Re: [Discuss-gnuradio] grc amplitude demodulation questions

[ematlis]

Getting back to my question about adjusting decimation on the fly, and having 
the FFT sink adjust to show the spectrum correctly, I have an example of what I 
am doing on my site at:

www.nd.edu/~ematlis/z.gnuradio

There's a jpg and the grc file there.  If anybody would care to take a look and 
comment, that would be great.  Basically, I want to dynamically adjust the 
software decimation going on in the AM Demod block, and have the result shown 
correctly in the FFT sink.  What I am seeing is the x-axis of the FFT changes, 
but not the position of the spectrum.  A variable slider is used to control the 
decimation value in the AM Demod block, and the Sample Rate in the FFT sink is 
dependent on the same variable, but something is not correct.

Thanks,
eric

--- On Fri, 1/14/11, Josh Blum <address@hidden> wrote:

> From: Josh Blum <address@hidden>
> Subject: Re: [Discuss-gnuradio] grc amplitude demodulation questions
> To: address@hidden
> Date: Friday, January 14, 2011, 2:14 PM
> 
> > I believe the code is already doing this.  Here
> are code segments for
> > 2 fft guis.  The first shows the fft of the raw
> output of the USRP2.
> > This gui responds correctly.  Notice the line:
> > "sample_rate=100e6/usrp2_decim", so I assume that as I
> dynamically
> > adjust usrp2_decim, this value is being updated. 
> However, with the
> > second fft, while there is a similar line:
> > "sample_rate=100e6/usrp2_decim/sw_decim" that includes
> the software
> > decimation value, this fft gui does not correct the
> position of the
> > fft when I dynamically change sw_decim.  The
> x-axis DOES change, but
> > the peaks in the spectrum just stay fixed in their
> relative
> > positions.  Any thoughts?
> > 
> 
> Where else is sw_decim used? Is it used in a parameter that
> can be
> changed at runtime? Look at the generated source code, see
> set_sw_decim
> 
> -Josh
> 
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