POWER AMPLIFIER FOR MODULATED WAVES 475 



spectrum, where the effect is most pronounced because of the smaller 

 band width. 



The power required by this transmitter, including all auxiliary 

 equipment, was 135 kilowatts with normal program modulation, as 

 compared with approximately 230 kilowatts required in the usual 50- 

 kilowatt installation. 



High-efficiency operation, in addition to affording a large saving 

 in the plate power supply, reduces the plate dissipation by a factor 

 of three or four, with a resulting economy in the cooling system and an 

 improvement in tube life. 



The absence of any such requisites as the complicated driving stages 

 of the Chireix system or the large audio equipment involved in high- 

 level modulation gives the new circuit an important advantage over 

 other high-efficiency systems in cost of apparatus and simplicity of 

 design. The new amplifier, moreover, is operated at a plate voltage 

 consistent with safety to the tubes, and is therefore not subject to the 

 operating difficulties encountered at the high peak plate voltages 

 required in high-level modulation. 



