Spectrum Engineering Reports

This is the fourth part of a four-part report containing tabulations and graphs of transmission loss data resulting from propagation experiments in the 230 - to 9200-
MHz frequency range conducted over irregular terrain in Colorado. This part presents data obtained at a Common receiver site, located in a small grove of cottonwood
(Populus deltoides) trees, over propagation paths varying in length fro 0.5 to 50 km.

Key Words: UHF propagation data, irregular terrain, UHF
propagation through trees

This report documents a digital computer program for computing the propagation of LF and VLF radio waves using the wave hop theory. It supersedes NBS Report 8889. The documentation includes a description of the physical model, detailed mathematical formulas, a main function flow chart, a listing of the FORTRAN source deck, and the input and output of a sample case.

This report summarizes measurements of tropospheric transmission loss and its long-term variability for nearly 800 paths in various parts of the world. The measurements were made at frequencies from 40 MHz to 10 GHz over distances which range from 10 to 1000 km. Terrain profiles and cumulative distributions of both observed and predicted losses are plotted for more than 500 of these paths. A preliminary analysis of differences between observed and predicted values is included.

Key Words: Cumulative distributions, location variability, long-term variability, measurements, predictions, tropospheric propagation.

After a brief description of the significance of the radio refractive index and its variation in the lower troposphere, a catalog of fading mechanisms is presented. Attention is directed to the supporting refractive index structure, the characteristics of the fading signal, and the available remedies. The phenomena of multipath fading are described, and the theoretical amplitude distributions are presented. Diversity reception (frequency or space) is outlined for reducing the fading due to multipath. Specific expressions are given for determining the frequency or space separations. Successful remedies for microwave fading that are keyed to specific fading mechanisms also constitute a means of measuring the characteristics of the prevailing meteorological conditions. Specific expressions are given to accomplish this for the multipath and diffraction fading mechanisms.

This is the second part of a four-part report containing tabulations and graphs of transmission loss data resulting from propagation experiments in the 230 to 9200 MHz frequency range conducted over irregular terrain in Colorado. This part describes data obtained at a single common receiver site at Fritz Peak, Colorado, over propagation paths varying in length from 3.0 to 120 km.

This is the third part of a four-part report containing tabulations and graphs of transmission loss data resulting from propagation experiments in the 230- to 9200- MHz frequency range conducted over irregular terrain in Colorado. This part describes data obtained at a common receiver site, which is located on a high mesa near Golden, Colorado, over propagation paths varying in length from 0.5 to 80 km.

This report is a presentation in two volumes of measurement techniques, data, comparisons, and conclusions obtained from a UHF propagation measurement program at 230 and 415.9 MHz. Antenna heights were 3 m or less above ground. Vertical polarization was used, and the antennas were omnidirectional in the horizontal plane. The terrain was generally rocky, hilly, and relatively free of trees. Path lengths varied from 2 to 45 km. Volume 1 describes the equipment, techniques, and results and presents data from the Wyoming area, including some buried antenna tests. Volume II presents data obtained in Idaho and Washington.

The technical and operating characteristics of meteor burst systems of importance for spectrum management applications are identified. A technical assessment is included, which identifies the most appropriate frequency sub-bands within the VHF spectrum to support meteor burst systems. The electromagnetic compatibility of meteor burst systems with other equipment in the VHF spectrum is determined using computerized analysis methods for both ionospheric and groundwave propagation modes. It is shown that meteor burst equipment can cause and are susceptible to groundwave interference from other VHF equipment. The report includes tables of geographical distance separations between meteor burst and other VHF equipment which satisfy interference threshold criteria includes tables of geographical distance separations between meteor burst and other VHF equipment which satisfy interference threshold criteria.