THE SU2ST AND THE ATMOSPHERE STETSON 



161 



on radio communication could be measured. After a few years' 

 observations, it appeared to be evident that when solar activity de- 

 creased, the field strength of a Chicago broadcasting station observed 

 in Boston notably weakened, whereas as sunspots became less numer- 

 ous there was a marked increase in the intensity of the radio waves 

 from Chicago. A similar investigation carried on during the decline 

 of sunspots from 1930 to 1932 between Chicago and the Perkins 

 Observatory of Delaware, Ohio, yielded data to indicate that with a 

 decrease of sunspots from a monthly average of 60 at the beginning 

 of 1930 to a monthly average of about 10 in 1932, radio reception in- 

 creased six-fold in its intensity. 



Let me hasten to point out that this does not necessarily imply a 

 600 percent decrease in the ionization of the Kennelly-Heaviside layer 

 over this interval, for it appears probable that a much smaller change 

 in the percentage of ionization could so appreciably alter the degree 

 of the angle of reflection at the ionized layer as to increase materially 



100 

 90 

 60 

 70 

 60 

 50 

 4*0 

 30 

 20 

 10 

 



_G-ood Distaace_Jj/! 

 Receptioa 



67 



"Peaks of Secoattary Cycle 



Good Long-Distance. 

 Receptioa 



//IZ0-15O MILES PROM;„ y 



1923 1924 1925 192& 1927 1928 1929 1930 1931 1932 



FlGUKE 3. 



-Solar activity serves as a basis for predicting quality of radio reception for broadcast frequencies. 

 The vertical scale represents sunspot numbers. 



the strength of a wave of a fixed frequency over a fixed path as re- 

 ceived at any given point. 



Let us take an illustration from the sporting world. Suppose we 

 were in a squash court and attempted to place a tennis ball at a pre- 

 determined spot on the court by a serve directed to the ceiling. If we 

 judiciously direct our serve, we may land the ball at its desired destina- 

 tion by a reflection from the ceiling of the court. If now, the ceiling 

 should be raised or lowered by even a relatively small amount, the 

 same stroke would result in landing the ball far from its mark. Fol- 

 lowing this analogy, a radio receiver may be at an optimum position 

 for receiving a broadcast wave reflected from the ionized layer. Let 

 the ceiling of reflection of this wave be altered either in height or in 

 its ionic content, thereby increasing or decreasing the ionization present, 

 and the wave may arrive at the earth so far from our receiver that we 

 get notably bad reception. The radio, therefore, becomes a sensitive 

 and extremely useful tool in recording changes of degree of ionization 



