RADIO BROADCAST COVERAGE OF CITY AREAS 127 



powers of the order of five kw. and even 50 kw. is decidedly in order. 

 Such increases in power will be required if the broadcasting art is to 

 be advanced to meet the higher standards of the future. The fact 

 should be recognized that no greater interference between stations 

 will be caused by the higher power levels, providing the increase in 

 power is general among all stations. The interference difficulty arises 

 in particular cases where one station suddenly makes a large increase 

 and the others remain at their previous low power levels. 



Mention should perhaps be made that the effect of raising the trans- 

 mitter power in increasing the level of the detected signal is greater 

 than would be inferred from the discussion above. This is because 

 of the square-law action of the detector. In other words, the detector 

 output reflects the increase in power of the carrier as well as the side 

 band. In overcoming interference it is only the increase in side-band 

 power which counts. 



The ideal broadcast system from the transmission standpoint would 

 be one in which the carrier is not transmitted from the sending station 

 but is automatically supplied in the receiving sets themselves. This 

 would save power, would reduce interference between stations and 

 would reduce fading. It will be recalled that this system is being 

 used to great advantage in the transatlantic radio telephone develop- 

 ment. The practicability of employing it in broadcasting will depend 

 upon receiving set development, — upon the economy with which 

 carrier-generating receiving sets can be made and the ease with which 

 the carrier frequency can be set and maintained with the necessary 

 accuracy. 



Transmitting Station on Tall Building 



The location which naturally suggests itself for a broadcast station 

 intended to serve a city is that of its center. Such a location might 

 be expected to deliver the greatest strength of field to the greatest 

 numbers because of the coincidence between high field strengths and 

 high density of population. The other possibility, of course, is that 

 of placing the station outside of the city, with the object of obtaining 

 a better "get-away" condition, of covering a larger area and of laying 

 down a more uniform, if less strong, field over the city itself. In- 

 stances of both of these types of locations readily come to mind. 

 WEAF is a good example of a station located near the center of a large 

 city. The results of a study which has been made upon the effect 

 of moving the station to other possible locations are given below. 



Before coming to this, however, there is another important factor 

 to present and that is the effect of placing the transmitting station 



