Unknown signal between 424.000MHz and 425.000MHz
Tetra band used by the bus company 'De Lijn'. Doesn't sound typical. Possibly MPT1327.
IQQuadrature signals form the basis of complex RF signal modulation and demodulation, both in hardware and in software, as well as in complex signal analysis. link: https://mega.nz/#!Ps8yRRoC!7gUEhd_Y8Pv_5GxfkRV8YgeAMocYm9muxxYlJ2X1nu0