The 6883B is the 12.6 Volt version of the 6146B small HF transmitting beam tetrode valve normally used in pairs as the final linear PA stage within transmitters of 100 W output at frequencies up to 30 MHz and transmitting CW or SSB.
The 6883B is also rated for use as an oscillator and a modulator. In the latter role a pair operating in class B would feed the modulation transformer of a high level modulated AM transmitter.
The valve ia also interchangeable with the 8032A and 8552.
The bridge plate connecting to the anode at two points and the control grid cooling fin.
The wide glass tube envelope is 38 mm in diameter and excluding the IO base pins, the valve is 81 mm.
Reference: Datasheet. Type 6883B was first introduced in 1964.