[Discuss-gnuradio] Fsk demodulation and sync trouble

[samuel verdon]

Hello everybody,

I am building a FSK receiver to recover data on UHF. The bit rate of the data is 9,6kbps sent at 437MHz. I put all the information of the flowgraph.

The data sent are a Stream of 0x55 or in binar « 1010 ». the medium between the emitter and the receiver is coax cable.

Here is my flowgraph on GRC : https://ibb.co/ixMYkn

 

I Use a bladeRF to record the signal. The Spectrum of the reception is the following : https://ibb.co/gA6Nd7

As I can see the signal does not saturate the reception, then the signal should be readable.

 

To summarize my flowgraph :

• Multiply : to center of my signal
• Low pass filter : gross filter to have the signal
• Quadratur demod : demodulate the signal
• Low pass filter (decimation) : keep only the signal and decimate the sample rate for the next block to 10 symbol per sample
• Clock recovery MM : find the clock
• Binary slicer : define 0 and 1

 

At the end of the flowgraph I save the data received in a file and here is the result : https://ibb.co/dJyeQn

I have some holes in my file that I do not understand. I tried to use the polyphase clock sync, I also changed the filter size, Nothing change.

 

Does anyone has an idea where my mistake is ? I am sure that my emitter send the right data. If I miss information, tell me I will provide it/them. I also can send the gnuradio flowgraph.

 

Thank you

 

 

Samv