Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

188 FREQUENCY MODULATION, Volume 1Method of AdjustmentThe main flag pole was laid out horizontally on two wooden supportingstructures so that the pole center was approximately twelvefeet above the ground, as shown in Figure 10. The antenna system wasassembled on the pole. Then the North and South radiators weredisconnected from the feed lines and the series inductance sectionsof the East and West radiators were shorted out directly across thes-v»4|Fig. 9—A practical feed system for six layers or more.small cylindrical insulators at the mouths of the inductance sections.Next, the antenna length and the position of the shorting plug onthe support rod (see Figure 3) were changed on each East and Westradiator until the main feed line was properly terminated in its characteristicimpedance. This condition was observed by means of aprobe voltmeter sliding along a slotted measuring line. The antennalength adjustment was made by sliding very thin-walled sleevesoverthe end of the radiator, while shorting plugs with spring-contactfingers were used to adjust the shunt tuning inductance.