The performance of trellis-coded FSK modulation with noncoherent detection is presented, as applicable to a frequency-hopped spread spectrum communication system or a conventional FSK system. Nonorthogonal tone spacing is considered as a parameter to control bandwidth occupancy of the hopped signal and to allow an increased number of users. Soft decision decoding with a maximum metric decoder is employed. The metrics considered are the energy metric with and without perfect jammer state information as well as a practical self-normalized metric that compensates for jamming or interference. Performance analyses for full and partial band, and both noise and multitone jammings are presented. For nonorthogonal tone spacing, the signals are correlated, and so Chernoff bounds on the pairwise error probability for energy detectors with correlated signals are presented and evaluated. These bounds supplement earlier performance estimates for trellis coded FSK. To assess the tightness of the bounds, simulations have been carried out, with results that come within 1 to 3 dB of the bounds. System performance is evaluated for 2, 4 and 8-state trellis codes with tone spacings of 1/3T, 1/2T, 2/3T and 1/T Hz.>