RADIO BROADCAST COVERAGE OF CITY AREAS 129 



Street, New York City. It was found that with the limited wave- 

 length range then open to broadcasting, radiation from the station 

 was relatively poor. Measurements of the field strength delivered to 

 a field laboratory located at Cliffwood, N. J. (on lower New York Bay), 

 were made which gave the results shown in Fig. 6. The radiation 

 was found to be sharply selective with respect to frequency, and to 

 drop to a very low value at 400 meters. This happened to have been 

 the wave-length assigned to the station at the time. When it became 

 possible to shift the station to a longer wave-length, radiation was 

 greatly improved, as indicated by the curve. The study made on this 

 station was the first to disclose the fact that it is possible to have the 

 building too high for the efficient radiation of certain frequencies. 



As a result of this work it was possible to predict the probable 

 occurrence of a similar effect in the case of a station which the City 

 of New York desired to establish on the Municipal Building. Tem- 

 porary antennas were erected and radiation from them measured at 

 Cliffwood, N. J., using a transmitting oscillator of 100 watts. The 

 results of these measurements are given in Fig. 6. The radiation was 

 found to be a minimum in the vicinity of 360 meters, which was very 

 nearly the wave-length which at that time was to have been assigned 

 to this station. The establishment of the station at this location 

 obviously could not be recommended until at a subsequent time when 

 a longer wave-length was made available. The station is now operat- 

 ing on 526 meters, which is seen to be fairly well up on the radiation 

 curve. 



In both of these cases experiments were made with a number of 

 different antenna arrangements and with different methods for driving 

 the antenna and effecting the ground connection. None of the modi- 

 fications, however, materially shifted the frequency of minimum 

 radiation. This minimum occurs when approximately one quarter of 

 the wave-length equals the height of the building. Measurements 

 made upon buildings of lower heights have shown that for the usual 

 broadcast wave-lengths heights of the order of 200 ft. are entirely 

 satisfactory. The antenna of WEAF (which has been located for the 

 past several years on the building of the Bell Telephone Laboratories, 

 463 West Street, New York), and that of WCAP, in Washington, are 

 on buildings which put them at about this height above the street. 

 They both have normal radiation characteristics. 



Distribution from Suburban Locations 



In order to determine the distribution over New York City which 

 might be effected from locations outside of Manhattan Island, experi- 

 9 



