Charles L. Seeger, a pioneer radio astronomer who began tinkering with his own crystal sets by the age of 10 and conceived the forerunner of a great European radio observatory nearly 50 years later, died of congestive heart failure at his Palo Alto home on Aug. 26. He was 89.

Professor Seeger had long been fascinated by the prospect of detecting radio signals from intelligent beings in distant reaches of the galaxy, and nearly 30 years ago he joined NASA's SETI (search for extraterrestrial intelligence) project at the Ames Research Center in Mountain View while on the astronomy faculty at San Francisco State University.

When the Space Agency curtailed funds for the project, however, he joined the nearby nonprofit SETI Institute, where he continued working for the rest of his career.

Besides his highly technical engineering skills, Professor Seeger had a lively imagination and an infectious sense of humor. During a television debate about the merits of various scientific disciplines, he advised Melvin Calvin, the Nobel laureate biological chemist: "The trouble with you biologists is that you're always tinkering with nature, while we astronomers only want to observe it and leave it alone!"

Professor Seeger was born in Berkeley, where his father, the late Charles Seeger Jr., headed the first music department on the University of California campus.

The famed musician Pete Seeger, younger brother of the astronomer, recently recalled his youthful wonder that Charles, even as a child, "was able to build a crystal set and listen with earphones to music which came from far away without needing wires like a telephone."

After high school, Charles Seeger worked at radio stations and other radio industry jobs before earning an engineering degree from Cornell at the age of 34. He immediately joined the Cornell faculty as an assistant professor and played a key role in creating the Cornell Radio Observatory, the first such facility at a university.

It led to the creation of Cornell's famed Arecibo telescope in Puerto Rico, the world's largest radio antenna, among whose many scientific functions now is to scan among millions of frequencies that might contain signals from extraterrestrial intelligences.

In 1950, Professor Seeger began a 12-year sojourn in Europe, principally at the Leiden University Observatory in the Netherlands, where he conceived an array of radio telescopes called the "Benelux Cross" and designed to be financed by Belgium, Holland and Luxembourg.

Because of finances and politics, however, the cross was never built. Instead, the idea led to construction of the Westerbork Telescope, a Dutch lineup of 14 25-meter dish-shaped antennae where Professor Seeger worked and which still functions as a major radio observatory.

While at Leiden, Professor Seeger built many of the stable and sensitive receivers that have been necessary for mapping cosmic objects in interstellar space, and discovered the polarization of radio noise from the Milky Way.

After his work in Europe, Professor Seeger continued his career at Stanford,

Berkeley and San Francisco State, and also held academic appointments at universities in Texas and New Mexico.

Professor Seeger is survived by his wife, Naomi; sons Jeremy, Matthew and Nicholas; daughters Cassandra Underwood and Barbara Seeger; stepdaughter Heather Weihl; brothers John, Peter and Michael; sisters Barbara Perfect and Peggy; and nine grandchildren.

Services will be private. Memorial contributions may be made to the SETI Institute, 2035 Landings Drive, Mountain View, CA 94043.