Re: [Discuss-gnuradio] grc amplitude demodulation questions

[Tom Rondeau]

On Fri, Feb 4, 2011 at 5:43 PM, Alexandru Csete <address@hidden> wrote:
> On Fri, Feb 4, 2011 at 9:33 PM, <address@hidden> wrote:
>>
>> 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.
>>
>
> The AM demodulator block does not support changing decimation during
> runtime. You can check:
> gnuradio-core/src/python/gnuradio/blks2impl/am_demod.py
> It has no methods for changing any parameters.
>
> However, you can implement your own AM demod (it's very simple) and change
> the decimation of the low pass filter - that should work.
>
> Alex


And feel free to contribute that improvement back, please!

Tom