This paper reports on results obtained by statistically processing measurements made in two work places in and near the city of Atlanta. One of these was a high-rise office building in downtown Atlanta and the other was a single-story office/workplace in Norcross, Georgia. The measurements are distinguished by virtue of the fact that they consist of frequency domain measurements of the complex channel transfer function. The results of processing the raw channel transfer function data to obtain mean delay and multipath spread data are also presented.>

A major source of propagation outages on microwave line-of-sight (LOS) links is multipath fading caused by steep negative refractive index gradients. This paper develops a complete transfer function characterization of refractive multipath on LOS links. The results clearly show the dependence of discrete path amplitudes and delays on receiver height, transmitter height, refractive index gradient, layer height and ground range.

Using some basic concepts of ionospheric propagation, multipath and Doppler spread calculations are obtained for the HF ionospheric communication channel. Because of sensitivity to the solar control mechanism, the Doppler spread results are found to demonstrate a pronounced dependence on time of day and operating frequency. The practical consequences of these calculations are discussed in detail. This includes the definition and generation of the "Doppler reduction factor," comparable to the "multipath reduction factor," which can be used to determine the appropriate operating frequency on a given HF link.