 KSAN had a limited audience because most television sets could only receive UHF with a special converter.Only in markets such as Fresno and Bakersfield, which had only UHF channels, was there any real reason to purchase such a converter in the 1950s.Later, in the early 1960s, the Federal Communications Commission (FCC) ruled that all television sets had to have tuners for both VHF and UHF channels.