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From: | Christophe Seguinot |
Subject: | Re: Sample Rate & Hardware Considerations Tutorial: GNURadio.org |
Date: | Fri, 1 May 2020 22:53:25 +0200 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 |
Hi James
I've seen some error in your flowgraph which explain that you
were not ble to get a correct sound after demodulation.
How to choose sample rate:
Multiplier in your flowgraph ? in the rational resampler you have
interpolation: int(multiplier*(audio_rate * audio_interp))
QT Waterfall sink:
FM demodulation:
Center Frequency:
Please find attached:
Regards, Christophe
Morning All,I have a question after following the sample rate tutorial and its implementation on the Guided Tutorial Hardware Considerations section on the official site: https://wiki.gnuradio.org/index.php/Guided_Tutorial_Hardware_Considerations
After the first portion of the lesson, one is asked to add new blocks shown below.
- 1x Rational Resampler
- 1x WBFM Receiver
- 1x Audio Sink
- 2x Variable
For the Variable: samp_rate we are told to add the following:
- ID: samp_rate
- Value: 250e3
Now, I know the bandwidth of FM is 250 kHz. What I don't know is why we were asked to make this our sample rate. Coincidence?When I run the example (with a few changes for my hardware, and creating a few more variables) I get a signal stream that seems out of sync.The sound I hear is a constant drop or miss in signal about three times a second. Think waa-waa-waa, each second, in between the radio playing.
I launched SDRSharp to compare output and noticed the sample rate is default at 2.4MI then changed this in my Variable samp_rate and low and behold, the stream is steady.
I have two questions.
- Why was a sample rate of 250K chosen in the example?
- What is the goal of the multiplier?
- In your (Barry Duggan's) example the multiplier helped to remove his static
- In my file, setting this as a variable slider, and adjusting while playing, I see no difference to the sound
Below is my flowgraph, I also attached the .grc file.
Any help is greatly appreciated. Thanks in advance!--
Thanks,
James G HayekYoutube.com/JamesHayek
FMReveiver-02bis.grc
Description: application/gnuradio-grc
TP3_FM_stereo_RX.grc
Description: application/gnuradio-grc
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