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

 From: Cinaed Simson Subject: Re: [Discuss-gnuradio] Stuck at WBFM Project : Date: Sun, 13 Aug 2017 13:44:44 -0700 User-agent: Mozilla/5.0 (X11; Linux i686; rv:52.0) Gecko/20100101 Thunderbird/52.2.1

```On 08/13/2017 09:22 AM, Andrew Rich wrote:
> I though decimination was throwing away samples
>
> Like decimination of 4 is chuck away every 4 th sample
>
> Dunno what does it mean
>
> Can u up resample ?

Yes, it's called interpolation.

>
> And does it have to be a multiple ?

For the rational resampler, it needs to be a rational ratio of the
interpolation and decimation - which is determined by the flowgraph.

-- Cinaed

>
> A
>
> Sent from my iPhone
>
> On 14 Aug 2017, at 2:12 am, Ash SDR <address@hidden
>
>> 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... ??????
>>
>> 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
>>
>>     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
>>
>>
>>     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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>>     >
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