11E2 — Beam Power Amplifier

An indirectly heated beam power amplifier designed specifically for pulse amplification, break modulators, and series modulation applications.

Overview

The 11E2 (also designated as 11.E.2) is a specialized beam power amplifier manufactured by the Radio Division of The Edison Swan Electric Company Ltd. (Mazda). Introduced for pulse amplification, this indirectly heated valve is characterized by its high peak voltage capabilities and robust design tailored for modulator service. It features a clear glass bulb, an international octal base, and an external side cap for the anode connection to safely handle high peak voltages.

Construction, Physical Dimensions, and Mounting

The 11E2 is constructed with a clear glass bulb and utilizes an I.O.8. (International Octal 8-pin) base. To facilitate high-voltage operation and prevent internal arcing, the anode is connected to an external American Miniature side cap rather than a base pin.

The physical dimensions and physical characteristics of the valve are as follows:

For proper operation and heat dissipation, the manufacturer specifies that the 11E2 must be mounted in a vertical position.

Heater and Pin Connections

The valve features an indirectly heated cathode. The heater is designed for AC or DC operation with the following nominal ratings:

• Heater Voltage ($V_h$): 6.3 V
• Heater Current ($I_h$): 0.9 A
• Calculated Heater Power: 5.67 W (calculated as $6.3\text{ V} \times 0.9\text{ A}$)

Pinout Configuration

The base connections, viewed from the free end of the pins (underside view), are arranged as follows:

The physical orientation of the side cap is indicated on the base diagram as being positioned on the side adjacent to the blank pins and heater connections (specifically aligned near the pin 6/7 region).

Electrical Characteristics and Ratings

The 11E2 is rated for demanding pulse applications, featuring a very high peak anode voltage limit alongside modest continuous dissipation ratings.

Absolute Maximum Ratings

• Maximum Peak Anode Voltage (Pulse Rating) ($V_{a(pk)max}$): 12,500 V
• Maximum Screen Voltage ($V_{[g2](/tubes/G2)(max)}$): 550 V
• Maximum Peak Anode Current ($I_{a(pk)max}$): 1.0 A
• Maximum Anode Dissipation ($W_{a(max)}$): 5.0 W
• Maximum Screen Dissipation ($W_{[g2](/tubes/G2)(max)}$): 1.0 W
• Maximum Potential Heater/Cathode ($V_{h-k(max)}$): 150 V DC

Inner Amplification Factor (Inner Mu)

The inner amplification factor ($\mu_{g1, [g2](/tubes/G2)}$) represents the triode-connected amplification factor of the control grid relative to the screen grid. For the 11E2, this is:

• Inner Mu ($\mu_{g1, [g2](/tubes/G2)}$): 9.0

This value is specifically measured under the following operating conditions:

• Anode Voltage ($V_a$): 200 V
• Screen Voltage ($V_{[g2](/tubes/G2)}$): 200 V
• Anode Current ($I_a$): 25 mA

Inter-electrode Capacitances

The capacitances are measured with the remaining earthy potential electrodes and the heater joined to the cathode (denoted as "Earth"):

• Anode to Earth ($C_{a,\text{all}}$): 7.5 pF ($\mu\mu\text{F}$)
• Anode to Control Grid ($C_{a,g1}$): 0.2 pF ($\mu\mu\text{F}$)
• Control Grid to Earth ($C_{g1,\text{all}}$): 15.5 pF ($\mu\mu\text{F}$)

Applications and Operating Context

The 11E2 is primarily intended for use in break modulators, where its high peak anode voltage rating of 12,500 V and peak current capability of 1.0 A can be fully utilized in pulsed conditions.

Additionally, the valve can be employed in series modulation circuits. In such configurations, it is rated to operate with a standoff voltage of up to 3,000 volts.

Because the continuous anode dissipation is limited to 5.0 watts and screen dissipation to 1.0 watt, the tube is not designed for high-power continuous-wave (CW) RF or heavy continuous Class A audio output service. Instead, its design is optimized for high-voltage, low-duty-cycle pulse applications where the average power remains within the specified limits while handling high peak voltages and currents.

Technical Summary

The 11E2 is a specialized, indirectly heated beam power amplifier designed by the Radio Division of The Edison Swan Electric Company Ltd. for pulse amplification and modulator service. Operating with a standard 6.3 V, 0.9 A heater, the tube is housed in a clear glass envelope with an I.O.8. octal base and an American Miniature top/side cap for the anode. It is capable of handling an exceptional peak pulse anode voltage of up to 12,500 V and a peak anode current of 1.0 A, while maintaining a low continuous anode dissipation rating of 5.0 W. With an inner mu of 9.0 and suitability for break modulators and series modulation (up to 3,000 V standoff), the 11E2 represents a highly focused solution for mid-century radar and pulse-modulation circuitry.