A 60-Foot Diameter Parabolic Antenna 

 for Propagation Stndies* 



By A. B. CRAWFORD, H. T. FRIIS and W. C. JAKES, JR. 



(Manuscript received February 2, 1956) 



A solid-surface parabolic antenna, sixty feet in diameter and of alumi- 

 iium construction, has been erected on a hilltop near Holmdel, New Jersey. 

 This antenna can be steered in azimuth and elevation and was specially 

 ih signed for studies of beyond-the-horizon radio propagation at frequencies 

 of 460 mc and 4,000 mc. 



The electrical properties of the antenna and the technique of measure- 

 ment are described; construction and mechanical details are discussed briefly. 



IXTRODUCTION 



Studies in recent years have demonstrated that transmission of useful 

 amounts of microwave energy is possible at distances considerably far- 

 ther than the horizon. ^ The exact mechanism responsible is not as yet 

 completely understood, although scattering by atmospheric irregularities 

 seems to play a significant part. A program to study the nature of these 

 effects has been started at the Holmdel Laboratory. An important and 

 necessary tool for this work is a steerable antenna having unusually high 

 gain and narrow beam width. Such an antenna has been built, and it is 

 the purpose of this paper to describe its design and the methods used to 

 measure its radiation properties. 



DESCRIPTION OF THE ANTENNA 



The antenna is a 60-foot diameter paraboloid made up of forty-eight 

 radial sectors, each constructed of sheet aluminum. Each sector is held 

 to the correct doubly-curved surface by reinforcing ribs, and all are 

 fastened to a central hub eight feet long and thirty inches in diameter. 

 During assembly, the axis of the paraboloid was vertical; thus no scaf- 



* This work was supported in part by Contract AF 18(600)-572 with the U.S. 

 Air Force, Air Research and Development Command. 



' Proc. I.R.E., October, 1955, contains many papers by workers in this field. 



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