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Power - Pentode (NOT beam) ·Pentode

306A

Power pentode designed primarily for Class-C radio-frequency transmitting, amplifier, oscillator, or modulated RF service.

Directly heatedCold cathodeCommon cathodeDissimilar
Sections
1
Base
-
Socket code
UX4
Base pins
4
Nominal heater
2.75 V / 2 A

Description

Air-cooled transmitting pentode for Class C RF plate-modulated service.

Socket description

Medium-shell UX 4-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base
-
Socket code
UX4
Base pins
4
Nominal heater voltage
2.75 V
Nominal heater current
2 A
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
Transconductance
0.00405 S
Max plate voltage
300 V
Max screen voltage
300 V
Max plate dissipation
15 W
Max cathode current
60 mA

Promoted fields audited from printed ratings/characteristics; remaining published values preserved 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.

Data set 01

1956 Western Electric Tubes

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristic

  • HeaterOrFilamentVoltage

    2.75 V

  • HeaterOrFilamentCurrent

    2 A

Other

  • Typical Power Output

    7 W

    ClassC;PlateModulated

Data set 02

2026 Western Electric 300s

Published operating points and test conditions from this source.

SECTION 1

Pentode

Characteristic

  • Audio-frequency amplifier in positions where power outputs of approximately

    8 watts

    Audio-frequency amplifier in positions where power outputs of approximately 8 watts or less

  • Filament voltage

    2.75 volt

    Filament voltage 2.75 volts, a.c. or d.c.

  • Nominal fi l a m e n t current

    2 amperes

    Nominal fi l a m e n t current 2.0 amperes

  • former secondary. When the tube is used in very high-frequency circuits,

    20 second

    former secondary. When the tube is used in very high-frequency circuits, 20 megacycles or above,

  • are shown in Figures

    3 volt

    are shown in Figures 3 and 4, respectively, as functions of control-grid voltage for several values

  • voltage in Figures

    5 volt

    voltage in Figures 5 and 6, respectively, for a screen-grid voltage of 300 volts. Corresponding

  • amplification factor, plate resistance, and transconductance characteristics are shown in Figures

    7

    amplification factor, plate resistance, and transconductance characteristics are shown in Figures 7,

  • swing of input voltage +

    30 volt

    swing of input voltage +30 volts

  • frequency a m p l i fi c a t i o n

    50 milliamperes

    frequency a m p l i fi c a t i o n 50 milliamperes

  • ABCDE, in Figure

    3

    ABCDE, in Figure 3. Amplification factor, plate resistance, transconductance, and performance

  • voltage for several values of load resistance are shown in Figures

    10 volt

    voltage for several values of load resistance are shown in Figures 10, 11 and 12, respectively, for

  • Direct plate voltage

    300 volt

    Direct plate voltage 300 volts

  • Direct screen-grid voltage (approximate)

    180 volt

    Direct screen-grid voltage (approximate) 180 volts

  • Screen-grid circuit resistance

    8000 ohms

    Screen-grid circuit resistance 8000 ohms

  • Control-grid circuit resistance

    10000 ohms

    Control-grid circuit resistance 10000 ohms

  • Fixed control-grid bias

    -20 volts

    Fixed control-grid bias —20 volts

  • R-F control-grid driving voltage

    70 volt

    R-F control-grid driving voltage 70 peak volts

  • Direct plate current

    36 milliamperes

    Direct plate current 36 milliamperes

  • Direct screen-grid current

    15 milliamperes

    Direct screen-grid current 15 milliamperes

  • Direct control-grid current

    3 milliamperes

    Direct control-grid current 3 milliamperes

  • Effective load resistance

    4500 ohms

    Effective load resistance 4500 ohms

  • Carrier power output

    7 watts

    Carrier power output 7 watts

  • Power output on a-f peaks

    28 watts

    Power output on a-f peaks 28 watts

  • and to the screen grid through the

    8000 ohm

    and to the screen grid through the 8000 ohm screen-grid resistance. No by-pass condenser is used

  • PLATE VOLTAGE =

    300 VOLT

    PLATE VOLTAGE = 300 VOLTS [

  • FILAMENT VOLTAGE =

    2.75 VOLT

    FILAMENT VOLTAGE =2.75 VOLTS DCf

  • SCREEN-GRID VOLTAGE =

    300 VOLT

    SCREEN-GRID VOLTAGE = 300 VOLTS E

  • CONTROL-GRID VOLTAGE =

    -20 VOLT

    CONTROL-GRID VOLTAGE = -20 VOLTS E

Other

  • Maximum plate voltage

    300 volt

    Maximum plate voltage 300 volts

  • Maximum screen-grid voltage

    300 volt

    Maximum screen-grid voltage 300 volts

  • Maximum plate current for audio-frequency amplifier applications

    60 milliamperes

    Maximum plate current for audio-frequency amplifier applications 60 milliamperes

  • Maximum plate dissipation

    15 watts

    Maximum plate dissipation 15 watts

  • Maximum screen-grid current

    20 milliamperes

    Maximum screen-grid current 20 milliamperes

  • Maximum control-grid current

    7 milliamperes

    Maximum control-grid current 7 milliamperes

  • columns of the table to other maximum harmonic levels. Each ordinate in Figure

    13

    columns of the table to other maximum harmonic levels. Each ordinate in Figure 13 gives the

  • Maximum direct plate voltage

    300 volt

    Maximum direct plate voltage 300 225 volts

  • Maximum direct plate current

    50 milliamperes

    Maximum direct plate current 50 50 milliamperes