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 2.4M
I then changed this in my Variable samp_rate and low and behold, the stream
is steady.
I have two questions.
1. Why was a sample rate of 250K chosen in the example?
2. 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.
[image: image.png]
Any help is greatly appreciated. Thanks in advance!
--
Thanks,
James G Hayek
Youtube.com/JamesHayek
FMReveiver-02.grc
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