Science: Reflected Waves

Like light waves, radio frequency energy tends to travel in a straight line. In the lower frequencies, radio waves that shoot skyward bounce back from electrically charged layers of the upper atmosphere, thus clearing the curve of the earth. Most Very High Frequency waves (30 to 300 megacycles) bore right through the upper atmosphere and are dissipated into outer space, so V.H.F. should not travel far beyond the visual horizon.

But as TV antennas sprouted from the nation's rooftops, and radio hams got on the air again after World War II, some curious reports drifted in to puzzle the radio men. No one had thought that V.H.F. was good for much besides short-range contacts, but now & then people were picking up TV programs they had no right to see; pictures from distant cities were flickering across their screens. Hams operating on V.H.F. frequencies were talking across astonishing distances.

At the National Bureau of Standards, Physicist Joseph Feinstein studied the strange reports. Even allowing for some bending of radio waves in the dense lower atmosphere, conventional theory could not explain what was happening. Feinstein knew that just as there is some light reflected back when light waves pass from air through glass, a small amount of V.H.F. energy is reflected when V.H.F. waves cut upward through the thinning atmosphere. Perhaps, he reasoned, if minute amounts of this energy are reflected in such a way that they reinforce each other, weak but detectable signals will be heard at unexpected distances.

As the reports piled up, more & more scientists agreed. Hams, who have seen this sort of thing happen before, realized that the "useless" radio bands might soon be so valuable that their slice would be drastically trimmed. By last week Bureau of Standards scientists, who are now sure that V.H.F. reflections are no freakish accidents, were more convinced than ever that V.H.F. will provide a vast new frontier for commercial broadcasts.