This paper contains results of a measurement program on 751 Mc/s and 9.2 Gc/s using a long mountain-obstacle diffraction path in Colorado. Data are analyzed and evaluated in terms of long· term and short-term variability, correlation coefficients between carrier envelopes received on spaced antennas, and comparison of a priori predicted and measured cumulative distributions of hourly transmission loss medians. Results show beuer agreement between predictions and measurements on 751 Mc/s than on 9.2 Gc/s. Short-term (within-the-hour) variations in signal level on 751 Mc/s can be characterized as prolonged space-wave· fadeouts, whereas such variations on 9.2 Gc/s verv frequently show characteristics of a Rayleigh-distributed signal.
This report describes many of the UHF propagation characteristics between aircraft or satellites and buried antennas. A vertical monopole was used as a reference antenna, and the propagation characteristics of an annular slot and other antennas, omnidirectional in azimuth, were measured. The effects of reflecting planes used in conjunction with buried elementary antennas were measured. Site power gain patterns were measured from the buried antenna site at elevation angles up to 70°. These tests were made over a reasonably smooth plane, on paths of 0.03, 0.06, and 1 km, and at various transmitting antenna heights, with a helium-filled ballon. In some of the tests security fences were used.
Height-gain measurements conducted previously over a mountain-obstacle diffraction path at 751 MHz are re-evaluated in terms of the calculated lobe patterns.
The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the na¬ tional standards of measurement and the provision of means and methods for making measurements consistent with these standards; the determination of physical constants and properties of materials; the development of methods and instruments for testing materials, devices, and structures; advisory services to government agen¬ cies on scientific and technical problems; invention and development of devices to serve special needs of the Government; and the development of standard practices, codes, and specifications. The work includes basic and applied research, development, engineering, instrumentation, testing, evaluation, calibration services, and various consultation and information services. Research projects are also performed for other government agencies when the work relates to and supplements the basic program of the Bureau or when the Bureau's unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover.
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