Sensibly equivalent¶ to:
The VP4 is a variable μ RF pentode that was introduced in 1933 on the B5 base. A year later the B7 base version was introduced. This exhibit has an envelope that is close to tubular.
The gain is controlled by altering the bias on the control grid, normal operation is with the bias ranging from -2 to -22 Volts. In a superhet receiver this variation would be derived from the rectified voltage at the end of the IF chain (AGC). The stronger the signal the greater the rectified voltage and this the more negative the control grid is driven and that in turn reduces the amplification of the VP4 in the IF stage.
The reverse is plain.
The classic envelope is 39 mm in diameter, and excluding the B5 base pins is 105 mm tall.
References: Datasheet & 1043. Type VP4 was first introduced in 1933.
Absolute Maximum Operating Conditions¶
Thanks to Andy Cowley for supplying the above PDF datasheet.
Updated July 30, 2015.