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 âonâ there
is high current but low plate voltage and when âoffâthere is no current and
the voltage is high and the tube spends little time between âonâ and
âoffâ conditions.
The error I made came from the fact that the plate load impedance is
constant and the tubeâs 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 âonâ there
is high current but low plate voltage and when âoffâthere is no current and
the voltage is high and the tube spends little time between âonâ and
âoffâ conditions.
The error I made came from the fact that the plate load impedance is
constant and the tubeâs 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
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