A method for searching a frequency band to locate a channel. The method includes the steps of setting an initial frequency and a first frequency step; determining a frequency point based on the initial frequency and the first frequency step; determining whether the frequency point satisfies a first condition, which is continuously detecting a horizontal signal a predetermined number of times. When the first condition is satisfied, the frequency point is recorded as an entrance point. A second frequency step based on the entrance point determines a second frequency point, wherein the second frequency step is less than the first frequency step. It is then determined if a channel exists at the second frequency point. The entrance point is recorded as the updated initial frequency for the next search. The described steps are repeated for the entire frequency band.