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Re: [Discuss-gnuradio] BPSK, Costas loop
From: |
Chuck Swiger |
Subject: |
Re: [Discuss-gnuradio] BPSK, Costas loop |
Date: |
Fri, 01 Apr 2005 09:43:54 -0500 |
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
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Chuck Swiger <=