I'm trying to demodulate a radio signal from Motorol DP4801 (MOTOTRBO) that follows DMR specification.

I'm receiving the signal by using HackRF with the rate sample 1 MHz. The radio uses frequency 406MHz. According to the standard DMR uses 4FSK modulation with the following deviations:

Symbol +3 - +1,944 kHz

Symbol +1 - +0,648 kHz

Symbol -1 - -0,648 kHz

Symbol -3 - -1,944 kHz

The RF carrier bandwidth is 12,5 kHz.

Because after the sampling the radio signal I've lost the original signal (406 MHz) I can't understand how I should set up bandpass filters to catch these deviations. I need it because I'm going to apply non-coherent FSK demodulation but as in the image but for 4 symbols.

enter image description here

  • $\begingroup$ the 12.5 kHz isn't compatible at all with the frequency deviations you post. $\endgroup$ – Marcus Müller Sep 19 '19 at 19:32
  • $\begingroup$ @MarcusMüller thanks for the comment, why do you think so? Difference between -3 and +3 deviations is ~4 kHz. As I can see, they fit 12.5 kHz bandwidth. $\endgroup$ – flipback Sep 20 '19 at 16:37

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