Abstract: I will present the results of experimental and theoretical study of irregular, tetrahedral microwave networks consisting of coaxial cables connected by T-joints. The comparison of the experimental and theoretical results shows that microwave networks can simulate quantum graphs with time reversal symmetry. In particular, the spectra of the microwave networks are used to study the periodic orbits of the simulated quantum graphs. I will also present experimental study of directional microwave networks consisting of coaxial cables and Faraday isolators for which the time reversal symmetry is broken. In this case the experimental results indicate that spectral statistics of directional microwave networks deviate from predictions of Gaussian orthogonal ensembles in random matrix theory approaching, especially for small eigenfrequency spacing s, results for Gaussian unitary ensembles.