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The paper compares a Kalman-filter channel estimator with an alternative and much simpler estimator, for a synchronous serial data-transmission system operating at 9600 bit/s over a model of a voiceband HF radio link. A 16-level QAM signal is transmitted over the voiceband link, the latter having two independent Rayleigh fading sky waves, with a relative transmission delay of 2 ms and a frequency spread of 1 Hz. Five arrangements of the Kalman estimator and two arrangements of the alternative estimator are studied. Following a description of the various systems, the results of computer simulation tests are presented, comparing the accuracies of the estimates of the sampled impulse response of the channel given by the different estimators. It is shown that the alternative estimator is potentially much more cost-effective than the Kalman estimator.