The EC81 is a UHF oscillator triode designed for frequencies up to 750 MHz.
The electrodes occupy a small space in the envelope. The anode is blackened to assist cooling. The power output from this special purpose triode is 2.1 Watts.
A close-up of the side of the anode with the cathode and grid within. The anode is 10 x 5 mm when seen at this angle.
The B9A base pins are gold plated for special quality valves.
The external pins are 6.25 mm long. Passing through the hard glass base is the red part of the pin.
At the top of the envelope and fixed to the anode support is the getter holder. The getter would have been fired by RF heating just before the pumping was complete.
The thin glass tube envelope is 20 mm in diameter, and excluding the B9A base pins is 48 mm tall.
References: Data-sheet, 3002. Type EC81 was first introduced in 1950. See also1950 adverts.
