Re: [Discuss-gnuradio] samples/symbols CPFSK

[Marcus Müller]

Hi Olivier,

as discussed, an FSK with 1 S/symbol is not really much of an FSK; so I can't really confirm that it does what you want (it does do some DPSK, in fact).

When you decimate something by a factor of six, the resampler has to choose a filter that kills the upper 5/6 of the spectrum, inevitably damaging your signal, if your max deviation is more than 1/6 of the nyquist rate. So that's definitely not what you want to do!

As usual, I recommend adding spectrum sinks at practically every point in your flow graph and check whether the signal there looks correct, according to your signal model.

Best regards,

Marcus

On 21.07.2016 21:15, Olivier Goyette wrote:

Hi all !

I've been working on this flowgraph for a while now and I've been able to pinpoint what is not working, but I don't understand how to resolve this so, that's why i'm asking for your guidance.

Take a look at the flowgraph i've joined. The thing that doesn't seem to be working on this setup is the samples/symbol in th CPFSK mod block.

When I set this parameter to 1 i'm able to retrieve my message at the file sink. So it tells me that what I did is okay in some way.

What is not working is when I set the same parameter to 6. At the beginning I wasn't using the rational resampler and it wasn't working. So I thought I would need something to "divide" the number of samples to retrieve each symbols. I tried it with the rational resampler block and set decimation to 6, but then, Daaaaaah......not working again.

There is something I can't work around here because I do not have sufficient knowledge about this samples/symbol thing.

I'd like to hear from you pals if you could give me a bit of information about how to make this work properly.

thank you !

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