Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

196 FREQUENCY MODULATION, Volume IA compromise was struck at this stage of the development.Investigationsrevealed that the slot width could be used to control theabsolute value of the impedance level at the feed point.This characteristicwas explored carefully,in order to arrive at an optimum design.Careful tests were carried out to make certain that a round cylinderwould yield the optimum characteristics.It was found that no reasonabledegree of ovality improved the performance in any way.Multipleslotcylinders, with more than one slot on the periphery, were con-^P^ i8\Pig. 3—Each section serves as anumber of circular elements.Fig. 4-—The slot functions as atransmission line when fed withpower.sidered and rejected because the structural and electrical simplicitywere lost.CharacteristicsPylon sections can be stacked to provide higher gain. Figure 2shows a 4-section assembly which has a power gain of 6.As many as8 sections can be stacked in the same manner to give a power gain of 12.Figure 5 illustrates the very simple feeder system required for 1,2, and 4 sections. The lines are actually run inside the pylon sections,