The 6A8GT is a triode heptode frequency changer. The oscillator is required to generate 20 Volts pk-pk.
Below the rim of the bright anode can be seen some of the wire grids.
Although small the valve still has the pinch holding the electrode supports and providing the exit point for the connections.
The top mica show in the construction of the mixer around the central cathode. Grid two, the oscillator anode, is just a pair of rods without a winding. The signal input from the top-cap sits between the pair of screening grids.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 73 mm tall.
Reference: Data-sheet. Type 6A8GT was first introduced in 1937. See also1937 adverts.
