These Hybrid ICs have similar noise figures of 5.5 dB. Lets take this to be 6 dB. If we use this as a starting point, we would arrive at reasonably good estimates for cascades of Hybrid Amplifiers. Clearly, the noise performance is better if the level of the input signal is higher. However, if a network installs amplifiers so that each amplifier receives an input signal of 55 dB, the Noise of the first amplifier itself will be 48 dB. This clearly shows how the noise performance can be adversely affected, if levels are not correctly maintainerd throughout the network. It is not necessary to install expensive amplifiers to keep noise to a low level. It simply requires proper signal levels.
Lets take a a simpler approach.
Similar to the case of Modulators, the noise performance is reduced by 3 dB for a doubling of the number of Amplifiers. In most actual systems, the cascade will not exceed 12 to 16 Amplifiers. However it is clear that the Amplifiers in such a cable network will not contribute significantly in terms of noise. It is often believed that good noise performance can only be achieved by expensive trunk Amplifiers. The facts are quite different.