New modulation techniques for increased efficiency in UHF-TV transmitters
The use of electron-beam modulation in klystron amplifiers is an important means of reducing the electrical power consumption of ultra-high-frequency power amplifiers, employed in the transmission of television signals. This paper explores the characteristics of the amplifiers, describes the methods developed for applying video modulation, and gives details of typical power savings which can be expected.
13 – Television Transmitters
Publisher Summary 
This chapter discusses television transmitters. There are two basic types of television transmitter, one using combined and the other separate vision and sound amplification. In the first, modulated vision and sound signals are combined at low level and amplified together by a single amplifier chain. In the second, vision and sound are amplified separately and combined at high level. Combined amplification has the advantage that, as only one amplifier is used; the transmitter is simpler, smaller and less expensive. A modulator introduces precorrections adjusted to be equal and opposite to those encountered in subsequent stages to maintain the transmitter output within close specification limits. By enabling the use of a larger part of the power amplifier's transfer characteristic, transmitter efficiency is increased significantly. The up-converter contains two identical chains. Each comprises a double balanced mixer, an amplifier, a channel filter, and a further amplifier. These convert the outputs of the modulator to the radiated carrier frequencies. The local oscillator signal is generated by a synthesizer or a temperature stabilized crystal oscillator with multiplier and filter. It is split to feed both mixers. In subcarrier systems, the composite baseband signal is generated by a coder that is usually a part of the program input equipment. Provided that the sound channel has adequate deviation and bandwidth, multi-channel/stereo sound has little effect on the design of a transmitter.
Thermally Induced Dynamics of Satellite Solar Panels
Thermally induced structural motions are known to affect the attitude dynamics of low Earth orbiting satellites during eclipse transitions. Motions of e exible appendages such as solar panels lead to rigid body rotations of the entire satellite because the total angular momentum of the system is conserved. These potentially large attitude disturbances may violate pointing accuracy and jitter requirements. One type of thermally induced dynamics exhibited by solar panels is thermal snap. The Upper Atmosphere Research Satellite is a prominent example of a satellite that experiences thermal snap disturbances during eclipse transitions. This paper describes recent studies of thermally induced dynamicsof solarpanels, including an analysisofsatelliteattitudedynamics resulting from thermally induced structural motions and a laboratory investigation of the thermal-structural performance of a satellite solar panel. Analytical and experimental results demonstrate thermal bending deformations with acceleration transients that have characteristic thermal snap disturbance histories in response to rapid changes in heating. The studies show that solar panel thermal snap disturbances are caused by through-the-thickness temperature differences that vary at a nonconstant rate. Finite element analysis correctly predicts the thermal snap phenomenon observed in the solar panel experiments.