EXPERIENCE IN TECHNICAL INNOVATION: METHOD OF DIPLEXER DESIGN,

The author describes a design for a common antenna used for two radio transmitters. According to transmission line theory, one antenna may be used for two transmitters simultaneously operating on three different wavelengths by employing a crossed filter-network. The filter-network consists of half-wave and quarter-wave transmission-line elements which present different characteristic impedances for different frequencies. Thus, signals of desired frequencies can pass through the filter-network, and signals of undesirable frequencies are blocked. The length of transmission-line elements can be determined, and a feeder having characteristic impedance W - 600 ohm may be used for connecting the common antenna to the two transmitters. In antenna installation, transmission line elements in return circuits A, B, and C must be perpendicular to the feeder, and their shorted ends should be soldered and have good contact. To reduce the power loss, the transmission-line elements are made with copper conductors of 4-6 mm diameter. The author concludes that the crossed filter network is suitable only for a transmitting power below 25 kw.