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° 15' S 112° 45' E) and received in Merauke (08° 30' S 140° 27' E). The result of this paper should be compared to the ionosphere conditions provided by ionosonde operated in Kupang (09° 19' S 10°57' E), approximately in the middle of the HF link.