Figure 4-6. Anode Radiator Diameter versus Frequency In the frequency range of 1.5 to 2. 5 GHz, the radiator diameter is 40-46 cm and the weight varies from 600 to 1000 grams. This was later changed to 48 cm and 1000 grams at 2.45 GHz based on system studies described in Section 6. The large variation in radiator weight is due to larger power generation at the lower frequency. The radiator size is important because it limits the packing density of the tubes near the center of the array. Other tube parameters that vary with frequency such as size, magnetic field intensity, operating current, dissipated power density, and temperature drop across the vanes, are shown in Figures 4-8 through 4-12. Since high efficiency is of prime importance, tubes operating at the lower frequencies are more desirable. However, below 2. 5 GHz the larger tube dimensions increase the specific weight. At the higher frequencies, the magnetic field intensity becomes quite high. Therefore, the information obtained from these figures further shows that 1.5 to 2. 5 GHz is a desirable frequency range.
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