Re: [Discuss-gnuradio] BPSK, Costas loop

[Chuck Swiger]

At 02:13 PM 3/31/2005 -0800, you wrote:

> I am especially interested in using gnuradio for PSK31.


It turns out making a psk31 idle is really simple:

     samp_freq = 48000

        pskmod = 31.25 /2
        bpsk = gr.sig_source_f(samp_freq,gr.GR_COS_WAVE,pskmod,1,0)

        tone = gr.sig_source_f(samp_freq, gr.GR_SIN_WAVE,1e3,1,0)
        mixer = gr.multiply_ff()

        dst = audio.sink(samp_freq)

        self.connect(bpsk,(mixer, 0))
        self.connect(tone,(mixer, 1))
        self.connect(mixer,dst)


here's the above signal: http://webpages.charter.net/cswiger/gnuradio_psk31.jpg
and audio from a 'real' gpsk31: 
http://webpages.charter.net/cswiger/gpsk31_audio.jpg

Not sure if Ilia's block will work for that as we need 'many cycles / bit' 
instead of one
and also pulse shaping. Maybe something like [data source at 31 baud] -> 
[bytes to syms] ->
[interpolation to IF rate with root raised cosine filter] -> [IF mixer] -> 
[usrp].

Anyway, it look real doable, as an elegant solution using the usrp to 
directly translate and
interpolate a signal into the RF domain and do away with the costly 
rube-goldberg audio ssb modulation
mess.

--Chuck