RAYTHEON RK-28A Transmitting Vacuum Tube Ham Radio 803 Transmitter

( Brand: Raytheon ), ( Manufacturer Part Number: RK-28A ), ( Model: RAYTHEON RK-28A 803 ), ( Type: Vacuum Tube )

Review RAYTHEON 803 Transmitting Vacuum Tube Ham Radio Transmitter Usa

The **Raytheon RK-28A 803 Transmitting Vacuum Tube** is a legendary and highly sought-after component in the world of vintage and high-performance amateur radio communication, renowned for its reliability, durability, and exceptional performance in demanding RF (radio frequency) applications. Originally developed during the mid-20th century, this transmitting tube was specifically engineered to handle the rigorous demands of long-distance communication, making it a staple in both military and civilian ham radio setups of its era. The RK-28A belongs to the **803 series**, a family of high-power, air-cooled transmitting tubes designed to operate in the **HF (High Frequency) bands**, typically between 1.8 and 30 MHz, with the ability to deliver **up to 1,000 watts of continuous RF power** when properly paired with a suitable driver tube and power supply. Its robust construction features a **ceramic envelope** with **thoriated tungsten filaments**, ensuring long operational life even under heavy duty cycles, while its **indirectly heated cathode** design minimizes filament voltage fluctuations, contributing to stable and consistent performance.

One of the most distinctive and impressive aspects of the RK-28A is its **high efficiency and thermal management system**, which allows it to dissipate heat effectively through its **air-cooled anode and grid structures**, reducing the need for elaborate water-cooling systems that were common in earlier transmitting tubes. This design not only simplifies installation but also enhances reliability in field deployments, where cooling infrastructure might be limited. The tube s **beam-power tetrode configuration** with its carefully balanced grid and screen structures provides excellent gain and linearity, making it ideal for **CW (Continuous Wave), SSB (Single Sideband), and AM (Amplitude Modulation) transmissions** with minimal distortion. Its **high power handling capability** and **robust construction** also make it a favorite among vintage radio enthusiasts and DX (long-distance) operators who demand peak performance from their equipment.

Beyond its technical specifications, the RK-28A holds a special place in radio history as a symbol of mid-century engineering excellence. Originally used in military and commercial radio systems, it has since become a prized component in **restored vintage transmitters**, such as the iconic **Hallicrafters SX-101, Collins 30L-1, and Drake 2B**, where its presence elevates the performance of these classic rigs to new heights. Collectors and builders often seek out RK-28A tubes for their **authentic vintage aesthetic**, as well as their **proven track record of reliability** many of these tubes, when properly maintained, can still deliver decades of service with minimal degradation. However, due to their age and specialized nature, RK-28A tubes are no longer mass-produced, making them a rare and valuable find in today s market.

For the modern ham radio operator or vintage equipment enthusiast, the RK-28A represents a blend of **historical significance and cutting-edge performance** for its time. Its use in a well-maintained transmitter can unlock a level of **clarity, reach, and signal strength** that modern solid-state alternatives struggle to match, particularly in challenging propagation conditions. Whether integrated into a fully restored classic radio setup or repurposed into a custom-built transmitter, the RK-28A remains a testament to the golden age of tube technology a piece of radio history that continues to captivate and inspire those who appreciate the art of analog communication. For those willing to invest in its care including proper filament warm-up procedures, anode voltage regulation, and regular inspections for signs of wear the RK-28A 803 remains one of the most powerful and enduring transmitting tubes ever produced.

The **Raytheon RK-28A 803** is a classic vacuum tube linear amplifier designed for amateur radio (ham radio) use, particularly on the HF bands (1.8 30 MHz). Below is a detailed breakdown of its pros and cons, followed by a concluding recommendation.

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### **Pros of the Raytheon RK-28A 803**

1. **High Power Output**

The RK-28A is capable of delivering **1,000 watts PEP (CW) and 800 waters PEP (SSB)** on most HF bands, making it suitable for long-distance communication and contesting. This level of power is significantly higher than many modern solid-state amplifiers, which often max out around 1,000 watts but with less efficiency or reliability.

2. **Rugged and Reliable Design**

Built in the mid-20th century, the RK-28A was engineered for durability. Its vacuum tube technology (using 803A tubes) is known for longevity, especially when operated within specifications. Many units from this era, when properly maintained, can last decades with minimal issues beyond tube replacements.

3. **Wide Bandwidth and Flexibility**

The amplifier covers the entire HF spectrum (1.8 30 MHz) with minimal tuning adjustments, making it versatile for different modes (CW, SSB, AM) and bands. Unlike some modern amplifiers with narrower bandwidths, the RK-28A adapts well to a variety of operating styles.

4. **Low Cost of Ownership (Long-Term)**

While the initial purchase price may be higher than some solid-state alternatives, the cost of replacement tubes (803A) is relatively low compared to the expense of repairing or replacing modern RF amplifiers. Tubes typically last **10,000 30,000 hours** under normal use, and spare tubes are widely available.

5. **No Heat or Power Supply Issues**

Unlike solid-state amplifiers, which can suffer from heat-related failures (e.g., blown MOSFETs, transformer failures), vacuum tubes do not degrade due to thermal cycling. The RK-28A s power supply and cooling system are straightforward and less prone to catastrophic failure.

6. **Aesthetic and Historical Appeal**

For enthusiasts who appreciate vintage electronics, the RK-28A is a well-designed, functional piece of ham radio history. Its robust construction and classic design make it a desirable collector s item.

7. **Good Efficiency**

Vacuum tube amplifiers like the RK-28A are generally more efficient than early solid-state designs, though not as efficient as modern Class D or E amplifiers. However, for its era, it performs well with power conversion efficiencies around **60 70%**.

8. **Minimal Maintenance Requirements**

With proper operation (e.g., avoiding overdriving, ensuring proper cooling), the RK-28A requires little maintenance beyond occasional tube checks and cleaning of contacts. There are no capacitors or resistors to fail due to aging, as in solid-state gear.

9. **Compatibility with Older Equipment**

If you operate vintage radios or transmitters, the RK-28A integrates seamlessly with them. It s also compatible with modern rigs, though you may need to adjust drive levels to avoid overdriving the tubes.

10. **Proven Performance in Contests and DX**

Many hams who use the RK-28A report excellent performance in contests and DX (long-distance) operations, attributing its reliability and power to consistent results.

---

### **Cons of the Raytheon RK-28A 803**

1. **High Initial Cost**

The RK-28A is not cheap to purchase, especially in good working condition. Prices can range from **$1,500 to $3,000 **, depending on the unit s condition, age, and whether it comes with spare tubes or documentation. This is significantly more expensive than many modern solid-state amplifiers offering similar power.

2. **Requires Expertise to Operate and Maintain**

- Proper tube handling (avoiding static discharge, ensuring correct orientation).

- Cooling requirements (fans, airflow, and ambient temperature).

- Drive level adjustments to prevent tube damage.

- Troubleshooting techniques (e.g., identifying tube failures, checking for arcing).

If you re not comfortable with electronics, this amplifier may be frustrating to maintain.

3. **Bulk and Space Requirements**

The RK-28A is a large, heavy unit (weighing around **100 120 lbs**). It requires dedicated space in your shack, which may not be feasible for those with limited room. The power supply and cooling system also take up significant space.

4. **Power Consumption**

At full power, the RK-28A draws **around 1,200 1,500 watts** from the mains, which can be a concern for hams with limited electrical capacity or high electricity costs. This is comparable to some solid-state amplifiers but may be higher than smaller tube amps.

5. **Limited Modern Features**

- Digital displays or controls.

- Built-in protection circuits (e.g., overvoltage, overcurrent).

- Remote control capabilities.

- Automatic tuning or band-switching.

These features are often taken for granted in contemporary gear but require manual adjustments on the RK-28A.

6. **Tube Replacement Costs Over Time**

While individual 803A tubes are affordable (typically **$50 $100 each**), replacing all four tubes in the amplifier can add up. Over the lifespan of the amp, you may need to budget for multiple tube replacements, especially if you operate it frequently.

7. **Potential for Arcing or Failure**

- **Arcing** (if the tube is overdriven or the grid is not properly biased).

- **Filament burnout** (if the tube is not properly heated or operated).

- **Grid or plate failures** (due to voltage spikes or poor cooling).

While rare with proper operation, these failures can be costly and time-consuming to diagnose.

8. **Limited Availability of Spare Parts**

While the 803A tube is still produced, finding original Raytheon components (e.g., capacitors, resistors, transformers) can be difficult if the amp requires repairs beyond tube replacement. Some units may need custom wiring or part substitutions.

9. **Not Ideal for Portable or Field Operations**

Due to its size, weight, and power requirements, the RK-28A is impractical for portable or field-day setups. It s designed for shack use only.

10. **Learning Curve for Modern Hams**

Many younger or less experienced hams are more familiar with solid-state amplifiers, which are generally easier to operate and troubleshoot. The RK-28A s operation may feel outdated or complex to those accustomed to modern gear.

---

### **Conclusion**

The **Raytheon RK-28A 803** is a **high-performance, durable, and reliable** amplifier that excels in power output, longevity, and historical significance. It is an excellent choice for:

- **Serious contesters and DXers** who prioritize raw power and reliability.

- **Enthusiasts who appreciate vintage electronics** and are willing to invest time in maintenance.

- **Hams with experience in tube operation** who understand the nuances of driving and cooling tubes.

- **Those with dedicated shack space** and no concerns about bulk or aesthetics.

- **Beginners or casual operators** who prefer simplicity and modern features.

- **Hams with limited technical skills** or patience for troubleshooting.

- **Those on a tight budget**, as the initial cost and long-term tube replacements add up.

- **Portable or field operators** due to its size and power requirements.

---

### **Recommendation**

- You are an experienced ham with a strong interest in tube amplifiers and have the technical skills to maintain it.

- You operate in contests or need reliable high power for DX.

- You value the historical and aesthetic appeal of vintage gear.

- You have the space and budget to accommodate its size and cost.

- You prefer modern, user-friendly amplifiers with built-in protections and digital controls.

- You lack experience with vacuum tubes or are unwilling to learn their operation.

- You operate on a limited budget or cannot justify the long-term costs of tube replacements.

- You need portability or plan to use the amp in field conditions.

- **Solid-state amplifiers** (e.g., **Amateur Electronics RX-330, Icom IC-7000 with external amp, or Yaesu FT-1000MP with external amp**) for ease of use and modern features.

- **Smaller tube amplifiers** (e.g., **Kenwood TS-990S, Icom IC-756PRO III**) for those who want tube performance without the bulk of the RK-28A.

- **Hybrid setups** (e.g., a modern transceiver with a **solid-state linear like the **Amateur Electronics RX-330** or **KPA-1500**) for a balance

Details:

Please review all photos carefully for condition and identification. Sold as collectible vintage electronic component. Genuine Raytheon USA manufacture. Removed from a long-time radio collectors estate.

Large ceramic base transmitting tube. Cosmetic wear consistent with age. Equivalent to Type 803 transmitting tube. Vintage Raytheon RK-28A transmitting vacuum tube.

Glass appears intact with no visible cracks.

part #: rk28a price

• $149.99

specifications tubesocketvintagego:

• brand: Raytheon
• mpn: Rk-28a
• model: Raytheon Rk-28a 803
• type: Vacuum Tube

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• started: June 12, 2026
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• condition: For parts or not working

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