Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

182 FREQUENCY MODULATION, Volume IThe method of supporting the antenna is shown in Figure 2(b).Here a one-inch tube extends from the support pole out through theradiator, and a metal shorting-plug connects the inner tube to the outersleeve. Thus the impedance of the radiator is shunted by the inductivereactance of the transmission line formed by the inner surface of theouter sleeve and the outer surface of the inner tube.If the shorting plug is placed in the proper place, the entire combinationwill be tuned to parallel resonance and the impedance will bea pure resistance, as shown in the lower part of Figure 2(b). Themagnitude of this pure resistance will be determined by the lengthchosen for the outer sleeve.If R a is the resistance of the outer sleeveand X a is the capacitive reactance of this same sleeve, the parallelresonant resistance is•out