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ESSA

United States. Environmental Science Services Administration

Published: 1966

Total Pages: 8


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February issue includes Appendix entitled Directory of United States Government periodicals and subscription publications; September issue includes List of depository libraries; June and December issues include semiannual index
A subsystem is described that can be added to existing radio distance measuring systems, such as SHIRAN, to increase the accuracy. The modification gives the accuracy characteristics of optical ranging systems but requires light transmission in only one direction over the path being measured. The optical subsystem can be used as seeing conditions permit, and when it cannot be used the radio system performance is not affected. Available components and technology indicate operational ranges up to several hundred kilometers.
The definition of noise factor, F, is reviewed and the mathematical bases for several methods of measuring noise factor are presented. Error analyses are given to determine: (1) the noise source temperatures, which minimize the noise factor measurement error, (2) an analytic expression for the expected error in F as measured by the CW methods, and (3) an analytic expression for the expected error in F as measured by the Y-Factor Method. A hypothetical receiver (of assumed characteristics) is used as a comparative example to elevate the errors to be expected in F as measured by the CW Method and by the Y-Factor Method. The importance of bandwidth as a criterion of receiver performance is stressed. The effect on the measured F produced by a change in receiver gain-bandwidth produced by a change in received gain-bandwidth produced by a change is receiver gain-bandwidth produce is considered briefly. A preliminary calculation of the source temperatures actually seen by the receiver input completes the report. The appendix is a procedural outline for measuring a receiver's noise factor by: (1) automatic noise factor meter (ANFM), (2) CW Method, and (3) Y-Factor Methods. This outline indicates the characteristics required of the test equipment and tells how to obtain the necessary data.
This report describes a radio investigation of traveling ionospheric disturbances carried out near Boulder, Colorado, over a 1-year period from June 1967 to June 1968. The three-dimensional motions of F2 layer disturbances were measured by the high frequency Doppler technique with spaced transmitters and at several probing frequencies. Horizontal motions were determined by cross-correlating three signals on frequencies near 5 MHz, whose reflection points were approximately at the corners of a horizontal equilateral triangle with 40-km sides. Vertical motions were determined from cross-correlation of signals on frequencies of 3.3, 4.0, and 5.1 MHz, whose reflection points were aligned vertically.