lower gains. Feeder amplifiers usually operate in the gain range of 26-32 dB with output levels in the range of +47 dBmV. Trunk amplifiers have gains of 21-23 dB, with output levels in the range of +32 dBmV. If we wish to extend the length of the trunk plant, we should turn to using lower loss cable. Using fiber optics in the trunk plant is even a better alternative (see Section 17.4). The gains and levels of feeder systems are purposefully higher. This is the part of the system serving customers through taps. These taps are passive and draw power. Running the feeder system at higher levels improves tap efficiency. Because feeder amplifiers run at higher gain and with higher levels, the number of these amplifiers in cascade must be severely limited to meet CTB and cross-modulation requirements at the end-user. 17.3.7 The Underlying Coaxial Cable System The coaxial cable employed in the CATV plant has a nominal characteristic impedance (Zo) of 75 S. A typical response curve for such cable (7/8-in., air dielectric) is illustrated in Figure 17.5. The frequency response of coaxial cable is called tilt in the CATV industry. This, of course, refers to its exponential increase in loss as frequency increases. For 0.5-in. cable, the loss per 100 ft at 50 MHz is 0.52 dB; for 550 MHz, 1.85 dB. Such cable systems require equalization. The objective is to have a comparatively "flat" frequency response across the entire system. An equalizer is a network that presents a mirror image of the frequency response curve, introducing more loss at the lower frequencies and less loss at the higher frequencies. These equalizers are often incorporated with an amplifier. Equalizers are usually specified for a certain length of coaxial cable, where length is measured in dB at the highest frequency of interest. Grant (Ref. 1) describes a 13-dB equalizer for a 300-MHz system, which is a corrective unit for a length of coaxial cable having 13-dB loss at 300 MHz. This would be equivalent to approximately 1000 ft of COMMUNITY ANTENNA TELEVISION 