Fig. 1 shows, as part of the proposed installation at Goldstone, a transmitting module consisting of one square metre of slotted waveguide and a magnetron directional amplifier consisting of two microwave oven magnetrons and a passive microwave device called the ‘magic T'. This arrangement eliminated the need for a high-power ferrite circulator that would otherwise have been necessary and which has become a general feature of the SPS transmitter design using magnetrons. While the proposed test was not funded, the proposal stimulated the Raytheon company to examine the magnetron for the SPS application. The effort led to the discovery of hitherto unrecognized properties in the magnetron of very low noise emissions and a built-in feedback control of cathode temperature to provide very long life. Both these properties are of enormous importance in the SPS system. These findings, when presented to NASA, led to the NASA support of a study effort to examine the potential capability of the magnetron to meet the SPS transmitter requirements [7, 1]. These requirements, show in Table 1, must be met simultaneously, and represent most unusual demands upon a microwave generator or amplifier, particularly in a space environment. The Heat Dissipation and Radiation Problem Getting rid of the heat generated by any inefficiency in the microwave generator itself
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