Question regarding transmission of a tone using QPSK

[lannan jiang]

Hi all,

    I have been following the PSK guided tutorial https://wiki.gnuradio.org/index.php/Guided_Tutorial_PSK_Demodulation . I am on the mpsk_stage6.grc, but I want to transmit a simple tone instead of a random source, so I added a signal source which generates a sine wave. However, here are my questions:

   1.  I select the output of the signal source as bytes, and the time plot of it is attached. As you can see, the plot looks like bursts. But if I add an audio sink after signal source directly, I hear a constant tone. This does not make sense to me, as I thought I should hear discontinuous sound as the plot shows, could someone explain this?  

    2. With the first question being said,  I am using a constellation modulator (QPSK) that takes 2 bits/symbol.

    How can I feed the output  of signal source ( a 16-bit audio file later on) to the constellation modulator properly?  

Thanks in advance!

Regards,

Lannan Jiang

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