One of the key component in many GnuRadio projects is the quadrature frequency demodulator. This functionality allows to calculate the real analog output of a frequency modulated signal from the IQ-signal, which is mainly captured using HF hardware (e.g. dvb-t dongle, USRP, etc.) by a carrier frequency (band pass domain) and transform it to the base band domain. The most known implementations of the FM-demodulator are based on trigonometric functions. These functions require a high computation effort. Some implementation of “tuned” trigonometric function, which were downsized for FM-demodulation reduce the computation effort a little. A new proposal of a so called arithmetic FM-Demodulator allows to avoid completely the usage of any trigonometric function and speed up the computation process in many times. In the presentation I will introduce mathematical background for the arithmetic FM-Demodulator, show the differences and limitations to the current implementation in GnuRadio Version. Further Philipp will present our result, we had achieved in our lab.