Re: [Discuss-gnuradio] hardware->new RF frontend!

[Eric Blossom]

On Mon, Dec 30, 2002 at 12:57:56PM -0800, Saeed Beyty wrote:
> 
> I'm new with GNURadio and hadn't build my own RF frontend yet.
> 
> but i have a new idea about it. We can modulate some voice in PC
> using programms such as MATLAB,the out will be a .WAV file, then
> playing it back and record it on a cassete recorder.

No need to record it to cassete. Just convert the WAV file to native
shorts and use VrFileSource to read it in.  You can use the "sox"
command to convert WAV files to shorts.  Use the -sw option on the
output file to specify signed 16-bit shorts.

Also, you may want to consider trying "octave".  It's pretty close to
a MATLAB clone, but is free software.  Many GNU/Linux distributions
come with it.  If not, you can pick it up at www.octave.org

> but there is a problem about the carrier frequency of modulated
> signal , what must it be , i mean what it the default carrier
> frequency the demos are working with ?

Most of our demos run at 20M samples/second with the IF centered at
5.75MHz.  It's not hard to change.  E.g., in fm_demod1.cc, change the
following line...

const float FM_IF_Freq = 5.75e6;        // output freq of tuner module


Eric