HARVARD ASTRONOMER EXPLAINS RADIO EVIL

For the first time in the history of radio it has been established that sun spots affect radio reception it was announced yesterday to a CRIMSON reporter by Professor H. T. Stetson at the Harvard Astronomical Laboratory.

"Solar investigations are being undertaken at the Laboratory of Astronomy during the present sunspot maximum and include the daily photography of the sun's surface. The measurement of the sun spots, which are regions of electrical disturbances or storms on the surface of the sun, is being carried out in cooperation with the Mt. Wilson Observatory, the Yerkes Observatory, and the United States Naval Observatory," Professor Stetson said.

"In connection with these investigations of the sun's surface, we have made arrangements with Station WBBM of Chicago for nightly measurement of the intensity of radio reception with a view to ascertaining just what effect these electrical storms, which might be compared to cyclones or hurricanes on the earth, have on the strength of the radio waves. By comparing the graphs of the sun spots and the radio reception we were gratified to discover that, invariably, as the number and intensity of sunspots increased, radio reception grew worse, until, at the peak of the period of sun spot activity, called the Sunspot Maximum, the radio signals reached their weakest point. Likewise, when the spots on the sun were fewest and weakest, the radio reception was best. For the measurement of radio reception we have made use of a superhetrodyne receiver with multiple stage amplification together with a self-recording galvanometer. A local oscillator with controlled output makes possible the exact calibration of the entire receiving circuit prior to each night's observations," Professor Stetson continued.

After preliminary experiments it was found that the hour from nine to ten o'clock in the evening was on the whole best suited for determining the strength of the radio signals each night. The broadcasting station, WBBM of Chicago, maintained reliable consistency in power which it transmitted and communicated with the Astronomical Laboratory concerning any departures from normal conditions. The intensity of the signal strength measured is that of the carrier wave which is not apparently affected by the modulations of the program broadcasted.

It was proven that a definite correlation exists between radio reception and sunspot activity by comparing graphs made of the results of the various experiments.

Work Began at Newton Laboratory

The quantitive measurement of the radio reception intensities was begun at the private laboratory of Mr. G. W. Pickard in Newton Centre. Last year a duplicate outfit was then installed at the Astronomical Laboratory in Cambridge and the measurements carried on there under the direction of Professor Stetson. For a few weeks simultaneous records were kept in the two places until a satisfactory reduction factor was obtained whereby the two series of data could be rendered comparable.

Another important result of the study of the radio reception is to show completely how unfounded is the popular impression that radio reception is universally poor in summer and good in winter. Generally speaking, reception should be better in the winter months on account of the shortened days and decreased daylight. On the other hand, the sunspots and radio curves show that the increased solar activity actually gave much poorer reception in the winter months of both 1926 and 1927 than during the summers of the same years. With the recent decrease in spots on the sun, radio reception during the last two months of 1928 has shown considerable improvement. It may be mentioned that the high degree of static due to thunder storms in the summer months results in the fact that the average radio listener will decrease the sensitivity of his set in summer to lesson these disturbances with the necessary accompaniment of low audible intensity of distant stations. Hence the general impression of a low intensity accompanying warm weather.

While it has been evident that increasing sunspot activity has been accompanied in general with a decrease in intensity of radio signal strengths received, exceptions occur from time to time due, in part, to atmospheric and possible meterological changes. It has furthermore been possible to obtain a degree of correlation between barometric gradients and the intensity of reception received. It is by taking moving averages of several days data that the sunspot intensity correlation becomes markedly apparent.

A study of the graphs further shows that a rather definite fifteen month period in solar activity exists as exhibited by both spots and radio reception. This is one of the outstanding results of the investigation to date. Each of these sunspot sub-maxima have indicated increasing solar activity and it does not yet appear possible to state that we have reached the real maximum of the sunspot cycle until the sun peak of 1929 is reached and passed. The intensity of that peak will doubtless decide whether or not the maximum of the present sunspot cycle is reached in 1928 or 1929. Contrary to previous announcements it may definitely be asserted that the maximum was not reached in 1927.

Some progress has been made in the correlation of temperature changes with radio reception and while concomitant variation markedly exists it is doubtful if the relation is one of cause and effect. It seems far more plausible that changes in solar activity are more directly responsible for variations in the signal strengths received than that such should be dependent upon any absolute value in atmosphere temperature.

In view of the fifteen months period of maxima and minima which appears to be definitely located both in the sunspot and radio curve, we may look for another maximum of solar activity in September or October 1929