[Amps] Screen grid modulation

[Bill L. Fuqua]

     Just got home and turned on the computer. See lots of emails and have not gotten around to looking at them yet. But it occurred to me this morning that I had made an error. 
    The screen grid modulated tube at reduced plate voltage may be operating class C but the plate RF voltage swing is not going to be nearly as low as it will be full screen voltage.   Just like a switching transistor power supply, the higher efficiency comes from the fact that when the tube is “on” there is high current but low plate voltage and when “off”there is no current and the voltage is high and the tube spends little time between “on” and “off” conditions. 
    The error I made came from the fact that the plate load impedance is constant and the tube’s plate impedance changes with the screen voltage.  The tube would operate at high efficiency at maximum output and carrier only power conditions if the output network was always optimized which is impossible to do at an audio frequency rate. 
73
Bill wa4lav
 ten around to looking at them yet. But it occurred to me this morning that I had made an error. 
    The screen grid modulated tube at reduced plate voltage may be operating class C but the plate RF voltage swing is not going to be nearly as low as it will be full screen voltage.   Just like a switching transistor power supply, the higher efficiency comes from the fact that when the tube is “on” there is high current but low plate voltage and when “off”there is no current and the voltage is high and the tube spends little time between “on” and “off” conditions. 
    The error I made came from the fact that the plate load impedance is constant and the tube’s plate impedance changes with the screen voltage.  The tube would operate at high efficiency at maximum output and carrier only power conditions if the output network was always optimized whic