generation of random frequency signals

i need to generate a signal in the time domain and take its fft so that i get a random sequence of frequencies F=[F1,F2,....Fn-1], wer n=16.... i need these frequency to be random... and these frequencies should not be like only positive value... i need the freq to be anywhere in the circle... like any random point in the cirle.. can anyone pls give me the matlab code.... rather than a one line command like just to generate freq seq can anyone tell me how to write the signal in time domain so that i get the random freq seq??? pls help...