Simultaneous observations of field-intensity measurements of WWV at Needham, Massachusetts, and at Intervale, New Hampshire, during the summer of 1947

A study of continuous field recordings of WWV at Needham, Massachusetts, 373 miles from the transmitter at Beltsville, Maryland, has revealed that the diurnal pattern of reception undergoes a progressive metamorphosis, not only with the seasons, but with the change in sunspot-numbers. This suggests the possibility of predicting fields over a given path based on actual records of performance, provided the records obtained at Needham are representative of a considerable area throughout which such variations may take place. An experimental field station for recording field intensities of WWV, operated during the summer of 1947 at Intervale, New Hampshire, at a distance of 463 miles from Beltsville, has made possible direct comparison with fields obtained at the Cosmic Terrestrial Research Laboratory at Needham over the same interval. Results show the same general form of diurnal variation at the two stations for both the 5-Mc and the 10-Mc frequencies. The logarithm of the ratio of the 5-Mc fields Needham/Intervale ranges from 1.3 at night to 1.7 during the noon hour. Subsequently, the mobile recorder was set up at New Haven, Connecticut, at a distance of 270 miles from Beltsville, and simultaneous recordings were made during the autumn of 1947 with similar results. Sudden ionospheric disturbances and major fadeouts have been observed to occur simultaneously at Intervale and Needham, and at New Haven and Needham. The results of these investigations indicate that the changing patterns observed at Needham must essentially apply to a considerable area approximating at least a hundred-mile radius from the Laboratory at Needham.