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[Discuss-gnuradio] Re: uses gr.file_sink 32 bit or 64 bit


From: feldmaus
Subject: [Discuss-gnuradio] Re: uses gr.file_sink 32 bit or 64 bit
Date: Fri, 27 Mar 2009 19:52:51 +0000 (UTC)
User-agent: Loom/3.14 (http://gmane.org/)

Johnathan Corgan <jcorgan <at> corganenterprises.com> writes:

> 
> Just to make this completely clear:
Very very thank you Johnathan.

Ok, so i think the gnuradio docu should be updated, because there is
written:
"Data captured directly from the USRP is stored as 32-bit complex, rather than
64-bit complex (gr.sizeof_gr_complex)."

But I+Q is 64 bit complex as you said.

So i have to use the read_complex_binary() function which has
gr.sizeof_gr_complex(64 bit) . So the docu should write:
"Data captured directly from the USRP is stored as 64-bit complex, rather than
32-bit complex."

Further on my graphic does not look like my spectrum in the
FFT-sink.
Therfore should something added, like
how to show this correctly:
c=read_complex_binary('data')
t=100:1:length(c)
f=20*log10(fft(t,c(t)))
plot([real(f), imag(f)])

But this sentences doesn't work correcctly.
I am working on this.

How ever the above has another error???
The <plot> command mixes the real part from I and Q together as
the imag part from I and Q too.
Is this correct ???
Further on the data should go through a fft() and a 20*log()
function ???
My FFT has a size of 1024 is this relevant for the fft() function ?

Regards Markus





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