. The Bell System technical journal . GASKET Fig. 10—Polyrod and waveguide feed details. 848 BELL SYSTEM TECHNICAL JOURNAL 5. Construction and Operational Details Figure 10 shows a production model of a polyrod for 3000 megacycles,with means for matching it to a rectangular waveguide.^^ A two-iristransformer is used with a resulting width of 4% between the 1 db standingwave points. The clamping illustrated is designed to maintain a firm gripon the rod despite tendencies of the polystyrene to cold flow. Another type of coupling is indicated in Fig. 11. Here the polyrod isstill fed from a wavegu
. The Bell System technical journal . GASKET Fig. 10—Polyrod and waveguide feed details. 848 BELL SYSTEM TECHNICAL JOURNAL 5. Construction and Operational Details Figure 10 shows a production model of a polyrod for 3000 megacycles,with means for matching it to a rectangular waveguide.^^ A two-iristransformer is used with a resulting width of 4% between the 1 db standingwave points. The clamping illustrated is designed to maintain a firm gripon the rod despite tendencies of the polystyrene to cold flow. Another type of coupling is indicated in Fig. 11. Here the polyrod isstill fed from a waveguide but this is in turn transformed to a coaxial composite can thus be regarded as a coaxial to polyrod coupling. Thecoaxial line taps at point b onto the short-circuited antenna a-b-c at a point POLYSTYRENEROD COAXIALFEED. Fig. 11—Coaxial feed for polyrod. chosen to match the characteristic impedance of the coaxial line. The backend of the waveguide is short circuited by a metal cap a quarter wavelengthbehind the transverse wire antenna. A movable coaxial plunger providestuning. This arrangement has a bandwidth of 1% to the 1 db standingwave points. The frequency response of a polyrod is inherently broad. The directivepattern varies slowly with both phase velocity and amplitude distributionalong the axis. As shown in Figs. 1 and 2, these quantities are slowly vary-ing functions of X over a considerable range of polyrod proportions. At Developed by Mr. D. H. RiiiR. DISTANCE FROM FEED, I, IN WAVELENGTHS ^ H MATERIAL STYRAMIC NOISEGAININ DB / P1 \ HARD RUBBER ^-^ / c 1 I 5 \ ACETATE BUTYRATE 90 4 i i 1 t 1 / *N V \ o k? ^ ^^ ^i -50 -40 -30 -20 -10 0 10 20 30 40 50 DEGREES OFF AXIS Fig. 12—Effect of dielectric loss on polyrod performance. ^V 1 I N
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
