. The Bell System technical journal . est antenna is used, the ionospheretakes charge of the signals, and separates them into an o-componentand an x-component. Each travels according to its proper law, andthe x-component reaches its lower-down mirror earlier and beats theo-component back to earth. Two echoes return instead of earlier is plane-polarized with electric vector east-and-west; thelaggard is plane-polarized with electric vector a long straight horizontal antenna is used to respond to thereturning signals. It will respond to both, if pointed north-west-
. The Bell System technical journal . est antenna is used, the ionospheretakes charge of the signals, and separates them into an o-componentand an x-component. Each travels according to its proper law, andthe x-component reaches its lower-down mirror earlier and beats theo-component back to earth. Two echoes return instead of earlier is plane-polarized with electric vector east-and-west; thelaggard is plane-polarized with electric vector a long straight horizontal antenna is used to respond to thereturning signals. It will respond to both, if pointed north-west-southeast; only to the earlier, if pointed east-and-west; only to thelater, if pointed north-and-south. All the foregoing were statements of theory at first, but thanks tothe experiments of Wells and Berkner at Huancayo, they now arestatements of data as well.^ Figure 13 exhibits a small selection fromthe data. RECEIVETRANSMIT NW-SENW-SE N-S NW- SE NW-|| NW- SE II SE NW-SE NW-SE NW-SE NW- SE =i 500- P 300- m0H0^^^tdl^!l . -^.».. l^^. 10 . loh 35m 75° WEST MERIDIAN TIME IN HOURS 12 Fig. 13—Echoes of plane-polarized signals near the geomagnetic equator.(Wells and Berkner.) Now look again at Fig. 4: formerly I asked the reader to ignoreone of the curves, but now we will compare the two. The circles andthe crosses indicate the o-wave and the x-wave respectively. One is ^ This is a good place to speak of a question which may already have occurredto many readers, viz. the question why we assume the charged particles in theionosphere to be free electrons rather than charged atoms or molecules. Werethey of atomic or molecular mass, the separation of the 0 and x echoes would beinappreciable, and the gyro-frequency later to be mentioned (page 482) wouldbe quite outside of the radio range. It is not, however, excluded that among thefree electrons there may be a great multitude of charged atoms, perhaps even manytimes more numerous than they, though much less influential. 482 BELL SYST
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