[ARC5] 10 meter BC-454 - yet more

[Bill Fuqua]

    Now that is the first time I have see that.
However, it does make some sense.
Ok, if you have a fixed screen voltage it is sharp cut off.
I can accept that. Just like many sharp cut off pentodes and tetrodes.
   It seems in condition 2 they are depending on the screen voltage to
affect the gain of the tube by allowing it to vary with screen current.
    I  understand the remote cut off since as the control grid gets more
negative the screen grid goes more positive thus constantly moving the
cut off voltage more negative.
Hmmm, have to think about this a bit more.

73
Bill wa4lav


At 10:41 PM 2/4/2013 -0800, Ian Wilson wrote:
>The 6AC7, according to the data sheet, is either sharp cutoff or remote
>cutoff depending on how you control the screen grid:
>
>*When a fixed screen voltage is used, as shown in condition 1, a
>sharp-cutoff*
>*characteristic is obtained.*
>*
>*
>*When a screen resistor is used, as shown in condition 2, an extended cutoff
>*
>*characteristic is obtained which may be utilized in applications where the*
>*gain is controlled by variation of the grid bias.*
>
>(GE data sheet).
>Condition 1: 150v fixed screen voltage.
>Condition 2: 60k screen resistor to +300v.
>
>73, ian K3IMW
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