AC-118-137

The AC-118-137 is a professional-grade, fiberglass omnidirectional collinear antenna engineered for the VHF Aviation Band (118–137 MHz). This rugged, all-weather model is designed for critical Air Traffic Control (ATC) sites, providing reliable ground-to-ground and ground-to-air communication. Its center-fed design and vertically stacked elements ensure a high-fidelity radiation pattern and extended range without the need for complex multi-antenna installations.

Pattern Stability and RF Performance

The AC-118-137 features a sophisticated center-fed design that eliminates radiation pattern distortion, delivering a true 360-degree omnidirectional horizontal pattern. By stacking large-diameter brass radiating elements vertically and feeding them in phase, the antenna maintains a consistent 2 dBi gain across the entire aviation spectrum. A broad 78-degree vertical beam-width provides excellent hemispherical coverage, ensuring stable links with aircraft at various altitudes. To maintain signal purity, all junctions are fully welded, a critical feature that prevents inter-modulation (PIM) and ensures long-term electrical stability in high-density radio environments.

Military-Grade Durability

Built to survive the world’s most punishing climates, the internal brass and aluminum components are completely sealed within a high-strength fiberglass radome. This high-tech enclosure ensures survivability against abrasive sandstorms, acid rain, and UV radiation. The support pipe is manufactured from 6063T6 architectural-grade aluminum alloy, complemented by marine-grade stainless steel mounting hardware. This combination of materials makes the antenna highly resistant to salt-fog corrosion, satisfying MIL-STD-810G requirements. With a wind survival rating of 200 Km/Hr (125 MPH), it remains operationally secure during hurricane-force events.

Operational and Tactical Efficiency

The AC-118-137 is a "set-and-forget" solution that requires no field tuning or adjustments, significantly reducing setup time and technical overhead. For long-term reliability, the N-Female termination is housed at the very bottom of the antenna structure, providing 100% weather protection for the RF connection. Its compact 1.85-meter overall length and relatively light weight (3.5 Kgs) allow for easy handling and cost-effective shipping. This efficiency makes it an ideal choice for both permanent ATC hubs and rapidly deployable tactical command centers where reliable wideband VHF communication is paramount.

Detailed Technical Features

• Center-Fed Collinear Architecture: Unlike end-fed antennas that suffer from pattern "squint" or distortion, the center-fed design ensures a perfectly balanced horizontal radiation pattern for true 360° omnidirectional coverage.
• High Elevation Reach: Features a broad 78-degree vertical beam-width, providing the necessary hemispherical reach for reliable ground-to-air communication with aircraft at varying altitudes.
• Fully Welded Junctions: All internal electrical junctions are high-precision welded. This prevents Passive Inter-Modulation (PIM) and ensures a clean signal floor, which is critical at high-density radio sites with multiple co-located transmitters.
• Broadband Phase Matching: Utilizes vertically stacked, large-diameter brass radiating elements fed in-phase to maintain a consistent 2 dBi gain and a smooth VSWR of better than 2:1 across the entire 19 MHz bandwidth.
• Static & Lightning Protection: The internal radiating structure is designed to bleed off static noise and provides a low-resistance path to ground, protecting sensitive receiver front-ends from atmospheric transients.
• High Power Capacity: Rated for continuous RF power handling of 200 Watts, making it suitable for both standard voice communications and high-duty cycle data links.

Detailed Mechanical Features

• High-Strength Radome: The radiating array is completely sealed within a 45 mm diameter high-strength fiberglass tube. This radome acts as a primary shield against ice formation, UV radiation, and mechanical wear from bird strikes or sand erosion.
• Premium Material Engineering: Internal elements are fabricated from high-class brass, while the structural support pipe is made from 6063T6 architectural-grade aluminum alloy.
• Marine-Grade Hardware: Supplied with heavy-duty mounting brackets and fasteners manufactured from Type 316 stainless steel, ensuring zero oxidation in coastal or shipboard environments.
• Protected Feed Point: The N-Female termination is strategically located at the bottom of the antenna housing. This configuration allows the connector to be shielded from moisture and mechanical strain, effectively eliminating "connector rot."
• Compact Footprint:
  • Overall Length: 1.85 Meters (72.9 inches)
  • Net Weight: 3.5 Kgs (7.7 lbs)
  • Mounting: Designed for standard masts up to 51 mm (2 inches) in diameter.

Detailed Environmental Features (MIL-STD-810G)

The AC-118-137 is a fully ruggedized, all-weather model built to survive the most severe mission profiles:

• Hurricane-Force Wind Survival: Rated for wind speeds up to 200 Km/Hr (125 MPH), maintaining structural integrity and vertical alignment during severe storms.
• Extreme Thermal Range: Operational from -40°C to +70°C and storage-rated from -50°C to +80°C (Method 500.5/502.5).
• Corrosive Theater Protection: Fully tested for Salt Fog (Method 509.5) and acid rain resistance, making it essential for naval and island-based installations.
• Moisture & Fungus Resistance: Compliant with Method 507.5 (Humidity) and Method 508.6 (Fungus), ensuring zero performance degradation in tropical or jungle environments.
• Shock & Vibration Hardened: Built to withstand the mechanical stresses of Procedure IV (Shock) and Procedure I (Vibration), ensuring survival during transport in tactical vehicles or mounting on high-vibration platforms.

Technical Summary Comparison

Key Advantages

• Stable Hemispherical Coverage: The broad vertical beam ensures aircraft are never in a "null" zone as they approach or depart the airfield.
• Ruggedized Radome: Protects sensitive internal elements from mechanical wear, bird strikes, and ice formation.
• Rapid Deployment: Fully assembled and factory-tuned for immediate use upon arrival.

Primary Applications

• Military & Civilian ATC: Ground-to-air voice and data links for regional airfields.
• Tactical Command Posts: Reliable wideband VHF communication for mobile headquarters.
• Fixed Base Stations: Permanent installations for aeronautical weather and information relay.