. The Bell System technical journal . rable length is necessary to distributethe heat. A coaxial load is preferably tapered from outer conductor to inner con-ductor, since this both reduces the voltage gradient and facilitates heatdissipation. A dielectric consisting of a mixture of bakelite, silica andgraphite, molded in place, has been found satisfactory. For wave guides aceramic containing carbon may be preformed, with taper in one or twodimensions, and cemented in place. Figure 22 shows a number of RF loads developed for different frequencybands. One of these, TS-235/UP, provides an excell
. The Bell System technical journal . rable length is necessary to distributethe heat. A coaxial load is preferably tapered from outer conductor to inner con-ductor, since this both reduces the voltage gradient and facilitates heatdissipation. A dielectric consisting of a mixture of bakelite, silica andgraphite, molded in place, has been found satisfactory. For wave guides aceramic containing carbon may be preformed, with taper in one or twodimensions, and cemented in place. Figure 22 shows a number of RF loads developed for different frequencybands. One of these, TS-235/UP, provides an excellent impedance matchover the frequency range from 500 mc to above 3,000 mc. When equippedwith a blower designed for uniform transverse ventilation, it will handle apeak power of the order of 750 kw with a duty cycle of about .001. Microwave Attenuators and Pads RF attenuators and pads are cornerstones of microwave testing. At-tenuators are used to adjust unknown signals to levels suitable for measure- 474 BELL SYSTEM TECHNICAL JOURNAL. Fig. 22—RF loads for different bands in the microwave frequency range.
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