WHEN will carry Sir Alexander Cadogan's address on "Problems and Prospects of the United Nations" tonight at 8:30 o'clock, Network officials announced yesterday. The British representative to the Security Council will speak from the New Lecture Hall, under the sponsorship of the U. N. Council.

Following Cadogan's broadcast, the Harvard Radio Workshop will emerge from its winter hibernation to present William Saroyan's "Hello Out There," a study of a rapist awaiting his fate at the bands of a lynch mob.