Rca1948FrequencyModu.. - The New Jersey Antique Radio Club

CHARACTERISTICS OF THE PYLON FM ANTENNA*tByRobert F. HoltzEngineering Products Department, RCA Victor Division,Camden, N. J.Summary— The pylon antenna is a stack of slotted cylindrical sections.A description of the physical aspects and performance characteristics isgiven.General DescriptionI TRUCTURALLY, mechanically, and electrically this new antennahas been reduced to strictly functional elements. Each pylonsection, Figure 1, is a metal cylinder approximately 13 ft. highand 19 ins. in diameter.It carries no dipoles, no loops, no appendagesof any kind. The radiator is the cylindrical structure itself. A singletransmission line, running up the inside of the cylinder, along theslot to the mid-point, is the feed line.The cylinder is rolled from a single aluminum sheet, bolted at thetop and bottom to cast rings which give itgreat mechanical strengthand provide means for securing the pylon section to the supportingtower or to additional stacked sections.As many as four, and perhaps more of these basic cylindrical sectionscan be stacked to provide a high-gain antenna of remarkablysimple design. Such an assembly is shown in Figure 2. It should benoted that the bottom section is mounted directly on the building roof,without the use of a supporting tower.Origin op the DesignThe cylindrical pylon antenna Has been undergoing developmentsince early in 1944 at RCA in Camden. The principle of the so-calledslot antenna has been employed in a number of applications whereexisting plane metal surfaces had to be adapted to radiating highfrequencyenergy.When it was recognized that these radiating surfaces could berolledinto a cylinder and used for the radiation of omni-directional,horizontally-polarized waves, steps were taken to explore the furtherpossibilities of such a design. As Figure 3 shows, the pylon antennaDecimal Classification : R326.611 X R630.f Reprinted from FM and Television, Sept. 1946.194