204 BELL SYSTEM TECHNICAL JOURNAL 



kilometers) from the transmitter but they no doubt exist at all ranges. 

 It is certain that both reradiating trees and ground irregularities pro- 

 duce them. By mounting the receiving set with manual recorder in a 

 light truck equipped with superballoon tires we have been able to ob- 

 tain continuous records of field strength as the truck is slowly (2 to 5 

 miles per hour) driven along the roads in the neighborhood of the trans- 

 mitter. Seven of these records and a map of the country are given in 

 Figs. 4 to 6. The records are made by recording the variation in set 

 gain necessary to hold the set output constant versus the distance 

 traversed. They have all been reduced to decibels above one micro- 

 volt per meter. The transmitter site was the Beer's hill one, later 

 described, and the records were obtained this year. They are all for a 

 vertical transmitting antenna; the corresponding results for a hori- 

 zontal antenna are complicated by the almost universal presence of 

 horizontal conductors along the roads. These wires scarcely affect 

 vertical transmission. 



As the map indicates, the seven records were taken at distances 

 from two to six miles (air line) from the transmitter. Six were taken 

 along public highways, the seventh was taken in a private field. Of 

 the six, five were taken along roads substantially radial to the trans- 

 mitter, the sixth along a tangential road. 



Record "^" was taken along a new road running northwestward 

 from Matawan, N. J. The direction of feed of these records is from 

 left to right, and the arrow indicates that the car was driving north- 

 westward, away from the transmitter. This is a radial road and, 

 being new, is not bordered by straggling trees. It covers 1.7 miles of 

 gently rolling country without steep cuts. 



A correspondence of field intensity with topography is to be expected, 

 the favorable addition of direct and reflected radiations being facili- 

 tated on slopes facing towards the transmitter and being militated 

 against on slopes facing away from the transmitter. Since the slopes 

 are often short this will put the field maxima near their tops and this 

 is what is found. This record shows this effect perhaps better than 

 any of the others; a profile of the land is included. Profiles are not 

 drawn in on the remaining curves as the country is mostly so irregular 

 that profiles are misleading. Where this topographical coincidence 

 occurs it is noted on the curve. 



As the set is carried past them, trees, wired houses, and the like 

 make their presence known on the record. Extended areas of trees, as 

 woods and orchards, usually involve a marked absorption of signal 

 intensity which, however, does not extend much beyond their bound- 

 aries. 



