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The DET29 was the last in the line of dull emitter triodes from M-OV. The DET29 valve was a specialist microwave co-axial power valve. It would produce 1.5 Watts at 3.8 GHz, and gave useful output up to 5 GHz.

The British Post Office used the DET29 as a line amplifier at 4 GHz for microwave links. Other uses included service as a frequency doubler up to 7 GHz.

An unusual feature in this DET is that the heater connections, flying leads, are separate from the cathode cylinder.

The manufacture of this valve was also special. The cathode tip was made a telescopic fit in the main cathode tube, and during assembly a fine threaded mandrel would be used, within the cathode, to push the tip towards the grid. When the capacitance reached the desired value the tip was then locked into position. Clearly labelling the DET29 as high precision and not high volume.

It can be seen above that the anode comes very close to the mesh grid. On the other side of the mesh grid the cathode is also very close to the grid. Thus the active area of the valve is a tiny portion of the long body.

The disc seal (glass) envelope is 9 mm in diameter and, excluding the flying leads is 65 mm tall.

References: Data-sheet & ¹⁰⁴⁰. Type DET29 was first introduced in 1959. See also 1959 adverts.

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.