The E1148 was the prototype for the CV6. Commercially the CV6 is known as the DET20, the two are similar but not identical. The valve was developed as a VHF oscillator and bringing the control grid to a top cap as well as the anode enabled the frequency of operation to be high.
This American made valve shows that the E1148 was a production valve as well as an experimental prototype. The base valve that was developed into this high frequency valve was the 6J5 triode.
The horizontal electrodes are held in place by four supports fixed into the glass of the pinch.
At this angle the heater can be seen to pass through the cathode as a single strand.
The grid extends slightly either side of the anode.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 72 mm tall.