Download or read book Hf Communication Effects Frequency Dispersion and Doppler Shift written by R. A. Shepherd and published by . This book was released on 1965 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: This effort was part of a program of research to determine the effects of high-altitude nuclear explosions on HF radio communications, using naturally occurring disturbances to simulate nuclear distrubances. Phase-stable transmissions at 7.366 Mc over a transauroral path from Thule, Greenland and over a mid-latitude path from Fort Monmouth, New Jersey were received at the SRI field site near Palo Alto, California. Both of these paths were paralleled by step-frequency oblique-incidence ionospheric sounders. Power spectra of the received CW signals were computed, enabling the identification of individual ionospheric modes by their separation in Doppler shift. Examples of power spectra of simple and of more complex mode structures, including off-path modes, are given. Statistics of the frequency dispersion and the Doppler shifts of the Thule and Fort Monmouth signals are compiled for selected data in February, March, and June, 1964. Comparisons show that while Doppler shifts for the two paths are similar in magnitude, the frequency dispersion of signals on the transauroral path is about ten times as great as that on the mid-latitude path. (Author).
Download or read book HF Communications written by Nicholas M Maslin and published by CRC Press. This book was released on 2017-06-30 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Communications using the high frequency spectrum (2-30 MHz) have experienced a considerable resurgence. In recent years, powerful microcomputers and VLSI technology have greatly enhanced the prospects of overcoming many of the unique problems that formerly afflicted the HF systems More...designer. The aim of this book, therefore, is to provide a fi
Download or read book Propagation Impact on Modern HF Communications System Design written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development and published by . This book was released on 1986 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Space Physics and Aeronomy Ionosphere Dynamics and Applications written by Chao Huang and published by John Wiley & Sons. This book was released on 2021-05-11 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive review of global ionospheric research from the polar caps to equatorial regions It's more than a century since scientists first identified the ionosphere, the layer of the Earth’s upper atmosphere that is ionized by solar and cosmic radiation. Our understanding of this dynamic part of the near-Earth space environment has greatly advanced in recent years thanks to new observational technologies, improved numerical models, and powerful computing capabilities. Ionosphere Dynamics and Applications provides a comprehensive overview of historic developments, recent advances, and future directions in ionospheric research. Volume highlights include: Behavior of the ionosphere in different regions from the poles to the equator Distinct characteristics of the high-, mid-, and low-latitude ionosphere Observational results from ground- and space-based instruments Ionospheric impacts on radio signals and satellite operations How earthquakes and tsunamis on Earth cause disturbances in the ionosphere The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals. Find out more about the Space Physics and Aeronomy collection in this Q&A with the Editors in Chief
Download or read book Hf Communication Effects Prediction of Propagation Parameters Affecting Error Rate written by Edel M. Young and published by . This book was released on 1965 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report discusses a proposed method of predicting error rate for HF communication systems. The method is based on the long-term HF propagation prediction methods of CRPL and USARPA, and on estimates of the channel-scattering function. This function provides a basis for determining the time-and frequency-selective fading effects caused by variations in the propagation medium. Performance predictions have previously been made by computing only the S/N of the received signal. It is recommended that time spread (multipath), Doppler frequency spread, and diversity correlation also be considered. The sources of error in predicting field strength are investigated, and measurements on two paths for one year are compared with predictions. No improvement in the method of predicting field strength can be recommended. Emphasis is given to the problem of predicting all significant modes of propagation, including those associated with sporadic E. High-latitude effects are also treated briefly. (Author).
Download or read book The Effect of the Ionosphere on Communication Navigation and Surveillance Systems written by John M. Goodman and published by . This book was released on 1988 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Survey of the Effects of Ionospheric Propagation on HF Communication Systems written by W. L. Hatton and published by . This book was released on 1967 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hf Communication Effects Experimental Justification of the Gaussian Channel Model written by B. C. Tupper and published by . This book was released on 1965 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Theoretical expressions for joint probability-density and distribution functions for phase difference and log-envelope difference for a Gaussian channel are derived. Experimental data collected from an HF phase-stable transmission are compared with the theoretical densities and distributions by using the statistical parameter of correlation coefficient. An estimate of the relationship between the correlation coefficient and channel frequency spread is derived and compared with experimental data. Agreement between correlation-coefficient estimates from log-envelope change and phase change is discussed. The experimental envelope distributions of the received signal are compared with the Rayleigh, Rician, and log-normal distributions, and deviations are discussed. Alternative envelope distributions based on a conditional Rayleigh distribution are also considered. (Author).
Download or read book HF Communication Effects written by T. I. Dayharsh and published by . This book was released on 1965 with total page 93 pages. Available in PDF, EPUB and Kindle. Book excerpt: The interrelationships of particular high-latitude phenomena--E sub s, magnetic storms, complex ray paths, and field-aligned ionization--and HF oblique sounder observations from five paths for one year are analyzed in this report. Magnetic field deviations produced during magnetic storms were found to be highly correlated with ionospheric variations that occurred one to three hours after the magnetic variations. Equations relating the magnetic field variations to the ionospheric variations are developed in this report with generally favorable results. Prediction of E sub s oblique mode occurrences and MOFs from vertical sounder data is also presented in this report. The sounder data was used to plot maps of f sub o E sub s and percent occurrence. Good agreement is found between the observed oblique mode statistics on four paths and those predicted from the maps. Ray-tracing techniques were used to simulate the observed oblique ray paths from vertical -incidence sounder data taken along the oblique paths. It was found that ray-tracing techniques were remarkably accurate, considering the drastic variations in ionospheric parameters along the path. Ray-tracing techniques for modes using field-aligned ionization are also presented in this report. Time delays derived by these techniques fit remarkably well with statistics for the observed scatter-modes on two paths. (Author).
Download or read book HF Communications Systems and Technology written by John M. Goodman and published by Springer. This book was released on 1992-05-28 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt: Communications engineers, ionospheric scientists, engineers and scientists in DoD HF projects, and DoD managers will use this source to gain a working understanding of the basic theory involved in HF radiowave propagation and uses of HF technology today.
Download or read book Hf Communication Effects Simulation Instrumentation and Operation of the Field Experiment written by R. A. Shepherd and published by . This book was released on 1963 with total page 103 pages. Available in PDF, EPUB and Kindle. Book excerpt: The field-test phase of the experiment consists of an examination of six propagation paths, some of which pass through the auroral zone and some of which are south of the zone. These six paths are examined with oblique-incidence ionosphere sounders which collect propagation data between 4 and 64 Mc. Two of the paths are also studied using a phase-stable CW system for the measurement of phase and amplitude of propagated signals. The primary equipment used in the experiment, consisting of Granger Associates ionosphere sounders and of a phase-stable CW system developed by SRI, is described in this report. (Author).
Download or read book Hf Communication Effects Simulation Comparison of the Fort Monmouth palo Alt Circuit Performance with Computer Predictions written by Harry A. Turner and published by . This book was released on 1964 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observed and predicted HF propagation data are compared. Observed data were taken by obliqueincidence ionospheric sounders, the Philips sounder (November 1961 and February 1962) and the Granger Associates sounder (1963), operated between Fort Monmouth, New Jersey and Palo Alto, California. Predictions were taken from the HF propagation prediction program written by Stanford Research Institute for use on the IBM 7090 computer. The comparison was undertaken in order to find how well the computer prediction methods predict skywave propagation and where these methods can be improved. (Author).
Download or read book Hf Communication Effects Physics and Chemistry of the Ionosphere written by R. C Whitten (Jr) and published by . This book was released on 1965 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ionosphere from 50 to 700 km is discussed in an attempt to provide information of value and interest to radio communicators. Diurnal, seasonal, and solar cyclical variations of the ionosphere are considered as well as effects of diffusion, turbulence and winds, tidal and wave motions, chemical reactions, and magnetic disturbances. Ionization by extreme UV photons, solar X-rays, and Lyman-alpha and cosmic radiation are presented as functions of solar activity. The ionization and deionization processes (dissociation, recombination, charge transfer, and ion-atom interchange) that control ion and electron densities in the ionosphere are discussed. Detailed models of (1) the quiet ionosphere, (2) sudden ionic disturbances, (3) polar cap absorption events, and (4) ionospheric and geomagnetic storms are developed. Current theories of ionospheric processes and phenomena are evaluated and remaining problems of interpretation pointed out. (Author).
Download or read book Hf Communication Effects Simulation the Ionosphere Above 100 Km a Simple Model written by Robert Craig Whitten and published by . This book was released on 1964 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model of the quiet ionosphere in the altitude range 100 to 500 km for various conditions of solar activity is constructed. In order to carry out this program, a model atmosphere, i.e., profiles of temperature density, pressure, number density of the various constituents, and scale height, based on rocket and satellite measurements and on models developed by other investigators, is also developed. From the model atmosphere and from measurements of the intensities of solar ionizing radiations, ionization rate profiles are computed. Electron loss and diffusion processes and their associated rate constants are also treated, and the results are substituted into appropriately simplified forms of the continuity equation; the solutions yield the ionospheric model. E- and F-region irregularities are also discussed, and a model of electron collision frequencies in the altitude range 100 to 500 km is presented. (Author).
Download or read book Effects of Solar Disturbances on Radio Communications with Aircraft written by Joseph Horace Pope and published by . This book was released on 1972 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Combined Channel Sounding and Direction Finding Studies of HF Radio Propagation Effects Observed Over High Latitude Communication Paths written by Clive Andrew Jackson and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of the Ionosphere on Space Systems and Communications written by John M. Goodman and published by . This book was released on 1975 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
