CCH2

The CCH2 combines a triode and heptode for frequency conversion in radio receivers. The Philips Miniwatt collection dated 5 October 1938 explicitly describes the heptode as converter and triode as oscillator. Indirect heating requires 29 V and 0.2 A, with series heaters supplied by AC or DC. The drawing shows the European side-contact base, top connection for heptode grid one, and internal connection between heptode grid three and triode grid. Maximum bulb diameter is 32 mm and height 138 mm. Circuit descriptions and curves explain its operation beyond the simple classification as a mixer valve.

Philips specifies heptode anode 100–200 V, screen grids two and four 100 V, cathode resistor 140 Ω and oscillator grid resistor 50 kΩ. Oscillation on grid three is 8 V RMS, with 200 µA grid current. Without automatic gain control, grid one is −2.5 V: anode current 3.25 mA, combined screen current 6 mA and conversion transconductance 750 µA/V. At −25 V the latter falls to 7 µA/V, described as roughly hundred-to-one regulation; at −34 V it is 2 µA/V, the stated limit of the optimum control range. Initial internal resistance is 1.5 MΩ at 200 V anode and 0.7 MΩ at 100 V, exceeding 10 MΩ at both controlled points. The oscillator triode draws 9.5 mA at 100 V anode under the specified oscillating conditions; 24 mA, 5.5 mA/V and amplification factor 17.5 instead belong to the static point with zero grid voltage and no oscillation.

Philips gives separate limits: heptode anode 300 V and 1 W dissipation, triode 125 V and 1 W, both 550 V cold anode. Heptode screens allow 125 V, 0.6 W combined and 550 V cold. Further limits are 25 mA cathode, 3 MΩ heptode first-grid leak, 20 kΩ external heater–cathode resistance and 100 V heater–cathode DC or AC RMS. Philips also tabulates inter-section capacitive coupling: below 0.06 pF from triode anode to heptode grid one, 0.9 pF between anodes and 0.16 pF between their control grids. Heptode input and output capacitances are 8.4 and 13.8 pF; grid-one–anode capacitance is below 0.015 pF.