The 5876A is a microwave disc seal triode. The device is physically small, coaxially designed and connections are brought out along the body of the valve so as to better locate the valve within a resonant cavity. The cathode connection is made via a spring clip that fits over the metal body.
The valve is rated for high altitude use and for use as a Class C amplifier and oscillator at up to 3.0 GHz.
The cathode is on the left and emerges as a tube that passes through the grid connection ring. The anode is copper and on the right. The grid emerges from the connection ring as a cage of wires that enter the anode.
The whole valve with evacuation seal on the top right.
This exhibit was donated by Barrie Slater. Many thanks. It was salvaged from an American military signal generator.
The thin metal tube envelope is 6.3 mm in diameter and, excluding the base pins, is 54 mm tall. The grid ring is 20 mm in diameter.
References: Data-sheet & 4038. Type 5876A was first introduced in 1964.