. The Bell System technical journal . na It was long recognized that an important direction of Radar develop-ment lay towards shorter waves. This is particularly true for firecontrol antennas where narrow, easily controlled beams rather than greatranges are needed. The Polyrod antenna had pretty thoroughly demon- 302 BELL SYSTEM TECHNICAL JOURNAL strated the value of rapid scanning, yet the problem of producing a rapidscanning higher frequency antenna of nearly equal-dimensions was a newand different one. Several possible solutions to this problem were known. The arraytechnique applied so effe
. The Bell System technical journal . na It was long recognized that an important direction of Radar develop-ment lay towards shorter waves. This is particularly true for firecontrol antennas where narrow, easily controlled beams rather than greatranges are needed. The Polyrod antenna had pretty thoroughly demon- 302 BELL SYSTEM TECHNICAL JOURNAL strated the value of rapid scanning, yet the problem of producing a rapidscanning higher frequency antenna of nearly equal-dimensions was a newand different one. Several possible solutions to this problem were known. The arraytechnique applied so effectively to the polyrod antenna could have beenapplied here also, but only at the expense of many more elements andgreater complexity. After much preliminary work it was finally concluded that a mechanicallyscanning antenna, the rocking horse, provided the best solution to thehigher frequency scanning problem. This solution is practical and relativelysimple. - DELAY EQUALIZINGWAVE GUIDE LENGTHS UNIT ANTENNAS(VERTICAL POLYROD TRIDENTS). WAVE GUIDE DISTRIBUTING MANIFOLDWITH ROTARY PHASE CHANGERS(720° PHASE CHANGE PER REV.) INPUT Fig. 52.—Schematic Diagram of Poljrod Fire Control Antenna. The operation of the rocking horse is described in Sec. It is essen-tially a carefully designed and firmly built paraboloidal antenna whichoscillates rapidly through the scanning sector. Its oscillation is dynamicallybalanced to eliminate undesirable vibration. Figure 54 is a photograph of a production model of the rocking horseantenna. The Mark 19 Radar Aiilcmia^^ In Anti-aircraft Fire Control Radar Systems for Heavy Machine Gunsit is necessary to em])loy a highly directive antenna and to obtain continu-ous rapid comparison of the received signals on a number of beam positions Sections , and were written by F. E. Nimmcke. RADAR ANTENNAS 303
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