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BELL SYSTEM TECHNICAL JOURNAL 



always worse. The remaining observations were confined to wave- 

 length ratios of 1.5 to 1 and less. A comprehensive set of records was 

 obtained for moderate to small wave-length spacings, down to 1 per 

 cent difference. These records are all for vertical polarization. The 

 few records taken on horizontal polarization happened to be obtained 

 when the horizontal fading was much worse than the vertical fading 

 and the records are too rough for good comparisons. 



For these small wave-length-difference records the types of fading 

 are more likely than not to be similar on the two wave-lengths. That 

 is, the fading rate and amplitude excursion will average up much the 

 same. More rarely, there will be a similarity between the two fading 

 tracks which is evident to the eye, sometimes as a "retarded" simi- 



20 



- 10 



6:30 A.M. 

 EASTERN STANDARD TIME 



Fig. 9— Comparison of simultaneous fading on two well spaced wave-lengths, 

 vertically polarized transmission. 



larity. Occasionally, and usually on the roller type of fading, there 

 will be a marked coincidence between the two records; this coincidence 

 will be better the milder the fading and the smaller the wave-length 

 spacing. Genuine identity was never recorded on different wave- 

 lengths even down to 1 per cent difference. With scintillation, coin- 

 cidence was difficult to demonstrate; a similarity on the major swings 

 was all that was shown. 



Figure 9 shows a very marked difference between 4.7 and 3.0 meter 

 fading. This is one of our most contrasty records. Figure 10 shows 

 very slow fading, on two occasions, with wave-length differences of 



