KSFO was the CBS network affiliate in San Francisco for many years, including the start of WW II.
John Schneider's history of KTAB/KSFO and his separate KQW/KCBS history (with my insertions in parens) outlines how KSFO and CBS became intertwined... divorced and reconciled:
Schneider writes:
http://www.bayarearadio.org/schneider/ksfo.shtml
"Within a matter of two years, the old KTAB had completely transformed itself. But Dumm and Lasky were not satisfied. They contacted Guy Earl and Naylor Rogers, who operated the well-known independent station KNX in Hollywood. Together, they formed the Western Network, a two-station hookup which began operation in 1935. The network functioned successfully until 1937, when CBS bought KNX. In negotiations that followed, KSFO became the Northern California key outlet for the new CBS network, replacing KFRC, and CBS was given an option to purchase KSFO.
Under the direction of CBS, a new quarter-million dollar studio complex was constructed in the fall of 1937 as an annex to the Palace Hotel, boasting no less than seven studios and 26 offices. KSFO took over the new facility the following year, and began construction of a new 5,000 watt transmitter plant at Islais Creek, on the Bay Shore in San Francisco; also, the station's city of license was officially changed to San Francisco.
From 1937 to 1942, KSFO was the origination point for many CBS programs that were heard along the Pacific Coast, and a few heard nationwide. The four-year rise of KSFO from the cellar of the market to the regional key station for CBS became a local broadcast legend."
KQW, San Jose was an also-ran, as John Schneider notes in his history of KQW (with my insertions in parens):
http://www.bayarearadio.org/schneider/kqw.shtml
"But the fate of the station (KQW) changed in 1942. That year, CBS offered to purchase KSFO, its San Francisco affiliate, but the offer was rejected by KSFO's owners. Immediately thereafter, CBS approached KQW with an offer of affiliation, which was accepted. KSFO had occupied a lavish studio complex in the Palace Hotel, which was owned by CBS; KSFO was evicted, and KQW moved in."
"In 1941, when KSFO was still the CBS affiliate in the area, the network had entered into an agreement with KQW which called for KSFO to take over KQW's frequency and increase its power to 50,000 watts. KQW, which was by then operating at 5,000 watts on the frequency, was to move to KSFO's dial position.
The entire transaction was awaiting approval by the F.C.C. when a wartime freeze was placed on all station changes. By the end of the war, however, the CBS affiliation belonged to KQW, and CBS was not about to give up its plans for a 50,000 watt affiliate in the Bay Area. It filed a competing application for a power increase at 740.
After lengthy hearings, the F.C.C. granted the power increase to the original applicant, KSFO. However, the management of KSFO began to have doubts about the future of AM radio, and were putting all of their money into their new television station, KPIX (Channel 5). Negotiations were re-opened with CBS, and the result was that KSFO gave up its claim for the 740 dial position, in exchange for the CBS-TV network affiliation for San Francisco.
In 1949, CBS purchased the license of KQW outright
(from Ralph Brunton and Charles L. McCarthy. Brunton was one of the owners of KJBS in San Francisco, and McCarthy was the Manager of Station Relations for NBC in San Francisco.) and changed the call letters to KCBS. An elaborate multi-tower antenna site was constructed at Novato in Marin County. The new high-power network-owned facility went on the air in 1951."