American relatives of Soviet dissident Andrei D. Sakharov yesterday said they recently received a postcard from his wife, Yelena Bonner, that they believe to be the first authentic message received from her in the West since her exile to the Soviet interior in April.

"The postcard does not mention Dr. Sakharov at all, and the feeling is that he is not with her," Bonner's daughter and son-in-law, Tatiana and Efrem Yankelevich, said yesterday.

The postcard is dated Aug. 7, but Bonner's daughter said they believe it could not have been written before Aug. 25 because it describes autumn weather and refers to the U.S. visit of a mutual friend.

Because of the difficulty pinpointing the date the postcard was written, "it is hard to tell whether it disproves a claim made by Victor Louis, a Soviet journalist, that the Sakharovs were reunited around Sept. 10," the statement said.

Last month, Louis, a conduit for Soviet intelligence information and propaganda, reported that Sakharov, a Nobel Peace Prize winner, had left a hospital in the provincial city of Gorki and joined his wife in their apartment there.

Tatiana Yankelevich said the postcard was written "in as abstract an air as possible" and made no mention of Bonner's health -- a subject her daughter said she always mentioned, even if only in passing -- or of a trial or sentencing.

The State Department said in August that it had received information that Bonner had been tried for anti-Soviet activities and sentenced to five years of internal exile, presumably in Gorki.