def generate_freqs(self, f_start, f_stop):
        """
        returns frequency array [f_start...f_stop]
        """

        fch1 = self.header[b'fch1']
        foff = self.header[b'foff']

        #convert input frequencies into what their corresponding index would be
        i_start = int((f_start - fch1) / foff)
        i_stop  = int((f_stop - fch1)  / foff)

        #calculate closest true index value
        chan_start_idx = np.int(i_start)
        chan_stop_idx  = np.int(i_stop)

        #create freq array
        i_vals = np.arange(chan_stop_idx, chan_start_idx, 1)

        freqs = foff * i_vals + fch1

        return freqs
returns frequency array [f_start...f_stop]