AC6-840

AC6-840: High-Gain Omni-Directional Collinear Antenna for TETRA Networks

The AC6-840 is a professional-grade, high-performance TETRA Band Collinear Antenna specifically engineered for the 806–870 MHz frequency range. Designed to provide a powerful 6 dBd (8.15 dBi) gain, this center-fed antenna ensures a true omni-directional radiation pattern with zero distortion, making it the definitive choice for critical public safety, military, and industrial communication hubs. Fully MIL-STD-810G compliant, the AC6-840 is housed in a ruggedized fiberglass radome and constructed with marine-grade materials to ensure persistent performance in the most challenging environmental conditions.

Design: Superior Gain and Pattern Stability

The AC6-840 utilizes a sophisticated center-fed collinear design that eliminates the pattern distortion often found in end-fed antennas. By stacking large-diameter brass radiating elements vertically and feeding them in phase, the antenna achieves a highly focused 18-degree vertical beamwidth. This concentration of RF energy toward the horizon results in a constant 6 dBd (8.15 dBi) gain, providing vastly superior range and signal penetration for TETRA network infrastructure. Specialized stub matching ensures a smooth VSWR of less than 1.5:1 across the entire bandwidth, maximizing transmitter efficiency.

Construction: MIL-SPEC Environmental Hardening

Engineered for ultimate survivability, the AC6-840 features a 6063T6 architectural aluminum support pipe and high-class brass alloys. All internal junctions are fully welded to prevent passive inter-modulation (PIM) and ensure long-term electrical stability. The entire radiating structure is protected within a high-tech heavy-duty fiberglass radome that offers excellent RF transparency and mechanical strength. With a wind rating of 200 Km/Hr and a 316 marine-grade stainless steel mounting system, this antenna is purpose-built for coastal installations, high-altitude masts, and severe weather environments.

Reliability: Tested to the Highest Standards

The AC6-840 is built to meet rigorous MIL-STD-810G specifications, ensuring reliability against shock, vibration, salt fog, and extreme temperatures ranging from -30°C to +70°C. Its 1.35-meter compact profile is finished in a tactical olive green powder coating, providing an aesthetically pleasing yet low-visibility signature. With a massive RF power handling capacity of 400 Watts, the AC6-840 is a robust and dependable solution for high-traffic TETRA base stations where downtime is not an option.

Technical Features

• Optimized 806–870 MHz TETRA Coverage: Purpose-built for peak performance in the international TETRA frequency bands.
• High-Intensity 6 dBd (8.15 dBi) Gain: Collinear stacking provides an extended communication range for base station deployments.
• Center-Fed Architecture: Ensures a perfect 360° omni-directional horizontal pattern with no pattern uptilt or distortion.
• MIL-STD-810G Certified: Rigorously tested for durability against rain, humidity, fungus, salt fog, and mechanical shock.
• Welded Internal Junctions: Eliminates RF inter-modulation and ensures a stable electrical lifecycle.
• Marine Grade Hardware: Includes Type 316 stainless steel mounting components for maximum corrosion resistance.
• Heavy-Duty Fiberglass Radome: 45mm diameter enclosure provides ultimate protection while maintaining high RF efficiency.
• 400W Power Capacity: Capable of handling high-power transmissions for multi-channel TETRA trunking systems.
• Weather-Shielded Termination: The N-Female input termination is enclosed at the bottom to prevent moisture ingress.
• Maintenance-Free Design: Factory-calibrated for immediate "plug-and-play" installation with no field tuning required.

TETRA Network Optimization Guide: Maximizing Coverage with the AC6-840

In critical communications, particularly for Public Safety and Industrial trunked radio systems, the AC6-840 acts as a high-efficiency signal multiplier. By focusing RF energy where it is needed most—along the horizon—this 6 dBd gain antenna ensures that "dead zones" are minimized and network reliability is maximized.

1. The Power of the 18-Degree Vertical Beamwidth

Standard unity-gain antennas radiate energy in a large, "donut-shaped" pattern that wastes signal by sending it into the sky or directly into the ground near the tower.

• The High-Gain Advantage: The AC6-840 uses collinear stacking to compress the vertical beam into a tight 18-degree window. This concentrated "disk" of RF energy travels much further along the earth's surface.
• Urban Penetration: In high-density urban environments, this focused beam allows the TETRA signal to "punch through" concrete structures and reflect off buildings more effectively, reaching handheld radios inside basements or dense alleyways that lower-gain antennas might miss.

2. Center-Fed Architecture: Eliminating Pattern Distortion

Many wideband antennas are "end-fed," which can cause the radiation pattern to "tilt" upward or downward as the frequency changes (a phenomenon known as pattern squint).

• True Omni-Directional Coverage: The AC6-840 is Center-Fed, ensuring the signal is distributed with 100% symmetry around the horizontal plane. This is vital for a TETRA base station located in the center of a city or industrial complex; it guarantees that users to the North receive exactly the same signal quality as users to the South.

3. Overcoming Passive Inter-Modulation (PIM)

In multi-channel TETRA trunking systems, multiple transmitters operate simultaneously through a single antenna. If the antenna has loose or mechanical joints, these signals can "mix" and create interference (PIM).

• Fully Welded Construction: The AC6-840 features fully welded internal junctions. By eliminating mechanical fasteners within the radiating elements, the antenna prevents the generation of interference products that could desensitize the base station's receivers. This ensures that even in high-traffic periods, the "noise floor" remains low and weak signals from distant handhelds can still be heard.

4. Polarization and Signal Alignment

TETRA handhelds and mobile vehicle radios almost exclusively use vertical whip antennas.

• Vertical Alignment: The AC6-840 is Vertically Polarized, ensuring a perfect 1:1 match with field equipment. Because the antenna maintains this polarization purity across the entire 806–870 MHz band, the "Capture Effect" is maximized. This means the base station can "grab" the signal from a low-power handheld radio even in the presence of background RF noise.

TETRA Deployment Checklist

• Tower Placement: To fully utilize the 6 dBd gain, mount the AC6-840 at the highest clear point on the mast. Avoid mounting it directly alongside the tower leg; use a stand-off bracket to ensure the tower structure doesn't "shadow" the 360-degree omni pattern.
• Lightning and Static Protection: Ensure the antenna is properly grounded via its mounting pipe. The 6063T6 aluminum and marine-grade stainless steel provide a low-resistance path to ground, draining static buildup that can occur during high-wind events.
• Cable Selection for 800 MHz: At 800 MHz, signal loss in coaxial cable is significant. For a standard 30-meter tower run, use LDF4-50A (1/2" Heliax) or better to ensure that the 400W transmitter power actually reaches the antenna radome.
• Connector Weatherproofing: Although the N-Female termination is enclosed at the bottom of the radome, always apply a layer of butyl rubber tape and electrical tape to the connection. This prevents "moisture breathing," which can cause VSWR spikes over time in high-humidity environments.