Data set 01
1948 Brimar Radio Valve Manual
Published operating points and test conditions from this source.
SECTION 1
Pentode
Characteristics
Cutoff characteristic
Variable-mu
Voltage Pentode - Remote Cutoff (single) ·Pentode
1A4E
Directly heated variable-mu battery pentode for gain-controlled RF amplification with economical 2 V, 60 mA filament operation.
Directly heatedCold cathodeCommon cathodeDissimilar
- Sections
- 1
- Base
- -
- Socket code
- IO
- Base pins
- -
- Nominal heater
- 2 V / 60 mA
Description
1A4E — Vari-Mu Battery R.F. Pentode
Overview
The 1A4E is a vari-mu (variable-mu) radio frequency (R.F.) pentode designed primarily for R.F. amplification in battery-operated equipment. It features a glass bulb construction with a top cap and is designed for low-power filament operation, making it suitable for portable or battery-powered receiver designs. The tube is classified as an obsolete type and is maintained for reference purposes.
Physical Construction and Base Configuration
The 1A4E is constructed with a glass envelope that incorporates a top cap for the control grid (G1) connection. This physical separation of the control grid from the other electrodes helps minimize input-to-output capacitance, which is beneficial in high-frequency amplification stages.
The physical dimensions of the tube are:
- Maximum Diameter: 1-9/16 inches
- Maximum Height: 3-7/8 inches
The tube utilizes a standard 4-pin U.X. Base. The pinout configuration, viewed from the bottom of the base, is as follows:
| Pin / Terminal | Connection |
|---|---|
| Pin 1 | Filament Positive (F+) |
| Pin 2 | Anode (A) |
| Pin 3 | Screen Grid (G2) |
| Pin 4 | Filament Negative (F-), Suppressor Grid (G3) |
| Top Cap | Control Grid (G1) |
The suppressor grid (G3) is internally tied to the negative side of the filament (Pin 4), simplifying external circuit wiring.
Filament Ratings
The filament is designed for direct heating from a low-voltage battery source. The electrical requirements for the filament are:
- Filament Voltage: 2.0 V
- Filament Current: 0.06 A (60 mA)
- Calculated Filament Power: 0.12 W
The extremely low current draw of 60 mA is optimized to conserve battery life in portable receivers.
Electrical Characteristics and Typical Operating Points
The 1A4E operates as a variable-mu pentode, allowing for automatic volume control (AVC) or manual gain control by varying the control grid bias. Under typical operating conditions, the electrical characteristics of the tube are defined as follows:
| Parameter | Value |
|---|---|
| Anode Voltage | 135 V |
| Screen Grid (G2) Voltage | 67.5 V |
| Control Grid (G1) Voltage | -3.0 V |
| Anode Current | 2.2 mA |
| Screen Grid Current | 0.9 mA |
| Anode Impedance | 1.0 MΩ (megohm) |
| Mutual Conductance (Transconductance) | 0.65 mA/V (650 µmhos) |
At this operating point, the total current drawn by the plate and screen grid combined is 3.1 mA, which, when added to the filament power, represents a highly efficient design for battery-operated R.F. amplifier stages.
Technical Summary
The 1A4E is a specialized vari-mu battery R.F. pentode housed in a glass bulb with a 4-pin U.X. base and a top cap. Operating with a highly efficient 2.0 V, 0.06 A filament, it is optimized for radio frequency amplification in battery-powered equipment. With a typical anode voltage of 135 V and screen voltage of 67.5 V, it provides a mutual conductance of 0.65 mA/V and an anode impedance of 1.0 megohm. The tube is now designated as an obsolete type for reference only.
Socket description
International Octal
General specifications
Tube and section characteristics
Properties common to every published source and operating point.
Heater and base
- Base
- -
- Socket code
- IO
- Base pins
- -
- Nominal heater voltage
- 2 V
- Nominal heater current
- 60 mA
- Parallel heater voltage
- -
- Parallel heater current
- -
- Series capable
- No
Terminal pinout
Electrical assignments shared by every tube using this base designation.
No verified pinout is recorded for this base designation.
Section ratings
1 physical section, each with unique specifications.
Section 1
Pentode
X-ray radiationInterelectrode capacitances
- Plate resistance
- 800000 Ω
- Transconductance
- 0.00065 S
- Max plate voltage
- 135 V
- Max screen voltage
- 67.5 V
Published source values promoted where applicable; additional values retained as parameters.
Source-dependent data
Operating conditions by source
Each block preserves the test conditions and published values from one reference. Values from different sources are intentionally kept separate.