[Hackrf-dev] FSK & PSK

[Dominic Spill]

On 25 November 2015 at 05:54, 김상혁 <tkdgur7896 at gmail.com> wrote:
>
> I am wondering why most of file transfer use FSK (De)Modulation scheme ?

I'm not sure what you mean by "most file transfer", do you have a
particular device/application that you are targeting?  Or are you
trying to build your own system?

> I tried to replace GMSK to QAM or PSK scheme, however it doesn’t work.

Could you provide us with any more informationt han this?  The
flowgraphs?  The way that they fail?

> I couldn’t get any file,but when I saw Rx GUI FFT Sink, I could see signal is sparked at Tx started.

Have you tried to debug this?  I would start by taking out the radio
blocks and writing the samples to file, then reading it back.  This
will make sure that your modulation/demodulation are working as
expected.

After that you will need to look at the FFT (as you are already doing)
and maybe a waterfall plot to see if there is noise that affects your
signal.

You could record the received data to file and view it with inspectrum
to see if it looks as you expect.  Is there noise?  Is the entire
signal present?