Allen-Bradley 1786-BNC ControlNet Coaxial Media Tap

Allen-Bradley 1786-BNC ControlNet Coaxial Media Tap

Configured for physical layer connection and drop signal distribution in ControlNet networks, the Allen-Bradley 1786-BNC (1786-BNC ControlNet Coaxial Media Tap) provides direct physical/electrical execution.

Hardware Specifications

ControlNet Coaxial Determinism & Network Integrity

In industrial ControlNet architectures using the Allen-Bradley 1786-BNC, deterministic data delivery depends strictly on physical layer signal integrity across the RG-6 coaxial trunk line. The media tap introduces a controlled attenuation drop without disturbing trunk impedance when nodes are connected or disconnected. Maintaining a deterministic network requires adherence to physical constraints, including the maximum limit of 48 nodes per segment and maintaining strict 75-ohm characteristic impedance across the entire cable run. Improper tap distribution or missing 75-ohm line terminators (1786-XT) causes high-frequency signal reflections, degrading the deterministic signal timing and generating frame errors across the backplane bus communication link.

Frequently Asked Questions

Q: Can a ControlNet node be disconnected from the 1786-BNC tap without interrupting overall network communication?

A: Yes, the 1786-BNC passive internal design allows node connection and removal via the drop line without disrupting the continuity of the main RG-6 coaxial trunk line.

Q: What is the minimum physical spacing requirement between adjacent 1786-BNC taps on a single trunk segment?

A: A minimum physical distance of 1 m must be maintained between adjacent taps along the RG-6 trunk cable to prevent impedance mismatches and destructive signal reflections.

Q: Is standard commercial RG-6 coaxial cable compatible with the 1786-BNC media tap?

A: No, standard commercial or TV RG-6 cable is not permitted. The physical layer requires quad-shielded ControlNet-rated coaxial cable, such as Allen-Bradley 1786-RG6, to maintain target noise immunity and signal impedance.

Field Installation Guidelines

1. Verify that both physical ends of the RG-6 coaxial trunk line are terminated with standard 75-ohm coaxial terminators (1786-XT) prior to energizing connected nodes.
2. Maintain a minimum separation distance of 1 m between consecutive 1786-BNC taps along the trunk segment to ensure signal reflection attenuation.
3. Route RG-6 coaxial trunk cabling through separate metal conduits or maintain at least 200 mm physical clearance from high-voltage power lines and variable frequency drive motor cables to reduce electromagnetic interference.
4. Ensure all BNC bayonet connectors are fully locked and mated to achieve the IP67 ingress protection rating. Inspect connections periodically in high-humidity or corrosive environments.