FSK demodulator .vi uses Mod_Max_Eye.vi to estimate the optimal sample location Ɩ at which SNR is highest. A transmitted packet consists of preamble bit sequence of [101010…], byte synchronization word followed by message bits. Synchronization word is used to lock to the start of massage and parse the information bits. Once information bits are extracted bit error rate is computed by comparing the obtained bit sequence with the actual modulated bit sequence. Developed graphical user interface of RTL-SDR receiver is shown in figure-9.
Figure 8: Spectrum of the signal at the output of various signal processing blocks and the eye diagram of the demodulated signal indicating the quality of the received signal.