Hi,

I am trying to build a simple FM transmitter. The signal should be send

by

the USRP to an Spectrum Analyzer. I connected the Daughterboard BasicTX

(TX_A) to a Spectrum Analyzer, but I didn’t see the expected Spectrum.

I used the Frequency Mod Block in grc. I think this Block should

modulate

the signal and the USRP send it out on 12,8 MHz. I hope you can help me

building a graph who do this simple task of frequency modulation. I also

tried the example on this website

http://www.opendigitalradio.org/index.php/Simple_FM_transmitter_using_gnuradio

, but on the spectrum analyzer i also didn’t see the expected values.

from gnuradio import gr

from gnuradio.eng_option import eng_option

from grc_gnuradio import usrp as grc_usrp

from grc_gnuradio import wxgui as grc_wxgui

from optparse import OptionParser

import wx

class top_block(grc_wxgui.top_block_gui):

def **init**(self):

grc_wxgui.top_block_gui.**init**(self, title=“Top Block”)

```
##################################################
# Variables
##################################################
self.samp_rate = samp_rate = 32000
##################################################
# Blocks
##################################################
self.gr_frequency_modulator_fc_0 = gr.frequency_modulator_fc(3)
self.gr_multiply_const_vxx_0 = gr.multiply_const_vcc((100, ))
self.gr_multiply_const_vxx_1 = gr.multiply_const_vff((10, ))
self.gr_sig_source_x_0_0 = gr.sig_source_f(6400, gr.GR_CONST_WAVE,
```

3200,

1, 0)

self.usrp_simple_sink_x_0 = grc_usrp.simple_sink_c(which=0,

side=“A”)

self.usrp_simple_sink_x_0.set_interp_rate(200)

self.usrp_simple_sink_x_0.set_frequency(12800000, verbose=True)

self.usrp_simple_sink_x_0.set_gain(0)

```
##################################################
# Connections
##################################################
self.connect((self.gr_frequency_modulator_fc_0, 0),
```

(self.gr_multiply_const_vxx_0, 0))

self.connect((self.gr_sig_source_x_0_0, 0),

(self.gr_multiply_const_vxx_1,

0))

self.connect((self.gr_multiply_const_vxx_1, 0),

(self.gr_frequency_modulator_fc_0, 0))

self.connect((self.gr_multiply_const_vxx_0, 0),

(self.usrp_simple_sink_x_0, 0))

def set_samp_rate(self, samp_rate):

self.samp_rate = samp_rate

if **name** == ‘**main**’:

parser = OptionParser(option_class=eng_option, usage="%prog:

[options]")

(options, args) = parser.parse_args()

tb = top_block()

tb.Run(True)

–

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