Question about Simple Transmitter

hi,

I wrote the code below to transmit a file. although i don’t receive any
error but I don’t see any thing on the spectrum analyzer around 2.4G. it
looks that it doesn’t transmit any thing. can some one tell me what is
the
problem

#!/usr/bin/env python
from gnuradio import gr, gru, modulation_utils
from gnuradio import usrp
from gnuradio import eng_notation
from gnuradio.eng_option import eng_option
from optparse import OptionParser
from gnuradio import blks2impl
from gnuradio import blks2

import random, time, struct, sys

from current dir

from transmit_path import transmit_path
import fusb_options

def build_graph():
payload_bytesize = 1024
mysamples_per_symbol = 3
myexcess_bw = 0.35
mygray_code = True
myverbose= False
mylog= False
txfreq = 2400000000
interpolation = 256
chan = 1
gain = 10
fg = gr.top_block ()
#in this step we need to define the file we want to transmit
Bsrc = gr.file_source (gr.sizeof_char,
“/home/usrp2user/PDF/payload.pdf”, False)

Bframing = gr.simple_framer ( payload_bytesize )

  Bdbpsk = blks2.dbpsk_mod(mysamples_per_symbol, myexcess_bw,

mygray_code, myverbose, mylog)

Busrptx = usrp.sink_c(0)
Busrptx.set_interp_rate(interpolation)
subdev_spec = usrp.pick_tx_subdevice(Busrptx) # choose daughterboard
Busrptx.set_mux(usrp.determine_tx_mux_value(Busrptx, subdev_spec))
subdev = usrp.selected_subdev(Busrptx,subdev_spec) # now we got the
chosen(last line) daughterboard
subdev.set_enable(True) #enabling transmit :just in flex boards
subdev.set_gain(gain)
Busrptx.tune(subdev._which, subdev, txfreq)
#usrp.sink_c.tune(Busrptx, chan, subdev, txfreq)
#usrp.sink_c.set_pga(0,pga_gain_in_db)

fg.connect(Bsrc, (Bframing, 0))
fg.connect(Bframing, Bdbpsk)
fg.connect(Bdbpsk, Busrptx)
return fg

if name == ‘main’:
fg = build_graph ()
fg.run()


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On Fri, Jun 13, 2008 at 07:50:45AM -0700, mehdimolu wrote:

hi,

I wrote the code below to transmit a file. although i don’t receive any
error but I don’t see any thing on the spectrum analyzer around 2.4G. it
looks that it doesn’t transmit any thing. can some one tell me what is the
problem

The output of the dbpsk modulator is on the unit circle.
You need to mulitiple the output by a constant to get it into a
reasonable range for transmission. Try multiplying by 8192 using
gr.multiply_const_cc.

Eric

hi,
I amplified using >>Bamp = gr.multiply_const_cc(8192)<< but still
doesn’t
work.

Regards,
Mehdi

Eric B. wrote:

[email protected]
Discuss-gnuradio Info Page


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