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The performance of wideband HF long distance communication systems is heavily influenced by the ionosphere conditions because of the function of the ionospheric layer as a reflector for HF radio waves. There are several diurnal variations of the ionosphere during the day and night and disturbances in ionopheric layer especially in the low latitude region called Equatorial Spread F (ESF). This paper describes a measurement result to find delay spread and rms delay spread of wideband HF radio communication system in Surabaya -Merauke link for daytime and nighttime channels. Pseudorandom Binary Sequence (PRBS) signals are transmitted from Surabaya (07 o 15' S 112 o 45' E) and received in Merauke (08 o 30' S 140 o 27' E). The result of this paper should be compared to the ionosphere conditions provided by ionosonde operated in Kupang (09 o 19' S 10 o 57' E), approximately in the middle of the HF link.

Studies have been reported in the literature on High Frequency (HF) radio channels in mid-latitude areas more frequently than in low latitudes, where the ionospheric channels might behave differently. This paper reports a statistical model of HF sky wave channel complex impulse response and its parameters, i.e., channel gain, path gain, phase shift, and delay spread statistics, derived from both simulation and measurement on a 3044 km link in Indonesia. Evaluations show that multipaths observed with respect to their propagation delays form multiple clusters corresponding to different propagation modes. The channel gain is found to be Rayleigh distributed, whereas the rms and maximum delay spread exhibit Rayleigh and Gaussian distributions, respectively. This model can be used in performance evaluation of digital communication schemes in low-latitude HF channels.

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