/AM.vs.(//../.v//(" R.inn) ir.i.f:rii(K\ii /am.v.v.u/w/o.v •«,'«) 



In K^-iuTal, lIuTi'fort', tlu- AiiUTtran ri-snlts arrortl with thosr 

 cil)t.iiiH'(l in l-jinland in indiratin^ (|uiti' di-fuiitfly that a larjii" pro- 

 portion of ihf st.itic ri.'ii'i\f<l on ilir lon^i-r \va\r-. i-- of tropical origin. 



Si(iN.\i. TO NoisK R.\rii) 



It is. of roiirsi", the ratio of the signal to noisi- str(.n^;th which 

 (icti'rmines the commiiniration merit of a radio transmission channel. 



Variation with Frequency. A comparison for representative summer 

 and winter months is given in Fig. 25 of the signal-to-noisc ratio 



Fig. 25 — \'ariation of signal to noise ratio with frequency. Corrected to same 

 antenna input power (68.5 K\V) in Rocky Point antenna — Reception at New South- 

 gate, England 



for the two extreme frequencies measured. Both of these trans- 

 missions were efTected from the same station, Rocky Point, and sim- 

 ilar antennae were employed. Comparison is made of the overall 

 transmission by correcting the values of the two curves to the same 

 antenna power input, the pow'er of both channels being scaled down 

 to t)8 kilowatts, the |)ower used in the telephone channel during the 

 early parts of the e.xperiment. This chart shows clearly the greater 

 stability in signal to noise ratio obtainable on the lower frequency 

 channel. While for certain perituls of the day the higher frequency 

 gives a much better ratio, it is subject to a much more severe sunset 



