Special Evaluation for Pedestal-Level Stability of Height-Finder Radars on Temperate Towers (77-05),

摘要

Pedestal-level stability of the AN/FPS-6 family height finder radars in ADCOM was investigated from September 1974 to February 1977 in connection with routine evaluation projects. The investigation was motivated by instability problems encountered at Z-96, Almaden AFS, California, during a routine height finder evaluation project, and the data collected by the evaluation team were used in the investigation. Those data led the evaluation team to correctly conclude that solar heating was associated with the problem. During a 1974-77 investigation, pedestal-level instability problems were encountered only with temperate towers, which have exposed legs. Deviations of the pedestal plane exhibited a diurnal pattern that was strongly correlated with the sun, except at one site, Klamath, California. The information from Klamath was obtained separately from this study and is inconclusive. A plausible explanation for all the findings (neglecting Klamath) is that the tower legs are unequally exposed to the sun so that the unshaded legs expand more than the others, thereby shifting the antenna pedestal. This explanation fits well with the observations whereby deviations were greatest when the sun was high in the sky on clear, calm days, and excursions approached an angular value of 1 mil.