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BELL SYSTEM TECHNICAL JOURNAL 



Such fields, however, may be of some value for the dissemination of 

 useful information such as market reports, where the value of the 

 material is not dependent upon high quality reproduction. 



roo 



80 

 60 



340 



20 



4 6 8 10 

 Radiated Power 



20 



40 60 80 100 KW 



Fig. 5 — Showing the increase in radiated power required to increase the range 

 at which a field of 10,000 nv./m. is delivered. Curve A without absorption and 

 curve B with absorption. 



It is seen from the preceding three figures that a 5 kw. station may 

 be expected to deliver a field of 10,000 microvolts some 10 to 20 miles 

 away and a 1000 microvolt field not more than 50 miles. From this 

 it will be evident that the reliable high quality program range of a 

 5 kw. station is measured in tens of miles rather than hundreds. 



Higher Power Transmitting Stations Required 



Rough though this interpretation of field strengths is, it indicates 

 clearly the need which exists for the employment of higher trans- 

 mitting powers. The range goes up with the increase of power dis- 

 appointingly slowly. Even were no absorption present in the trans- 

 mitting medium, the range in respect to overcoming interference 

 would increase only as the square root of the increase in power. This 

 is shown in the curve A of Fig. 5. It shows that a station which 

 actually radiates five kw. of power would deliver a 10,000 ^uv./m. 

 field at about 40 miles, a 20 kw. station the same field at distance 80 

 miles. Actually with absorption present the distances are less. This 

 is shown by the curve B which gives the corresponding relations for 

 the absorption observed for suburban and country terrain. To extend 

 the 10,000 microvolt field from some 15 miles out to 30 miles would 

 necessitate an increase in the radiated power from about five to 100 kw. 



It is apparent from these relations that radio broadcasting is today 

 underpowered ; that the common 0.5 kw. station is entirely too small 

 to serve large areas adequately, and that the more general use of 



