Annual progress report to United States Information Agency, Voice of America, Contract IA-14219 -23, September 1969 ­June 1970

Alfred F. Barghausen et al.

Abstract: In this period the HF timeshare program was updated to include circuit reliabilities under Task I. For Task II an investigation showed that variation of foFl could be satisfactorily represented by a formula expressing the dependence of foFl on solar zenith angle, smoothed sunspot number, geomagnetic latitude, and a seasonal factor. The occurrence of spread F was numerically mapped from the F-notations on ionosonde scalings. Maps for January, April, July, and October of 1958 and 1964 were produced under Task III. The numerical maps of spread F used modified dip latitude and the standard deviations of residuals ranged between 10.9 and 14.8 percent. As Task IV system performance predictions were provided six months in advance for 200 VOA broadcast facilities. Among other parameters the most reliable mode, the field strength, and the LUF were predicted. Other predictions gave the optimum assignment of 33 antennas at a given location and short-term predictions a month in advance for 28 circuits. Task VI was a comparison of observations with the ITS predictions at 26 monitoring site s over the period September 1969 to April 1970.

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