DCH22

The Philips Miniwatt DCH22 is a triode-hexode frequency converter for superheterodyne receivers. The triode serves as oscillator and the hexode as mixer; triode grid is internally connected to hexode grid 3. The March 1941 multilingual folder is marked tentative. The directly heated filament is nominally 1.2 V, 100 mA in Philips’s document; secondary 1.25 V, 200 mA figures remain separate. Battery, DC or rectified-AC supply, parallel or series-parallel heating are specified.

With fixed screens, 90 V plate, 50 V screens, oscillator-grid resistance 50 kΩ and current 80 µA: at signal grid 0 V, hexode plate current 0.75 mA, screen current 0.8 mA, conversion transconductance 250 µA/V, internal resistance 1 MΩ. At plate 120 V, screens 60 V, oscillator-grid current 100 µA: respectively 1 mA, 1.2 mA, 280 µA/V, 1.3 MΩ. For 100:1 conversion reduction, signal grid reaches −4 V or −5 V, with final 2.5/2.8 µA/V. Conversion transconductance is distinct from triode transconductance.

Sliding-screen operation is separate: screen feed resistor 50 kΩ, supply 90/120 V, signal grid 0 to −6.5/−8.5 V for the same 100:1 control. Screens rise 50 to 90 V or 60 to 120 V. Oscillator triode: supply 90/120 V, plate resistor 21/43 kΩ, plate current 1.4 mA, grid resistor 50 kΩ, grid currents 80/100 µA. Separate static triode point: plate 60 V, grid 0 V, current 2.1 mA, transconductance 1.3 mA/V, amplification factor 21.

Hexode limits: plate 135 V, plate dissipation 0.3 W, combined screen dissipation 0.3 W, cathode current 6 mA, grid-1 resistance 3 MΩ. Screen limit depends on plate current: 135 V at no more than 0.5 mA, or 70 V at 1.5 mA. Triode: plate 135 V, dissipation 0.5 W, common-grid resistance 50 kΩ. Grid-1 −0.2 V and common-grid −0.4 V are positive-current onset criteria at 0.3 µA, not cutoff. Batteries may initially reach 1.5 V, lower proper-operation threshold 0.9 V; series DC/rectified heating requires 100 mA adjusted current with fluctuations at most ±3%.

Hexode capacitances: input 4.3 pF, output 10.2 pF, plate-grid 1 below 0.04 pF. Triode/common-grid figures: input 8.6 pF, to plate 1.5 pF, to filament reference 6.7 pF, plate-reference 5.4 pF; common-grid coupling to hexode grid 1 and plate below 0.4/0.3 pF. Numerous curves distinguish currents and conversion at 90/120 V, fixed/resistor-fed screens, oscillator drive and distortion in the test circuit. Triode curves are separate. Axis ranges are not additional electrical maxima.

The base is eight-contact Loctal, B8G in archive information. The Philips drawing distinguishes both plates, hexode grid 1, common screens, triode grid/hexode grid 3, filament ends and shielding at the negative reference. No printed pin numbers, so the functional arrangement is retained. Maximum bulb diameter 29 mm, base outer diameter 33 mm, body with base excluding pins/lower key height 60 mm. Lower projection 15 mm stays separate, not added to create overall height. Documentation: Philips Miniwatt, DCH22, tentative multilingual data, 12 March 1941, twelve pages including characteristics and curves.