EL153

The EL153 is a Telefunken transmitting tetrode for short waves and VHF, indirectly heated and radiation cooled. Both manufacturer documents call it a tetrode, although some brief archive entries say pentode. The preliminary bundle calls it a 70 W RF tetrode; that title does not replace actual operating tables or mean anode dissipation, whose stated maximum is 40 W.

The preliminary heater rating is 6.3 V, approximately 1.55 A; pages 563–564 instead give approximately 1.5 A with parallel AC or DC supply. These approximations are not averaged. The latter measurement point uses anode 600 V, screen 250 V, control bias −49 V: anode 50 mA, screen 0.3 mA, transconductance 4 mA/V, internal resistance 20 kΩ. Capacitances are input 14 pF, output 6 pF, grid-anode below 0.35 pF; the preliminary sheet instead gives approximately 14.5 and 5.5 pF and grid-anode at most 0.35 pF.

Page 563 describes a single class-B RF tube below 200 MHz. With screen 250 V and bias −80 V, anode supply increasing from 250 to 500 V gives output 12 to 30 W; both specify anode 130 mA, screen about 2 mA, grid 3.5 mA and RF excitation 100 V. A class-B push-pull pair at anode 625 V, screen 250 V, bias −75 V gives 80 W total, with anode current 125 mA per tube, not 80 W per tube.

The preliminary bundle gives further near-class-B points: wavelength 3 m, anode 650 V, screen 210 V gives about 50 W RF with about 4 W drive; at 1.7 m and anode 500 V output becomes about 30 W with 4.5 W drive. These are total tube RF outputs; antenna power is lower due to circuit losses. Curve families at screen 250 V complement the examples without making the bundle title a universal performance.

Both agree on operating anode 650 V, anode dissipation 40 W, screen 300 V and 5 W, cathode current 230 mA, heater-cathode 200 V. Envelope must stay within 300 °C. Page 564 separately gives cold anode 1000 V, cold screen 800 V. Grid-leak resistance depends on temperature: 250 kΩ below envelope 200 °C, or 25 kΩ below 300 °C; the preliminary sheet gives 25 kΩ. The thermal condition is retained rather than treating 250 kΩ as universal.

The specific ten-position base uses Telefunken socket 30216. Drawings show functions and orientation but no contact numbers; no pinout is borrowed from a similar EL. Preliminary dimensions are diameter 40 mm, height above terminals 87 mm, overall 95.5 mm, not qualified as maxima; the other sheet gives maximum 40 and 87 mm and maximum mass 45 g. Retention against dislodging is required outside vertical mounting. Documentation: Telefunken EL153, Strahlungsgekühlte 70 Watt HF-Tetrode, preliminary data, three pages; Telefunken EL153, Transmitting tetrode for SW and VHF, pages 563–564; photographs of Telefunken specimens and carton.