[Hackrf-dev] Yet another Tutorial (Alexandru Csete)

[john at zaphv.com]

I am decimating in the FIR filter by 5000000/264600.  So I dont know  
if GNURadio automatically round the decimation rate but I have to say  
the audio output sounds perfect.



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> Message: 1

> Date: Sat, 24 Aug 2013 04:53:38 -0500

> From: john at zaphv.com

> Subject: [Hackrf-dev] Yet another Tutorial

> To: hackrf-dev at greatscottgadgets.com

> Message-ID: <20130824045338.15251y4jdne6ri5e at webmail.zaphv.com>

> Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";

> 	format="flowed"

>

> Did a quick write up, very basic stuff that may be usefull to someone

> who is just getting started:

>

> FM Receiver - The Hello World of HackRF and GNURadio

> http://binaryrf.com/viewtopic.php?f=9&t=16

>

> Cheers

>

>

>

> ------------------------------

>

> Message: 2

> Date: Sat, 24 Aug 2013 13:58:00 +0200

> From: Alexandru Csete <oz9aec at gmail.com>

> Subject: Re: [Hackrf-dev] Yet another Tutorial

> To: john at zaphv.com

> Cc: hackrf-dev at greatscottgadgets.com

> Message-ID:

> 	<CAHG=S_fVq9JC+FWMfKJVVX2QFuwrLZKi-frZcrBN-uBtbWbLYw at mail.gmail.com>

> Content-Type: text/plain; charset=ISO-8859-1

>

> Hi John,

>

> Nice tutorial. I noticed that your sample rates do not match.

> Osmocom source: 5 msps.

> Translating FIR filter decimates by 18.

> Output sample rate from FIR: 5e6 / 18 = 277.778 ksps

>

> Consequently, your actual audio rate will be 46.296 kHz and the audio

> sink will be dropping samples. Not sure what the wxgui sink will do.

> It will either drop the extra samples or scale the waterfall

> incorrectly. In any case I recommend that you add a rational resampler

> or a polyphase arbitrary resampler. You could do that right after the

> FIR, but please ensure that you only have rational numbers otherwise

> you will still have mismatch.

>

> For example:

> FIR decimation: 16

> Rational resampler decimation: 3125

> Rational resampler interpolation: 2646

>

> That will give you an output rate of 264.6 ksps and you can leave the

> other blocks unchanged.

>

> Alex

>

>

> On Sat, Aug 24, 2013 at 11:53 AM,  <john at zaphv.com> wrote:

>> Did a quick write up, very basic stuff that may be usefull to someone who is

>> just getting started:

>>

>> FM Receiver - The Hello World of HackRF and GNURadio

>> http://binaryrf.com/viewtopic.php?f=9&t=16

>>

>> Cheers

>>

>> _______________________________________________

>> HackRF-dev mailing list

>> HackRF-dev at greatscottgadgets.com

>> http://nine.pairlist.net/mailman/listinfo/hackrf-dev

>

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> End of HackRF-dev Digest, Vol 7, Issue 23

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