Estimation of the characteristics of power line channel is a pre-requisite for successful implementation of any power line communication system. This paper presents a method to estimate the forward voltage gain scattering parameters (S21) of an indoor power line using only the input port reflection coefficient (S11). The measured input parameter with one/two load placed at the output suffices to estimate the S21 as far as frequency selectivity is concerned. The positions of notches can be estimated within a limit of error with positive and at times high correlation between the experimental and evaluated S21 parameters. The method is validated for a number of practical networks, and also for random channels with different types of loads and cables found in the papers. The procedure can be incorporated in estimating the channel for mitigating the related problems.