Abstract: An HDTV broadcast transmission system and an analog NTSC broadcast transmission system are carried on the same tower and broadcast to the same area by adaptation of both systems: the NTSC system including: (a) a source of analog NTSC video signals, (b) an NTSC analog video signal exciter producing NTSC IF modulated analog video signals, (c) an NTSC frequency up converter and power amplifier producing NTSC RF modulated analog video signals (NTSC RF signals), (d) an NTSC broadcast antenna and (e) an all band VHF and UHF signal transmission line having an input end and an output end; the HDTV system including: (1) a source of digital video signals, (2) a digital video signal encoder producing IF modulated digital video signals and (3) a frequency up converter and power amplifier producing RF modulated digital video signals (HDTV RF signals) and an HDTV broadcast antenna; by combining the HDTV RF signals and NTSC RF signals at the input end of the transmission line and separating them at the output end and feedin

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: A high power, high frequency, Y-junction three port circulator containing at least one metal plate in the Y-junction covered with ferromagnetic material and an external magnet producing a magnetic field through the ferromagnetic material so that it is magnetized to saturation magnetization when the temperature of the material is within a predetermined temperature range; and a method and means of maintaining the temperature of the ferrite material within said predetermined range even while the circulator operates in a variable ambient environment at high power, including means connected to the metal plate for heating and cooling the plate, thereby controlling the temperature of the ferromagnetic material to maintain the temperature thereof within said predetermined temperature range.

Abstract: In a point to point microwave communication service including a microwave antenna system at each point directed at the other point, the radiation pattern of the antenna system at at least one point has a substantial null in the direction of an antenna of another microwave communication service to avoid an exchange of signals with the other service, the antenna system provided at said one point includes two antenna elements having substantially equal directional radiation patterns, so oriented and spaced apart a distance that is at least several wave length of the operating frequency of the elements so that the radiation patterns of the elements overlap producing a net radiation pattern that results from interference of the patterns and the net pattern has a substantial lobe in the direction of the other point of said service and a substantial null in the direction of an antenna of the other microwave communication service.

Abstract: A high power TV antenna for operation at the ultra high frequency (UHF) frequency F includes a radiating antenna located at the top of a tower structure (often hundreds of feet high), a transmitter at the bottom of the tower and a main circular waveguide transmission line of diameter D1 between the transmitter and the antenna carried by the tower; the feed to and/or from the transmission line including transition sections such that wave propagation in the transition sections is below cutoff for the TM01 mode while it is above cutoff for the dominant TE11 mode while wave propagation in the main circular waveguide transmission line of diameter D1 is substantially totally in the dominent TE11 mode even while it is above cutoff for the TM01 mode, whereby the transition sections tend to inhibit wave propagation in the system in the undesired TM01 mode.

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.