Abstract: According to an embodiment of the present invention, a high power RF electric signal transmission system such as a TV broadcast system operating in the range of 100 kW at a UHF band includes one or more high power klystrons whose outputs are combined and fed to the first port of a high power Y-junction three port ferrite circulator, the second port of the circulator feeds the broadcast system radiating antenna system, the third port of the circulator feeds a non-reflecting RF load and means are provided for tuning the circulator to compensate for changes in the temperature of the circulator ferrite material, so that the klystron(s) are isolated from reflections from the antenna system.

Abstract: In an ultra high frequency (UHF), high power broadcast television (TV) antenna system that includes a radiating antenna located at the top of a tower structure many hundreds of feet high, a transmitter at the bottom of the tower and a circular waveguide transmission line between the transmitter and the antenna carried by the tower, an undesired polarization mode that is transverse to the desired polarization mode for which the antenna system is adjusted is excluded at the top of the tower structure at the end of the circular waveguide transmission line so that the undesired polarization mode does not energize the radiating antenna and, in particular, the undesired polarization mode does not energize the antenna and produce a ghost image in a TV receiver after reflecting from the bottom end of the circular waveguide transmission line back up to the antenna and does not add a standing wave in the circular waveguide transmission line.

Abstract: A plurality of different frequency signals f.sub.1, f.sub.2, f.sub.3, . . . fn are combined for transmission in a common transmission line by a series of hybrid circuits each including a through coupler for feeding through frequency signals through the hybrid circuit to the output thereof, an injection coupler for feeding an injected frequency signal to the hybrid output and one or more tuned circuits between the couplers that are tuned to the frequency of the injected frequency signal and connected to the couplers by a stub transmission line of electrical length in terms of wave lengths of the through frequency, so that substantially all power of the through frequency signal and all power of the injected frequency signal flow from the hybrid circuit output to the next hybrid circuit in the series.