A 60-FOOT PARABOLIC ANTENNA FOR PROPAGATION STUDIES 1203 



Fig. 5 — Antenna scanning motors. 



0-30^ 



Fig. 6 — Feed horn dimensions. 



measure these properties at 9.4 kmc to get some idea of how good the 

 mechanical tolerances actually are. 



The first requisite for making antenna measurements is a suffi- 

 ciently uniform incident field. The source producing this field must be 

 located at a distance of at least 2b VX, (b is the paraboloid diameter), 

 which means a distance of about 0.6 mile at 460 mc, six miles at 4 kmc, 

 and thirteen miles at 9.4 kmc. An obvious and convenient place for the 

 sources was at Murray Hill, 22.8 miles away, which is on the transmis- 

 sion path to Pharsalia. Having located the sources at a suitable distance 

 it was then necessary to test the incident field for uniformity. A 64-foot 



