[Hackrf-dev] Yet another Tutorial

[Alexandru Csete]

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

>

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