Contents: VHF atmospheric studies and communications and navigation systems; The definition of scintillation index and its use for characterizing ionospheric effects; Summary of properties of F-region irregularities; Application of the statistics of ionospheric scintillation to VHF and UHF systems; Special problems in scintillations; and Propagation delays of VHF waves.

Contents: VHF atmospheric studies and communications and navigation systems; The definition of scintillation index and its use for characterizing ionospheric effects; Summary of properties of F-region irregularities; Application of the statistics of ionospheric scintillation to VHF and UHF systems; Special problems in scintillations; and Propagation delays of VHF waves.

Contents: VHF atmospheric studies and communications and navigation systems; The definition of scintillation index and its use for characterizing ionospheric effects; Summary of properties of F-region irregularities; Application of the statistics of ionospheric scintillation to VHF and UHF systems; Special problems in scintillations; and Propagation delays of VHF waves.

In order to provide a state-of-the-art survey of amplitude fluctuations produced by irregularities at F-layer heights in the ionosphere, a survey and review of scintillation phenomena was produced. The survey starts with a definition of scintillation index and a means of characterizing the effect of the amplitude fluctuations on transmissions from a satellite beacon. Various mechanisms proposed for the origin of the irregularity structure are reviewed in light of the observations. The translation of the geophysical information into engineering terms is made so that both depth of fade as a function of latitude and fading rate can be determined; these in turn are used to determine percentage of time scintillations will be a problem at various locations. Characteristics of scintillation dictate modulation systems to be specified for communication and navigation systems employing synchronous satellite beacons at VHF and UHF. Specific problems are addressed. These include low angle or tropospheric scintillations, polar observations, and equatorial irregularities. Variations of scintillation index with magnetic index, angle of elevation, and frequency in these regions as well as middle latitude areas are given. Another atmospheric effect on satellite transmissions is discussed in the final chapter, that is, propagation delays of VHF waves produced by the time delay of radio waves traversing the ionosphere. (Author).