So, moving along from the topic of screen grid voltage regulation
and direction of current flow, here is my other/next question...
Suppose you have a 4CX1500B sitting in the middle of a half wave
plate strip line for 144 MHz. Some may prefer to think of it has two
quarter wave lines with the tube between them. This is a "teflon
sandwich" line where the upper brass plate is connected to the tube
anode, the lower is not. The lower brass plates are grounded at the
far end from the tube. Between the upper and lower plates we have a
thin sheet of teflon that forms the dielectric for the DC blocking
capacitor.
Can someone help me understand whether (and if so why) there would
be significant RF voltage across the blocking cap? Obviously RF
voltage is going to vary along the *length* of the line, being high
at the tube and near zero as we get toward the grounded end. But
what about voltage across the teflon sheet between the upper and
lower plate *at any given point along the line*?
I am trying to understand WHY this thing would want to arc or break
down only when RF is present. My mind wants to believe that the RF
voltage across the capacitor at the point where the teflon shoulder
washers insulate the screws holding it together would not be
significant, and that the voltage would be just B+ regardless of
whether RF is present or not. However I see evidence this is not the
case and want to know what it is that I don't understand.
73,
Paul N1BUG
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