The affiliate map does not show Cleveland. The NBC affiliate there, Cleveland's second TV station at the time, has been on the air since 1948; how could whomever drew this map have missed it?
The only thing I can figure is the station was not yet an NBC affiliate when it first signed on. I don't know when the station officially affiliated with the network, although, since NBC already operated a 50kW radio station in Cleveland in 1951, the television station, which was also operated by the network, would have become an NBC affiliate as well--as soon as or shortly after it began telecasting. The coaxial cable issue, however, may have had something to do with the station's actual affiliation date.