This Mazda exhibit uses the Mullard Type designation EF184. Our 6F30 exhibit is the same valve Type with a Mazda Type designation. The EF184 is a purpose designed frame-grid high gain VHF pentode. The mutual conductance is 15.6.
The valve could be used as an RF amplifier for 405 line television receivers or band two FM radios. We have no details as to its noise performance.
Through the screen it can be seen that the anode consists of one sheet either side of the central grids.
A section of the image above enlarged. The wide spiral of the suppressor grid contains the close spaced screen grid whose wires run flat across the cathode. The frame-grid control grid is very close to the cathode and wound with many strands of very fine wire under tension of about half the breaking strain of the material. The frame-grid itself cannot be distinguished.
The thin glass tube envelope is 20 mm in diameter and excluding the B9A base pins, is 52 mm long.
References: Data-sheet, 3002 & 1040. Type EF184 was first introduced in 1960.