18GE6 — High-Mu Triode Double Diode

The 18GE6 is a miniature, high-mu triode double diode vacuum tube designed primarily for detector-amplifier applications in AC/DC radio receivers. It features a coated unipotential cathode and is housed in a small T-5½ glass envelope with a 7-pin miniature button base (7BT). The tube is designed to operate with an 18-volt heater supply, making it suitable for series-string heater arrangements.

Physical Construction and Base Configuration

The 18GE6 is constructed in a miniature T-5½ glass bulb. It has a maximum overall length of 2 ⅛ inches, a maximum seated or bulb length of 1 ⅞ inches, and a maximum diameter of ¾ inch. The tube can be mounted in any position.

The electrical connections are made through a miniature button 7-pin base (7BT). There are two documented pinout configurations for this base, which differ in the assignment of the cathode and the first diode plate:

Pinout Configuration A

Pinout Configuration B

In both configurations, the heater pins (3 and 4), the triode grid (pin 1), the second diode plate (pin 5), and the triode plate (pin 7) remain identical.

Heater Ratings

The heater is designed for series-string or direct-voltage operation with the following ratings:

Direct Interelectrode Capacitances

The direct interelectrode capacitances of the 18GE6 are measured without an external shield. The typical values are:

Maximum Ratings (Design-Maximum System)

The limiting values for the 18GE6 are established under the Design-Maximum System. Operating the tube beyond these limits may impair its performance or lifetime.

Typical Operating Conditions and Electrical Characteristics

Under typical Class A1 amplifier operating conditions, the triode section of the 18GE6 exhibits a high amplification factor of 70, making it highly effective for voltage amplification.

Triode Section (Class A1 Amplifier)

Diode Sections

The two diode sections are intended for detection and automatic volume control (AVC) or automatic gain control (AGC) functions. Under a specific test condition, the average diode current is characterized as follows:

• Average Diode Current (Each Diode): 2.0 mA (measured with 10 V DC applied; this is a test condition only and does not represent a continuous operating rating).

Intended Applications

The 18GE6 is specifically designed for detector-amplifier applications in AC/DC type radio receivers. The combination of a high-mu triode and two independent diodes in a single miniature envelope allows the tube to perform multiple functions simultaneously. The diode sections are typically used for AM signal detection and generating automatic volume control (AVC) bias, while the high-mu triode section provides the subsequent audio-frequency voltage amplification. The 18-volt, 100 mA heater rating is optimized for integration into series-connected heater strings of compact line-powered receivers.

Technical Summary

The 18GE6 is a miniature, high-mu triode double diode featuring a coated unipotential cathode, housed in a T-5½ glass envelope with a 7-pin miniature button base. Operating with an 18 V, 0.10 A heater, it is designed for series-string AC/DC radio receivers. The triode section provides an amplification factor of 70, a transconductance of 1,700 μmhos, and a plate resistance of 40,000 Ω at a typical plate voltage of 100 V. The two independent diode plates are rated for a maximum continuous current of 1.0 mA each, with a test-point current of 2.0 mA at 10 V DC. With a maximum plate voltage rating of 150 V and a plate dissipation limit of 0.5 W, the 18GE6 serves as a compact and efficient detector-amplifier solution.