Re: [Discuss-gnuradio] Stuck at WBFM Project :

[Cinaed Simson]

On 08/13/2017 09:12 AM, Ash SDR wrote:
> Thanks everyone and sorry , I couldn't reply you all for inputs you gave
> me. I apologies for that... 
> 
>  For Now , I kept aside the WBFM project which I asked questions on  and
> working on the Guided Tutorials from GNU Radio and also tutorials from
> greatScott gadgets video series.
> 
> I have a dumb question about Rational Resampler...    Here is the
> snapshot from tutorials website.. 
> 
> As far as I understand , the Rational resampler  modifies the sampling
> rate of the incoming signal based on Interpolation (or) decimation
> factor....  Is it something like this
> 
> 
> *If my incoming Signal is of 10KHz  with Sampling Rate of 50 KHz  , 
> Rational Resampler (Interpolation : 4 , Decimation : 1)  gives me the
> output as signal of 10KHz and Sample Rate of 50*4 = 200 KHz         ??????*
> 
> Am I Interpreting it correctly... ??????

No.

The sampling rate should be roughly 4 times or greater than the
frequency - to give room for a low pass filter - which it is.

The resampler is used to change the sampling rate when needed.

-- Cinaed


> 
> If thats the case , In the following snapshot ,  Signal of 1KHz of 48KHz
> Sample rate is interpolated by factor 4 ,   Then Output Sampling Rate
> should be 48*4 = 192KHz which is much higher than the Required Nyquist
> rate , But the Frequency sink block shows frequency component at 0.25
> Hz... Is it because of the "samp_rate" variable set in QT GUI Frequency
> Sink..
> 
>  I am also playing around with "samp_rate" block in QT Frequency GUI
> Sink...  If i remove rational resampler and just pass on the signal of
> 1Khz with 48Khz sampling rate   in a QT GUI Frequency sink of
> samp_rate/4 , it outputs the signal as 0.25KHz ///. why so >
> 
> 
> Please let me know If i am interpreting it correctly  as THIS IS VERY
> IMPORTANT FOR ME TO UNDERSTAND.. 
> 
> Thanks
> Ash
> 
> 
> 
> tutorial_two_4.pngresampling_output.png
> 
> On Tue, Aug 8, 2017 at 4:41 PM, Cinaed Simson <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     On 08/07/2017 07:55 PM, Ash SDR wrote:
>     > Hello Everyone ,
>     >
>     > I am a GNU Radio beginner trying to implement Wideband FM Project and
>     > transmit it to my FM receiver at a very lower power.  I am choosing a
>     > frequency in a FM band such that my receiver is not picking anything
>     > from that station/..
>     >
>     > Attached is GRC file which i am working on .and the music file which i
>     > am trying to transmit..
>     >
>     > Can anyone please tell me where I am messing up ?
> 
>     Remove the first rational resampler. Set your audio rate to 48000 Hz,
>     and quadrature rate 192000 Hz.
> 
>     In the second re-sampler set the interpolation to 8000000 Hz and the
>     decimation to 192000 Hz.
> 
>     I'm going to guess you're using the HackRF based on your default values
>     (except for the transmit RF gain which should be 1.)
> 
>     I strongly recommend you spend some time on the going through the
>     tutorials at
> 
>       http://www.greatscottgadgets.com/sdr
>     <http://www.greatscottgadgets.com/sdr>
> 
>     and learn something about your hardware and how to build WBFM receiver
>     befor you try to transmit.
> 
>     -- Cinaed
> 
> 
> 
> 
>     >
>     >
>     > As a beginner , my learning curve is from implemented projects ,
>     > University lectures which are available on-line .. This one is from a
>     > book which i am using to get basic understanding ..
>     >
>     >
>     > Thanks
>     > Ash
>     >
>     >
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