Radio Station JUM, Tokyo and
the RCA Station, San Francisco
The RCA commercial shortwace station was headquartered in the RCA Overseas Communications building on the southeast corner of Mission St. and Van Ness Ave., South, in the South-of-Market district of San Francisco. The transmitter was in Marin County.
The station had relayed thousands of important messages during the war, including Army messages between Honolulu and Washington immediately following the attack at Pearl Harbor. It also relayed correspondent reports for NBC and CBS from the Pacific Theater of Operations.
Japan's capitulation was not known to the Japanese people as Gen. MacArthur attempted to contact Tokyo to arrange terms of cessation of hostilites.
On August 15, 1945, dozens of Signal Corps and commercial stations around the world attempted to contact JUM, the Tokyo commercial station that had handled commercial traffic with RCA, San Francisco, before the war.
Those contact attempts were, at first, ignored. However, JUM did pause while transmitting financial data to the Swedish station at Stockholm and acknowledged RCA's contact.
KER DE JUM ZOK GA 40/SWO ZHC 2105 JIT
Translation: "KER from JUM. Receive OK. Go ahead. Send at 40 words per minute. How are receiving conditions? 9:05 p.m. Japan Time.
The operator in San Francisco acknowledged the contact, then JUM transmitted:
KER DE JUM ZSF FIVE
Translation: KER from JUM, send five words per minute faster.
KER transmitted Gen. MacArthur's statement:
I HAVE BEEN DESIGNATED AS THE SUPREME COMMANDER OF THE ALLIED POWERS, THE UNITED STATES, CHINA, THE UNITED KINGDOM AND THE UNION OF SOVIET SOCIALIST REPUBLICS, AND EMPOWERED TO ARRANGE FOR THE CESSATION OF HOSTILITIES TO THE EARLIEST POSSIBLE DATE. IT IS DESIRED THAT A RADIO STATION IN TOKIO BE DESIGNATED FOR CONTINUOUS USE IN HANDLING COMMUNICATIONS BETWEEN THIS HEADQUARTERS AND YOUR HEADQUARTERS.
JUM then acknowledged: KER DE JUM MR MSG BQ NR 76500 RVD OK BT
Translation: KER From JUM. Your message text 76500 received OK. Break.