AMPEREX HF-140 Transmitting Triode Bottom Tube

( Brand: Amperex ), ( Manufacturer Part Number: HF-140 ), ( Type: Vacuum Tube )

Review AMPEREX Pair Vintage Original Transmitting Triode Gold Bottom Tube

The **Amperex HF-140 Transmitting Triode** is a high-performance, ruggedized glass-envelope vacuum tube designed for demanding applications in amateur radio, shortwave broadcasting, and experimental electronics. As a member of the legendary **HF series** from Amperex, this tube is engineered to deliver exceptional power handling, reliability, and efficiency in transmitting circuits, making it an ideal choice for builders and operators seeking superior performance in high-frequency (HF) and VHF systems. The HF-140 is a **beam power tetrode** (often misclassified as a triode due to its internal construction), featuring a **thoriated tungsten cathode** that ensures long operational life and consistent emission even under heavy duty cycles. Its **ceramic-to-metal sealed construction** provides exceptional thermal stability, reducing the risk of catastrophic failure under high-power conditions, while the **heavy-duty glass envelope** is designed to withstand the thermal and mechanical stresses of continuous operation.

Internally, the HF-140 employs a **four-electrode structure**, including a **thoriated tungsten cathode**, a **helical control grid**, a **screen grid**, and a **plated molybdenum anode (plate)**, all housed within a **high-vacuum environment** to minimize gas evolution and maintain optimal performance. The tube s **beam-focused design** ensures efficient electron flow, reducing interelectrode capacitance and improving linearity in modulated signals a critical advantage for SSB (Single Sideband) and CW (Continuous Wave) transmissions. With a **rated power dissipation of up to 150 watts** (P3E) and a **peak power capability exceeding 300 watts**, the HF-140 excels in high-power amplifier stages, exciter circuits, and even as a driver tube in larger transmitter assemblies. Its **low noise figure** and **high gain** make it particularly well-suited for applications requiring clean, efficient amplification with minimal distortion.

The HF-140 s **robust mechanical design** includes a **ceramic-to-metal seal** that enhances thermal conductivity, preventing hotspots that could lead to premature failure. The tube s **heavy-duty glass envelope** is reinforced to resist thermal shock, making it ideal for both bench-top and field-use scenarios where stability is paramount. When properly operated within its specified parameters typically **6.3V filament voltage (5.5 7.5V range) and 1200 1500V plate voltage** the HF-140 delivers **exceptional efficiency**, often exceeding **70% plate efficiency** in properly matched circuits. This makes it a favorite among radio enthusiasts and professional builders who demand **high power output with minimal heat generation**, reducing the need for oversized cooling solutions.

Beyond its technical specifications, the HF-140 is celebrated for its **reliability and longevity**, often outperforming modern solid-state alternatives in terms of durability and consistency. Its **thoriated tungsten cathode** ensures **thousands of hours of operation** under proper conditions, while its **low interelectrode capacitance** (typically **1.5 2.5 pF**) minimizes signal loss and improves bandwidth in high-frequency applications. Whether used in **amateur radio transmitters, experimental RF amplifiers, or vintage radio restoration projects**, the HF-140 remains a **benchmark tube** for those who prioritize **performance, efficiency, and build quality** over modern convenience. For builders working with **10-meter through 20-meter bands**, the HF-140 provides an unmatched combination of **power, linearity, and reliability**, making it a **must-have component** for serious radio enthusiasts and professionals alike.

The Amperex HF-140 is a high-performance transmitting triode tube, often used in amateur radio, broadcast, and experimental applications. Below is a detailed breakdown of its pros and cons, followed by a concluding recommendation.

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### **Pros of the Amperex HF-140**

1. **High Power Handling**

The HF-140 is designed for high-power applications, capable of handling significant plate dissipation (up to 150W average and 300W peak) and high current levels. This makes it suitable for high-efficiency amplifiers, especially in HF (High Frequency) and VHF (Very High Frequency) transmitters.

2. **Excellent Frequency Response**

It exhibits a broad frequency range, typically from around 1.8 MHz to 30 MHz (and sometimes higher with proper design), making it versatile for amateur radio bands, including the HF spectrum. Its performance remains stable across a wide bandwidth, which is advantageous for multi-band operation.

3. **High Efficiency**

The HF-140 is known for its efficiency, often achieving plate efficiencies of 60-70% or higher in properly designed circuits. This reduces heat dissipation and power consumption, which is beneficial for both cost and reliability.

4. **Durability and Longevity**

Amperex tubes are generally built to high standards, with robust construction and reliable glass-to-metal seals. The HF-140, in particular, has a reputation for longevity when operated within its specifications, though proper cooling and maintenance are essential.

5. **Compatibility with Modern and Classic Circuits**

The HF-140 can be used in both modern solid-state-driven amplifiers and traditional vacuum tube circuits. Its characteristics make it adaptable to various amplifier designs, including those using linear amplifiers, RF power amplifiers, and even some experimental setups.

6. **Low Noise Figure (in Receiver Applications)**

While primarily a transmitting tube, the HF-140 can also be used in low-noise preamplifier stages in receivers, thanks to its low noise characteristics at lower power levels. This duality adds to its utility.

7. **Availability of Replacement Parts**

Amperex tubes, including the HF-140, are still manufactured and distributed by companies like Amperex Electronics Corporation and its subsidiaries. This ensures availability of replacements and spare parts, though sourcing may require some effort depending on location.

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### **Cons of the Amperex HF-140**

1. **High Voltage Requirements**

The HF-140 operates at high voltages, typically requiring a plate voltage of 1200V to 2000V (depending on the circuit). This necessitates careful handling, proper insulation, and potentially expensive high-voltage power supplies. Mishandling high voltages poses a significant safety risk.

2. **Heat Generation and Cooling Needs**

Despite its efficiency, the HF-140 generates substantial heat, especially at high power levels. Adequate cooling is required, often involving large heat sinks, forced air cooling, or even liquid cooling in high-power applications. Poor cooling can lead to tube failure or reduced lifespan.

3. **Complexity in Circuit Design**

Properly designing an amplifier around the HF-140 requires a good understanding of RF circuits, impedance matching, and tube characteristics. Beginners or those without experience in tube amplifier design may struggle with tuning, matching, and optimizing performance.

4. **Cost**

The HF-140 is not a cheap tube. Prices can range from $200 to $500 or more, depending on the seller and condition. Additionally, the cost of associated components (e.g., high-voltage power supplies, heat sinks, and cooling fans) can add up significantly, making it a substantial investment.

5. **Sensitivity to Operating Conditions**

The tube is sensitive to overvoltage, overcurrent, and improper biasing. Operating it outside its specified parameters can lead to immediate failure or gradual degradation. This requires careful monitoring and adjustment during operation.

6. **Limited Availability of Supporting Components**

While the tube itself is available, finding compatible high-voltage components (e.g., transformers, capacitors, and power supplies) can be challenging, especially for older or niche designs. This may require custom fabrication or sourcing from specialized suppliers.

7. **Learning Curve for Maintenance**

Tube amplifiers require more maintenance than solid-state amplifiers. This includes checking for vacuum leaks, cleaning contacts, and replacing worn-out parts. Users must be willing to invest time in learning and maintaining the equipment.

8. **Size and Physical Constraints**

The HF-140 is a large tube, occupying significant space in an amplifier chassis. This can be a limitation in compact or portable setups where space is at a premium.

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### **Conclusion**

The Amperex HF-140 is a powerful and versatile tube amplifier tube, ideal for high-power transmitting applications in amateur radio, broadcast, and experimental RF work. Its high efficiency, broad frequency range, and durability make it a favorite among experienced tube enthusiasts and operators. However, its high voltage requirements, heat generation, complexity in design, and cost present significant challenges, particularly for beginners or those without prior experience in tube amplifier construction and maintenance.

For users who are well-versed in RF circuits, high-voltage handling, and tube amplifier design, the HF-140 offers unmatched performance and reliability. For those new to tube amplifiers or working with limited resources, the challenges may outweigh the benefits, making it less suitable.

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### **Recommendation**

- You are an experienced amateur radio operator or RF engineer with knowledge of high-voltage circuits and tube amplifier design.

- You are building a high-power HF or VHF transmitter or amplifier and require a tube with excellent efficiency and frequency response.

- You have access to proper cooling, high-voltage power supplies, and supporting components.

- You are willing to invest time in learning and maintaining the tube amplifier.

- You are a beginner in tube amplifier construction or lack experience with high-voltage electronics.

- You do not have the space, budget, or resources to properly cool and power the tube.

- You are looking for a simple, low-maintenance solution and are willing to compromise on power and efficiency for ease of use.

- You prefer solid-state amplifiers, which are generally more user-friendly and require less maintenance.

For those on a budget or seeking a more accessible alternative, consider lower-power tubes like the 4CX3500A or 3-500Z, which offer a balance between performance and complexity. Alternatively, solid-state amplifiers like the Yaesu FT-1000MP or Icom IC-7800 provide high performance with minimal maintenance. However, if your project demands the power, efficiency, and performance of a high-end tube amplifier, the HF-140 remains one of the best choices available.

Details:

This item was pulled from a working environment. Only items included in pictures are the sale. Please look at all photos before purchasing. Tested and Working.

part #: hf140 prices

• $395.00-$1499.99

specifications tubesocketvintagego:

• brand: Amperex
• mpn: Hf-140
• type: Vacuum Tube

returns tubesocketvintagego:

• time: 30 Days
• paid by: Seller
• policy: Returns Accepted
• method: Money back

shipping tubesocketvintagego:

• class: Standard
• carrier: UPS
• cost: $20.00
• service: UPS Ground
• type: Fixed
• transit: 3-7 Days

seller tubesocketvintagego:

• city: San Diego, California
• rating: 99.3%
• # reviews: 13010

offer tubesocketvintagego:

• started: May 26, 2026
• availability: In Stock
• sold: 0
• quantity: 1
• options: Ship-to-home
• best offers: True

payments tubesocketvintagego:

• credit card: Visa
• wallet: Paypal
• other

general tubesocketvintagego:

• condition: Used
• Vintage Audio Video > Vintage Parts Accessories > Vintage Tubes Tube Sockets

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