18FX6A

Miniature heptode frequency converter combining oscillator and mixer functions in one tube. Electrically related to the 18FX6 but with controlled heater characteristics, it is designed for low-current series-heater superheterodyne receivers.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 1
Base: -
Socket code: B7G
Base pins: 7
Nominal heater: 18 V / 100 mA

Description

The 18FX6A is a dual-control pentagrid converter/amplifier for AC/DC radio receivers, electrically equivalent to the 18FX6 except for controlled heater characteristics.

Socket description

Miniature 7-contact

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: B7G
Base pins: 7
Nominal heater voltage: 18 V
Nominal heater current: 100 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

Heptode

X-ray radiationInterelectrode capacitances

Plate resistance: 400000 Ω
Transconductance: 0.00048 S
Amplification factor: 22
Max plate voltage: 150 V
Max screen voltage: 110 V
Max plate dissipation: 1 W
Max screen dissipation: 1.2 W
Max cathode current: 24 mA

Pentagrid converter; oscillator data 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.

Data set 01

1961 Tung Sol

Published operating points and test conditions from this source.

SECTION 1

Heptode

Characteristic

Conversion Transconductance
480 uS
SeparateExcitation
OscillatorModeTransconductance
7000 uS
Grid2AndGrid4ConnectedToPlate
OscillatorModeAmplificationFactor
22
Grid2AndGrid4ConnectedToPlate

Other

Heater Warmup Time
20 s

Data set 02

1966 Tung Sol Electronic Tubes 3 of 4

Published operating points and test conditions from this source.

SECTION 1

Heptode

Characteristic

Grid 3-to-plate capacitance
0.25 pF
WholeTube
Grid 3-to-grid 1 capacitance
0.15 pF
WholeTube
Input capacitance
7 pF
WholeTube
Output capacitance
13 pF
WholeTube

Other

Maximum plate voltage
150 V
WholeTube
Maximum grids 2 and 4 voltage
110 V
WholeTube
Maximum plate dissipation
1 W
WholeTube
Maximum grids 2 and 4 dissipation
1.2 W
WholeTube
Plate voltage
200 V
TypicalOperation
Grid 2 voltage
100 V
TypicalOperation
Grid 3 voltage
-1.5 V
TypicalOperation
Plate current
2.3 mA
TypicalOperation
Grid 2 current
6.2 mA
TypicalOperation
Conversion transconductance
450 µS
TypicalOperation
Plate resistance
400000 ohm
TypicalOperation
Triode-connected transconductance
7000 µS
TypicalOperation
Triode-connected amplification factor
22
TypicalOperation

Data set 03

1971 RCA HB3 Binder 5 of 7

Published operating points and test conditions from this source.

SECTION 1

Heptode

Other

Heater voltage
18 V
Heater current
100 mA
Heater warm-up time
20 s
ControlledWarmup
Maximum plate voltage
150 V
Converter
Maximum screen supply voltage
150 V
Converter
Screen voltage
110 V
Converter
Screen input
1.2 W
Converter
Plate dissipation
1 W
Converter
Peak heater-cathode voltage heater negative
100 V
Peak heater-cathode voltage heater positive
100 V
Plate voltage
100 V
Converter
Screen voltage
100 V
Converter
Grid No.3 voltage
-1.5 V
Converter
Grid No.1 resistor
20000 ohm
Converter
Plate current
2.3 mA
Converter
Screen current
6.2 mA
Converter
Oscillator grid current
0.5 mA
Converter
Total cathode current
9 mA
Converter
Oscillator cathode current
24 mA
Oscillator

Characteristic

Plate resistance
400000 ohm
Converter
Conversion transconductance
480 uS
Converter
Grid No.3 voltage for conversion transconductance 10 uS
-21 V
Converter
Oscillator amplification factor
22
Oscillator
Oscillator transconductance
7000 uS
Oscillator

Capacitance

RF input capacitance grid No.3
7 pF
Mixer output capacitance plate
8 pF
WithoutShield
Oscillator input capacitance grid No.1
5.5 pF