Abstract— In this paper, we have investigated the maximumlikelihood (ML) receivers for the fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) spread-spectrum communications system with a worst case multitone jamming (MTJ) and additive white Gaussian noise (AWGN) over frequencyselective Rayleigh fading channels. Owing to the fact that the analysis of the natural logarithm of the modified Bessel function is intractable, two ML diversity-combining receivers, that are named as ML-A and ML-B receivers according to the different conditions of the approximation, have been analyzed theoretically based upon a correlated two-path frequency-selective channel model. The performance of these two receivers compared with that of other diversity-combining receivers in terms of the bit error rate (BER) has been scrutinized. Computer simulations confirm that our numerical analyses are valid. Furthermore, the ML-B receiver outperforms other receivers, while the MLA receiver is only as goo...