ECLIPSE OF SUN

Dominion, Volume 24, Issue 221, 15 June 1931, Page 8

ECLIPSE OF SUN

Radio Waves Affected TESTS IN PACIFIC Special teste organised by the. Department of Scientific and Industrial Research to investigate the effect of the total solar eclipse of last October on wireless waves, have been reported by Dr. M. A. Barnett. In general, he says, the eclipse produced a partial return to night-time conditions as far aa the transmission of wireless waves was concerned, and changes in signal strength followed fairly closely the changes in the amount of radiation reaching the atmosphere from the sun. There were indications, however, that the changes in signal strength came a little later than the change in radiation at the place half-way between the sending and receiving stations. Scope of Tests Limited. The scope of the teste which could be arranged was limited by various factors. In the first place, the path of totality crossed the Pacific Ocean, and the choice of observing stations was restricted, particularly as not all the islands are equipped with apparatus. Secondly, it was not possible to send observers with special equipment to any of the islands,, and, moreover, the distance of transmission was inevitably considerable in many cases. Special transmissions were arranged, however, by radio stations at Wellington, Apia, Suva and Papeete. The receiving stations interested in the experiments were numerous, and were dotted round and in the Pacific and all over New Zealand. The majority of the transmission lines crossed the path of totality. Summary of Effects. In his summary, Dr. Barnett says that the results were in general accord with those experienced during previous total solar eclipses. No effect definitely attributable to the eclipse was observed on long waves, although on the Rugby-New Zealand transmission a definite increase in strength occurred during the eclipse period. On the 850' and 800 metre wavelengths an effect equivalent to a partial return to night time conditions was shown for transmission distances lying between 600 and 1200 miles. This effect was noticeable whether the transmission path actually crossed the line of totality or not. The maximum change in the signal strength occurred approximately at the time of minimum eclipse effect between transmitter and receiver, although in certain extreme cases the records indicated a lag of as much as thirty minutes between the two phenomena. In general, no eclipse effect was observed on short waves, except in certain cases on a wavelength of 52 metres, when a partial return to night time conditions was definitely indicated. In. this case also the maximum effect on signal strength either coincided with or lagged slightly behind the maximum of the eclipse at a point midway between transmitter and receiver. , . » During the tests records wore kept of the strength and persistence of almospherics, but an eclipse effect was found only in the case of reception, on 850 and 800 metres wavelength at points in the neighbourhood of totality, when a slight increase in the strength of atmospherics was observed during the’maximum of the eclipse.