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 box anode sits high in the envelope to minimise the lead lengths to the top caps.
The electrode assembly is held rigid by four struts that are secured in the glass pinch.
The wide glass tube envelope is 29 mm in diameter and, excluding the IO base pins, is 71 mm tall.