The loop radius of the coincident-loop system above a polarizable half-space has a significant effect on the magnitude of the negative response and its time of occurrence. Computations are made to study this phenomenon for various values of the electrical parameters of the ground, which is described by a Cole-Cole model. An optimum loop radius is found to exist, which leads to the largest peak of the negative response. It is found that for values of the frequency parameter (c) larger than 0.5, the largest peak of the negative response occurs at a time nearly equal to the Cole-Cole time constant. Empirical formulas are deduced relating both the optimum loop radius and the largest peak of the negative response to the electrical parameters of the polarizable half-space. The above phenomena may be used as a simple and effective guide for the detection of a polarizable target and estimating its electrical parameters.