The ARP in the ARP26 indicates a UK Army receiving pentode. This valve was renamed CV1340 when the Common Valve register was introduced in 1941. The prototype was the M-OV KT44 Beam tetrode.
The open end of the anode reveals the two wire grids and the bright beam plates.
The main heat is generated in the centre of the anode and this is where the heat sinking flanges are located. Note the ceramic insulators.
A closer view. The control grid is wound on copper supports. The grids are aligned and pass flat across the cathode.
The grid wires are secured in the supports by normal the notch and peen method.
The classic envelope is 56 mm in diameter, and excluding the B7 base pins is 131 mm tall.
