Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

180 FREQUENCY MODULATION, Volume IFi = (60 I/r) sin (u>t) sin (t) cos () (2)The sum of Equation (1) and Equation (2) gives the total resultantfieldF(4,)=F 1+F 2= (60 I/r) [sin (cat) sin () + cos (o>t) cos (changes, giving a circularly symmetrical horizontalpattern.The concentration of energy in the vertical plane is obtained bystacking a number of elemental turnstile units along the vertical axis.The vertical radiation pattern of n units spaced a half-wave lengthapart and cophased is equal towhere F (6) = vertical radiation patternsin [ (nir/2) sin 0]F(6)= (4)wsin [(tt/2) sin 0]n = number of layers6 = elevation angle measured with respect to the horizontalplane.Equation (4) shows that maximum radiation occurs for — 0, or inthe horizontal plane.Radiator Elements and Feed LinesThe radiator elements for the new turnstile design were constructedfrom copper tubing having a two-inch diameter. One of these elementsis shown in Figure 2(a) in its proper position with respect to thesupporting pole. Since the radiator is made slightly less than onequarterwave in length, the impedance measured between the end adjacentto the pole and the pole consists of a resistance component and acapacitive component, as shown in the lower section of Figure 2(a).