[Discuss-gnuradio] Help needed to obtain AM Depth of Modulation

[Matt Cooper]

Hi guys!

I am trying to calculate the  Depth of Modulation
<https://en.wikipedia.org/wiki/Amplitude_modulation#Modulation_index>   of
an AM signal using GNU Radio, but I just can't make it work.

To test, I am using a Rode & Schwarz SMB100M signal generator connected to a 
USB SDR receiver <http://www.nooelec.com/store/sdr/nesdr-smart-sdr.html>  .
The connection between them is via cable.

- In the signal generator, I'm using  these settings
<http://i.imgur.com/dYwomJn.jpg>  .
- In GNU Radio, I'm using  this diagram <http://i.imgur.com/YvYZtZ7.png>  .

I know the diagram is wrong (it's illustrative only), but it's exactly here
where I need you help. What I'm trying to achieve is to obtain in GNU Radio
the same depth of modulation as the one set in the signal generator. For
instance, if the generator is set to a depth of 56% (just like in the first
image), I'd like to get that exact(ish) same number in a GNU Radio sink.

As you may have realised at this point, I'm not even near to be an expert in
signal processing and I have not been able to find anything about this
googling around.

Any help will be highly appreciated.
Thanks!



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