C178

Marconi twin tetrode designed for VHF Class-C amplifier and oscillator service to approximately 500 MHz. Two physical tetrode sections provide compact paired high-frequency power operation.

Directly heatedCold cathodeCommon cathodeDissimilar

Sections: 2
Base: -
Socket code: -
Base pins: -
Nominal heater: 12.6 V / 900 mA

Description

Twin tetrode for VHF Class-C amplifier and oscillator service to 500 MHz.

General specifications

Tube and section characteristics

Properties common to every published source and operating point.

Heater and base

Base: -
Socket code: -
Base pins: -
Nominal heater voltage: 12.6 V
Nominal heater current: 900 mA
Parallel heater voltage: 6.3 V
Parallel heater current: 1.8 A
Series capable: Yes

Terminal pinout

Electrical assignments shared by every tube using this base designation.

No verified pinout is recorded for this base designation.

Section ratings

2 physical sections, each with unique specifications.

Section 1

Tetrode

X-ray radiationInterelectrode capacitances

Transconductance: 0.0045 S
Max plate voltage: 750 V
Max screen voltage: 250 V
Max plate dissipation: 20 W

Section 2

Tetrode

X-ray radiationInterelectrode capacitances

Transconductance: 0.0045 S
Max plate voltage: 750 V
Max screen voltage: 250 V
Max plate dissipation: 20 W

Second identical physical tetrode section; added to align rows with SectionCount.

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

1955 Marconi

Published operating points and test conditions from this source.

SECTION 1

Tetrode

Characteristic

Heater Voltage Series
12.6 V
Both sections
Heater Current Series
900 mA
Both sections
Heater Voltage Parallel
6.3 V
Both sections
Heater Current Parallel
1.8 A
Both sections
Transconductance
4500 uS
Per section

Other

Maximum Anode Voltage
750 V
Per section
Maximum Screen Voltage
250 V
Per section
Maximum Anode Dissipation
20 W
Per section
Maximum Frequency
500 MHz

Capacitance

Grid-Anode Capacitance
0.1 pF
Per section
Input Capacitance
32 pF
Output Capacitance
10.5 pF
Screen Bypass Capacitance
2.1 pF