Performance of some Rake modems over the non-disturbed wide band HF channel

The author presents performance evaluations for four Rake modems used to communicate over the wideband (e.g. 1 MHz) HF channel. Attention is confined to performance for the nondisturbed HF channel. Consideration is given to the impact of mode Doppler shift and multipath spread due to dispersion. The effects of additive noise, self-noise, and imperfect channel measurements are included. Results are presented for decision-directed, parallel probe, serial probe, and DPSK Rake modems. Performance to within 1-3 dB of the additive white Gaussian noise channel is predicted, depending upon the modem and the channel dispersion, if the Doppler shift of the modem can be tracked to within 0.1 Hz