Simultaneous measurements of propagation characteristics on noncontiguous HF channels

An experiment to investigate the relationship between channel characteristics on noncontiguous HF channels has been run on an HF path in Norway. Initial results from a limited 3 kHz bandwidth data set have focused on the reaction of the channel to sunrise, when significant Doppler spreads have been observed. It has been found that, across the operating frequency band of the experiment (/spl sim/0.5 MHz), the Doppler spreads at different carrier frequencies remain well correlated. This indicates that it is acceptable to use a constant value of Doppler spread over bandwidths of at least 0.5 MHz when testing adaptive HF systems. Further investigation will be required to determine whether this result is applicable to other forms of ionospheric disturbance; i.e. in the auroral and equatorial regions.