Accurate measurements of common properties of the propagation channel is a major concern for narrow band power line communication (PLC) systems in the frequency band between 9 kHz and 500 kHz. Precise knowledge of both the attenuation and the characteristic impedance of low voltage cables are an important part of the characterization of the propagation channel. This paper presents a method for experimental assessment of these parameters. Measurement results of underground and overhead line twisted cables are obtained and analyzed as these are the most representative cables used in low voltage (LV) distribution networks. Using LCR-Meter, two variants of the measurement method are proposed to investigate the real and imaginary parts of the propagation constant. The influence on the characteristic impedance is discussed and the transmission line characteristics are presented as a function of the frequency for both types of cables. One of these variants makes use of approximations, so the effects of this approximation on the secondary parameters are outlined.