Abstract. Remotely sensed microwave reflection was measured concurrently with standard magnetotransport in photo-excited high mobility GaAs/AlGaAs heterostructure. Experiments indicate strong reflection resonance on both sides of the magnetic field axis for linearly polarized microwave/terahertz photo-excitation over the examined frequency 30 < f < 330 GHz band. In addition, there is evidence for electronic heating in the vicinity of cyclotron resonance (CR), which is indicated by reduced amplitude of the Shubnikov-de Haas oscillations. Effective mass extracted from the measurements was found to equal the CR mass within experimental error.