Eclipse of the Sun

Radio Record, Volume II, Issue 36, 22 March 1929, Page 25

Eclipse of the Sun

Effect on Radio DURING the recent total eclipse of the sun arrangements were made by the Radio Research Board in Great Britain for a number of wireless observations to be made in order that "the effect of the eclipse on wireless could be studied. The experiments were made on long waves (12,000 to 14,000 metres), and on medium waves (300 to 500 metres). The long wave observations were planned to include respectively signals which crossed the band of totality, those that travelled as nearly as possible along it, and those that were wholly outside of it. Apparatus was used for analysing long-wave propagation to show the relative effects of attenuation, the relation between the phases of the ground and down-coming waves, and any abnormal polarisation of the down-coming wave. ‘The effect of the observations was to show the influence of the eclipse as that of a minor sunset, producing only the preliminary phenomena of a normal sunset, and suggesting that totality did not last long enough to enable the complete effects to occur. The effects were not confined to the totality band, but were noted in the transmission which was outside of it. This is in harmony with an observation made previously in respect to sunset transmission. Wits regard to the medium waves, the observations showed a great increase in the intensity of the downcoming waves, which was interpreted as being due in part to the increased height of the atmospheric stratum from which the waves were reflected, and in part to the rapid deionisation of the lower layers of the asmosphere on the removal of the ironising agents due to solar rays. The period during which these efforts lasted varied from twenty to fifty minutes at different stations, while it took nearly two hours for the moon’s shadow to pass across the sun, suggesting that wireless methods may not be able to detect these effects before quite an appreciable fraction of the sun’s radiation had been cut off. Wor some reasons all the stations showed that on the morning after the eclipse night-time conditions seem to persist for a long time after sunrise, Direction-finding observations seemed to show that during the eclipse the normal night properties of the reflecting atmospheric layer were temporarily restored, as was suggested independently by the observations on trans-missions.-"Sydney Morning Herald." -- ~