"Is Anyone Out There?"
Frank Drake says in his book:
"Other Soviet scientists ventured out of the range of radio wavelengths altogether, opting to look for pulses of visible light. One of the project scientists still pursuing this optical search is Gregory Beskin, who devotes his spare time to directing and acting in Russian productions of Shakespearean plays. Beskin claims that the Bard himself inspired the optical search with this classic line from Romeo and Juliet: "But, soft! What light through yonder window breaks? It is the east, and Juliet is the sun!" Americans have never favored optical searches, however, because it takes one million times as much energy to communicate at optical wavelengths as compared to radio wavelengths."
In a Soviet Microwave SETI footnote Frank Drake also writes:
"There is a flaw in the Soviet hypothesis, pointed out long ago by Barney Oliver. When the aliens' short (microwave) pulses encounter electrons in interstellar gas clouds in space, they will be slowed down. Electrons slow the speed of light (or any electromagnetic radiation), but not uniformly so. They slow the lower frequencies more than the high ones. As a result, a radio pulse will arrive at different times on different frequencies, making it much harder to detect."
Frank Drake & Dava Sobel, "Is Anyone Out There?", Delacorte Press, 1992, p. 108.