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  3. BARKER CX78

BARKER CX78 Williamson Capacitors Air Plate Tuning Cap Radio

Cx78 B&w Barker Williamson Capacitors Air Variable Plate Tuning Cap C Vintage Radio

( Brand: Barker ), ( Manufacturer Part Number: CX78 ), ( Model: BARKER WILLIAMSON CX78 C ), ( Type: Air Cap ), ( Color: Silver ), ( Band: B Amp;w ), ( Country Of Origin: United States )

Review BARKER Williamson Capacitors Air Variable Plate Tuning Cap Vintage Radio

The **CX78 Barker Williamson Air Plate Tuning Capacitor** is a meticulously crafted, high-performance variable capacitor designed for radio enthusiasts and vintage radio restorers seeking precision and reliability in their tuning circuits. This classic mechanical tuning capacitor, often referred to as a "Barker Williamson" due to its distinctive design, features a robust **air-dielectric variable capacitor** construction, ensuring minimal signal loss and exceptional stability across a wide frequency range. The unit is built with **high-quality brass or aluminum plates** that are meticulously machined to maintain consistent spacing, allowing for smooth and precise capacitance adjustments without the need for lubricants or maintenance. The capacitor s **rotary shaft mechanism** is engineered for durability, with a smooth, low-friction bearing system that ensures decades of reliable operation, making it an ideal choice for both modern and restored radios.

What sets the CX78 apart is its **dual-gang or single-gang configuration**, depending on the model, allowing for either independent or synchronized tuning adjustments. The **air-dielectric design** eliminates the issues associated with electrolytic or ceramic capacitors, such as capacitance drift, signal attenuation, or temperature sensitivity, making it perfect for high-frequency applications in shortwave, AM, and early FM receivers. The capacitor s **high Q factor** ensures minimal energy loss, delivering crisp, clear tuning with minimal distortion, which is essential for critical listening or experimental radio work. Additionally, the **mechanical robustness** of the Barker Williamson design makes it resistant to environmental factors like humidity and temperature fluctuations, ensuring consistent performance over time.

For collectors and restorers, the CX78 holds significant historical value, as it was widely used in mid-20th-century radio receivers, including models from brands like RCA, Philco, and Zenith. Its **vintage aesthetic**, combined with modern reliability, makes it a sought-after component for both functional restoration and aesthetic authenticity. Whether used in a fully restored vintage radio or integrated into a custom-built receiver, the CX78 Barker Williamson capacitor exemplifies the marriage of mechanical ingenuity and radio engineering, offering unmatched tuning precision and longevity. Its timeless design ensures that it remains a staple in the world of analog radio enthusiasts, bridging the gap between classic craftsmanship and contemporary performance.

The **CX78 Barker Williamson air plate tuning capacitor** is a classic, high-quality variable capacitor used primarily in vintage and restored amateur radio equipment, as well as in some shortwave listening (SWL) and experimental setups. Below is a detailed breakdown of its pros and cons, followed by a conclusion and recommendation.

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### **Pros of the CX78 Barker Williamson Capacitor**

1. **Superior Build Quality and Durability**

The CX78 is renowned for its robust construction, featuring high-grade brass plates, precision-machined insulators, and a sturdy metal case. This makes it far more durable than many modern plastic or ceramic capacitors, especially in high-power or high-Q applications. It can withstand significant mechanical stress without degrading performance.

2. **Exceptional Performance in RF Applications**

Barker Williamson capacitors are designed for high-frequency use, offering low loss and high Q (quality factor) even at UHF and microwave frequencies. This makes them ideal for regenerative receivers, crystal-controlled transmitters, and high-end SWL rigs where signal purity is critical.

3. **Precision and Consistency**

The air-dielectric design eliminates the capacitance drift and aging issues common in solid-dielectric capacitors (e.g., mica or ceramic). The capacitance remains stable over time, and the tuning action is smooth and repeatable. This is particularly valuable in critical tuning circuits like those in vacuum tube amplifiers or oscillators.

4. **Compatibility with Vintage Equipment**

The CX78 is a direct replacement for many capacitors found in older radio gear, such as those from the 1940s 1960s (e.g., Hallicrafters, Collins, or early Yaesu rigs). Its physical dimensions and electrical characteristics match original specifications, making it a seamless upgrade or replacement part.

5. **High Voltage Handling**

Barker Williamson capacitors are rated for high voltage applications (often 1000V or more), making them suitable for use in transmitters, power amplifiers, and high-voltage circuits where other capacitors might fail.

6. **Adjustability and Fine Tuning**

The air-plate design allows for precise capacitance adjustments, which is invaluable in critical tuning scenarios such as band-spreading or fine frequency adjustments in crystal-controlled circuits.

7. **Long Lifespan**

With proper care, a CX77 or CX78 can last decades without significant degradation. Unlike electrolytic or solid-dielectric capacitors, it does not dry out or lose capacitance over time.

8. **Aesthetic and Collectible Value**

For enthusiasts of vintage electronics, the CX78 is a prized component. Its classic design and craftsmanship make it a desirable part for restoration projects, adding both functional and aesthetic value.

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### **Cons of the CX78 Barker Williamson Capacitor**

1. **High Cost**

The CX78 is significantly more expensive than modern plastic or ceramic variable capacitors. For hobbyists on a budget, this can be a major drawback, especially when multiple units are needed for a project.

2. **Bulk and Physical Size**

Air-dielectric capacitors are physically larger and heavier than modern alternatives. This can be impractical in space-constrained builds or when replacing components in modern equipment designed for smaller parts.

3. **Sensitivity to Environmental Conditions**

While robust, the CX77/CX78 can be affected by humidity or dust if not properly sealed. Over time, moisture or debris can accumulate in the tuning mechanism, leading to sluggish operation or corrosion. Regular maintenance is required to keep it in optimal condition.

4. **Limited Availability of Replacement Parts**

If the capacitor fails, finding replacement parts (e.g., insulators, plates, or springs) can be challenging. While Barker Williamson still produces these capacitors, sourcing individual components may require special ordering or restoration services.

5. **Learning Curve for Maintenance**

Unlike plug-and-play modern capacitors, the CX78 requires occasional cleaning and lubrication to maintain smooth operation. This may be intimidating for beginners who prefer low-maintenance components.

6. **Not Ideal for Low-Frequency Applications**

While excellent for RF work, the CX78 is less efficient at very low frequencies (e.g., below 100 kHz). For audio or low-frequency tuning circuits, other types of capacitors (e.g., high-quality electrolytics or film capacitors) may be more practical.

7. **Potential for Mechanical Wear**

The tuning mechanism relies on mechanical precision, and over time, the shaft or springs may wear out, requiring adjustment or replacement. This is less of an issue with modern solid-state capacitors.

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### **Conclusion**

The **CX78 Barker Williamson air plate tuning capacitor** is one of the finest variable capacitors available for high-frequency and RF applications. Its unmatched build quality, precision, and reliability make it an indispensable component for vintage radio restoration, experimental RF work, and high-performance amateur radio setups. However, its high cost, physical size, and maintenance requirements may not make it suitable for every project or budget.

For **enthusiasts restoring classic radios, building high-Q RF circuits, or working with vintage equipment**, the CX78 is an excellent investment. For **modern, low-cost, or low-maintenance builds**, especially in non-RF applications, modern variable capacitors (e.g., high-quality ceramic or film types) may be more practical.

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### **Recommendation**

- **Buy the CX78 if:**

- You are restoring or modifying vintage radio equipment (e.g., Hallicrafters SX-110, Collins 75A-1, or similar).

- You are building or repairing high-performance RF circuits (e.g., regenerative receivers, crystal-controlled transmitters, or SWL rigs).

- You prioritize long-term reliability, precision tuning, and high voltage handling over cost or size.

- You are willing to invest in a component that will last decades with minimal maintenance.

- **Avoid the CX78 if:**

- You are working on a budget-sensitive project or need multiple variable capacitors.

- Your application involves low-frequency tuning (e.g., audio or power circuits).

- You prefer modern, compact, and low-maintenance components.

- You lack the space or inclination to perform occasional maintenance (e.g., cleaning and lubricating the tuning mechanism).

For most **modern amateur radio or general electronics projects**, a high-quality modern variable capacitor (e.g., a well-made ceramic or film type) may suffice. However, for **purists, restorers, or RF enthusiasts**, the CX78 remains the gold standard and is well worth the investment.

Details:

Barker Williamson Capacitors Air Variable Plate Tuning Cap CX78 c vintage radio, Untested.

part #: cx78 price

  • $40.00

specifications hamamateuradio:

  • brand: Barker
  • mpn: Cx78
  • model: Barker Williamson Cx78 C
  • type: Air Cap
  • color: Silver
  • band: B Amp;w
  • country of origin: United States

shipping hamamateuradio:

  • service: USPS Ground Advantage
  • carrier: USPS
  • cost: $31.50
  • class: Standard
  • transit: 4-10 Days
  • type: Fixed

general hamamateuradio:

  • Radio Communication > Ham, Amateur Radio > Ham Radio Amplifiers
  • condition: Used

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  • rating: 100.0%
  • # reviews: 3127
  • city: Mayfield, New York

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  • availability: In Stock
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  • started: March 3, 2026
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  • quantity: 1

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type: air cap, band: b amp;w, country of origin: united states,
category: electronics > radio communication > ham, amateur radio > ham radio amplifiers, color: silver, sku: 13556059093720723,
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