DCH11

The DCH11 is a directly heated triode-hexode for controlled mixer stages in battery receivers. Telefunken combines a triode oscillator and hexode converter, triode grid internally connected to hexode grid 3. Nominal filament rating is 1.2 V, 75 mA. The note describes one dry cell, permitting decline to 0.9 V in that service; other sources follow its heater-tolerance provision. All voltages reference the negative filament end. Available sheets date from 1941–1942, not independent proof of introduction.

First hexode point: plate 120 V, screens 60 V, signal grid 0 V, plate current 1 mA, screen current 1.5 mA, conversion transconductance 300 µA/V, internal resistance above 1 MΩ. Second: plate 90 V, screens 50 V, currents 0.75 and 1.1 mA, conversion 280 µA/V. Oscillator-grid current multiplied by 50 kΩ gives the listed −5 and −4 V respectively, not an RMS AC amplitude. The static triode at plate 90 V, grid 0 V has starting transconductance 1 mA/V, distinct from hexode conversion.

For dynamic triode operation with average tuned-circuit quality, supplies 120 and 90 V use a 30 kΩ plate resistor, yielding plate voltages 85 and 65 V and currents 1.2 and 0.85 mA. The note assigns 30 kΩ to medium and long waves; for short waves, 10 kΩ at supply 120 V and no resistor at 90 V. An erratum corrects the short-wave schematic caption: this is the triode plate resistor, not the screen resistor. Two oscillator-supply arrangements are also shown for medium and long waves.

Tables distinguish fixed screens from screens supplied through resistance. The latter specifies 40 kΩ, with a note giving 30 kΩ as the standardised value and mentioning practical shared screen supply for DCH11 and DF11. The 1:100 control range reduces conversion transconductance 300 to 3 µA/V at 120 V, and 280 to 2.8 µA/V at 90 V; grid moves 0 to −10 V or 0 to −8 V as screen voltage rises. The fixed-screen table prints final grid values 5.7 and 5.1 V without minus signs. They are not silently corrected or confused with the other arrangement.

Both sections have plate limits 200 V cold and 150 V operating; screens likewise 200 and 150 V. Maximum dissipations: hexode plate 0.3 W, triode plate 0.5 W, screens 0.3 W. Hexode plate plus screen currents total at most 6 mA; triode plate current 3 mA. Maximum grid-leak resistances are hexode 3 MΩ, triode 50 kΩ. Input/output capacitances: hexode 5/6.7 pF, triode 3.8/3.6 pF; hexode signal grid–plate below 0.004 pF. Curves separately cover current, conversion, screen control and triode behaviour.

The German Y8A diagram shows combined screens, signal grid, filament ends, metal envelope at the negative end and separate plates; triode grid is common with hexode grid 3. The primary drawing does not number contacts; no assumed numbering replaces it. Telefunken dimensions: body diameter 36 mm, base diameter 43 mm, height above contact seating plane 43.5 mm, separate lower projection 15.5 mm, not marked maximum. Weight explicitly is maximum 50 g. Photos include a Telefunken specimen with Tjernelds Radio paper band; this does not establish another manufacturer. Documentation: Telefunken, DCH11, Triode-Hexode für regelbare Mischstufen, sheets 011241, 021241, 030342, 040342, eight technical pages and March 4, 2000 index with erratum.