the full cable rf video band width of 55 550 mhz is two based on the performance of the existing modulator the maximum required to carry two banks of 25 channels each would be three using the above method it is noted that as only the quadrature component of the modulation contains the required intelligence added envelope noise in the transmission system or the receiver can be eliminated by means of an amplitude limiter in the receiver intermediate frequency amplifier further the inherent amplitude noise of the product detector and the quadrature locked oscillator used to demodulate the phase modulated carrier to recover the signal intelligence is also rejected by the known performance of such a product detector the carrier component in the transmitted signal is used to lock the demodulating oscillator to the transmitted carrier thereby ensuring that the signal to noise degradation of the system is gradual rather than catastrophic the use of the above phase modulation system with its rejection of the inherent amplitude modulation produced at the desired modulation index maximises the number of channels that can be upconverted via a single modulator with linearity sufficient to avoid the production of intermodulation products which would degrade.