
> wait to 
> finishself.fg.stop()self.fg.wait()#src=getsrc()#fmtx=getfmtx()#self.fg.disconnect(src,
>  fmtx, gain, self.u)os.remove(outputfile)# hack, we should get pid and kill 
> sox only if necessary.os.system("killall sox")def setfreq(self, 
> targetfreq):"""Set the center frequency we're interested in."""r = 
> self.u.tune(self.subdev.which(), self.subdev, targetfreq)if r:print 
> "r.basebandfreq =", engnotation.numtostr(r.basebandfreq)print "r.dxcfreq=", 
> engnotation.numtostr(r.dxcfreq)print "r.residualfreq =", 
> engnotation.numtostr(r.residualfreq)print "r.inverted=", r.invertedreturn 
> Truereturn Falseif name == 'main':wfmtx()Regards, Mayur Sarode Ge
>  t Yourself a cool, short @in.com Email ID now!

Your message is virtually unreadable.  

Please figure out how to send plain ascii messages that have line
breaks where you want them, not where your mail tool wants them.

Eric