The DEM2 is a modulator valve. It has a more open grid winding than its sister valve the DET2 transmitting RF valve. The valves can dissipate up to 150 Watts and feature molybdenum anodes to allow for the anode running very hot.
The illustration shows that these were double ended balloon valves. The central balloon allows the glass to be at a lower temperature than a cylindrical envelope. This was important as glass becomes lossy at RF with high temperatures.
The envelope shows the signs of the barium/magnesium/aluminium getter used to complete the evacuation.
The envelope has the identification etched into the glass surface. Although not easy to see the electrodes have a complicated structure including a grid collar. The DEM2 and DET2 were popular and successful transmitting valves.
The balloon envelope is 125 mm in diameter, and excluding the connections is 320 mm tall.
Absolute Maximum Operating Conditions¶
Updated December04, 2014. shape:balloon construction:pinch type:triode age:1920.1930 base: pin: