generated noise is not a significant contributor to the output noise, the output S/N ratio per tube remains constant. If the klystrons are operated in parallel instead of cascade, the same noise level per tube would occur. 4.3.5 KLYSTRON POWER LEVEL The converters will have outputs feeding into a waveguide array as described in the transmitting antenna section. Since the waveguide losses vary directly with the rf power output, this should be considered in determining an optimum power output level. The basis for this analysis is the high power klystron described earlier, using a beam conversion efficiency of 75 percent. For final analysis this efficiency was raised to 84 percent. Dr. Kosmahl at Lewis Research Center has predicted this efficiency as being attainable. Figure 4-46 tabulates the resulting tube parameters for the 84 percent beam efficient klystron versus the 75 percent tube. Waveguide losses versus rf power output per tube are indicated in Figure 4-47 for two waveguide configurations. The first configuration has the full rf output power connected directly to the waveguide system using approximately a one meter length of interconnecting waveguide. In the second configuration, the rf output per tube is divided into six, using the configuration of Figure 4-48. The tube output is divided into two by a power splitter and then subdivided into three parts by using sidewall directional couplers. Losses are estimated 2 based upon a waveguide attenuation of 0.015 dB/meter. Only losses are considered. In estimating the losses for the direct connection of the klystron to the antenna, a one meter length of guide was allowed as a connecting link between the klystron and antenna. Klystron parameters obtained by extrapolation of previous data is tabulated in Figure 4-49. Figures 4-50 and 4-51 give the waveguide losses and net efficiency of the two cases studied: the klystron to antenna direct feed and the klystron to antenna connection being made through a 6/1 power divider. The results of this analysis indicate that to a direct connected waveguide the optimum power per tube is at approximately 36 kilowatts. Below 36 kilowatts the solenoid and filament power dominate over the klystron beam efficiency.
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