To provide sufficient bandwidth for the chrominance signal, yet interfere only with the highest-frequency (and thus least perceptible) portions of the luminance signal, a chrominance subcarrier near 3.6 MHz was desirable. 227.5 = 455/2 times the line rate was close to the right number, and 455's small factors (5 × 7 × 13) make a divider easy to construct.
to provide sufficient bandwidth for the chrominance signal yet interfere only with the highest-frequency (and thus least perceptible) portions of the luminance signal a chrominance subcarrier near 36 mhz was desirable 2275 = 455/2 times the line rate was close to the right number and 455's small factors (5 × 7 × 13) make a divider easy to construct