Since TV white space systems must not cause interference to TV broadcasting performance, a propagation model for the interference estimation is very important. In this paper, a propagation experiment has been conducted using a TV white space station to develop a propagation model which estimates the maximum received power for interference evaluations. From received power measurements within several kilometers from the station, the maximum power matched the limitation of an envelope curve model based on a two-path model with a ground profile. By verifying the model using all measured data, it is proved that the proposed model is applicable for interference evaluation of TVWS systems.