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Re: [Discuss-gnuradio] Question on gr.wavfile_source
From: |
Martin Braun |
Subject: |
Re: [Discuss-gnuradio] Question on gr.wavfile_source |
Date: |
Wed, 24 Jun 2009 09:15:34 +0200 |
User-agent: |
Mutt/1.5.17 (2007-11-01) |
On Tue, Jun 23, 2009 at 04:49:10PM -0700, Brook Lin wrote:
> I'm trying to transmit a wave file using gr.wavfile_source(). To test my
> transmission path, I first transmit a sine wave, and I can receive it and
> sink it to sound card fine. I can hear the sound at the receiver side.
> However, if I change the source using gr.wavfile_source(), I can hear
> nothing at the receiver side but noise. Here is the my tx_path below.
>
> =======================================================
> dac_rate = 128e6
> usrp_interp = 500
> self.u = usrp.sink_c (0, usrp_interp)
> self.u.set_interp_rate(usrp_interp)
> usrp_rate = dac_rate / usrp_interp # 256 kS/s
>
> #src = gr.sig_source_f (32e3, gr.GR_SIN_WAVE, 440, 1) #--I can hear
> it at the receiver side
> src = gr.wavfile_source('test.wav', False) #--nothing can be heard
> at the receiver side
>
> interp_taps = optfir.low_pass (8, # gain
> usrp_rate, # sampling rate
> 8e3, # passband cutoff
> 8e3
> 12e3, # stopband cutoff
> 12e3
> 1.0, # passband ripple
> 60) # stopband
> attenuation
> print 'len(interp_taps)',len(interp_taps)
> self.interpolator = gr.interp_fir_filter_fff (8, interp_taps)
> gain = gr.multiply_const_ff(200)
I can't spot an exact problem, but two things do come to mind:
1) Your gain is awfully low, you're hardly using the dynamic range of
the ADC. Try something like 20000.
2) Use an analog modulation, such as AM (w/ carrier) or FM.
MB
--
Dipl.-Ing. Martin Braun Phone: +49-(0)721-608 3790
Institut fuer Nachrichtentechnik Fax: +49-(0)721-608 6071
Universitaet Karlsruhe (TH) http://www.int.uni-karlsruhe.de/
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