RF Power Grid Tubes · Tetrodes
4-125A Beam Power Tetrode
Classic beam power tetrode with 125 W plate dissipation, widely used in HF and VHF exciters and low-power transmitter stages.
- Plate Dissipation
- 125 W
- Max Frequency
- 175 MHz
- Max Plate Voltage
- 2.0 kV
- Max Plate Current
- 125 mA
About the 4-125A
The 4-125A is a power tetrode. Classic beam power tetrode with 125 W plate dissipation, widely used in HF and VHF exciters and low-power transmitter stages.
Key ratings of the 4-125A include tube type Beam Power Tetrode, plate dissipation 125 W, max plate voltage 2.0 kV, max plate current 125 mA, screen voltage 250 V and transconductance 20 mA/V.
Typical applications are HF exciter stages, VHF FM low-power transmitters, amateur radio amplifiers and instrumentation RF oscillators. Notable features: compact 125 W design, up to 175 MHz operation, industry-standard HF/VHF tube and long production history.
Power tetrodes add a screen grid to the triode structure, giving higher gain and lower drive power. They are widely used in FM and TV broadcast transmitters, HF communications, plasma heating and accelerator RF systems, usually together with vacuum capacitors in the output network.
PartnerTubes supplies the 4-125A worldwide from Groningen, the Netherlands — availability, lead time and price are confirmed per enquiry. Our team can help with equivalent and cross-reference types, sockets and accessories, and supply programmes for OEM and maintenance customers. Interchangeability must always be confirmed for the specific equipment.
Technical specifications
| Tube Type | Beam Power Tetrode |
|---|---|
| Plate Dissipation | 125 W |
| Max Plate Voltage | 2.0 kV |
| Max Plate Current | 125 mA |
| Screen Voltage | 250 V |
| Transconductance | 20 mA/V |
| Max Frequency | 175 MHz |
| Filament Voltage | 6.3 V |
| Filament Current | 2.0 A |
Specifications are indicative and based on published manufacturer data. Always verify against the official datasheet and confirm suitability for your application before ordering.
Applications & features
Used in
- HF exciter stages
- VHF FM low-power transmitters
- Amateur radio amplifiers
- Instrumentation RF oscillators
Key features
- Compact 125 W design
- Up to 175 MHz operation
- Industry-standard HF/VHF tube
- Long production history
Related parts & equivalents
Recommended alongside or as alternatives to the 4-125A.
Similar RF Power Grid Tubes
Comparable type, ratings, manufacturer or applications.
Vacuum capacitors for output networks
Often ordered with the 4-125A for the same system.
Jennings UCSL 25–200 pF Variable Vacuum Capacitor 25 kV
Jennings Technology (CPI)
Frequently asked questions
What is the 4-125A?
The 4-125A is a power tetrode. Classic beam power tetrode with 125 W plate dissipation, widely used in HF and VHF exciters and low-power transmitter stages.
What are the specifications of the 4-125A?
Tube Type: Beam Power Tetrode; Plate Dissipation: 125 W; Max Plate Voltage: 2.0 kV; Max Plate Current: 125 mA; Screen Voltage: 250 V; Transconductance: 20 mA/V; Max Frequency: 175 MHz; Filament Voltage: 6.3 V; Filament Current: 2.0 A.
What is the 4-125A used for?
The 4-125A is used in HF exciter stages, VHF FM low-power transmitters, amateur radio amplifiers and instrumentation RF oscillators.
What are alternatives or related parts to the 4-125A?
Related and comparable parts include 4-400A, 4CX250B, 4CX350A, GU-74B, 4CX250R and 4CX600J. Contact PartnerTubes to confirm interchangeability for your equipment.
Where can I buy the 4-125A?
The 4-125A is available from PartnerTubes (Grunius BV, Groningen, Netherlands) with worldwide shipping. Availability and lead time are confirmed on request. Request a quote at https://www.partnertubes.com/contact/?part=4-125A or email info@partnertubes.com.