2.7 Coaxial Cable Termination for ICT Systems

Coaxial Cable in Modern ICT Buildings

Although balanced twisted-pair copper carries the majority of new data traffic in commercial structured cabling systems (SCS), coaxial cable remains a required skill for the BICSI Installer 2 Copper (INSTC) credential. Coax appears wherever radio-frequency (RF) signals must travel with controlled impedance and superior shielding: cable television and broadband drops, satellite and MATV headends, closed-circuit television (CCTV) camera links, some legacy Ethernet segments, and RF test paths. An INSTC installer must recognize coax types, prepare cable correctly, terminate with the proper connector system, and bond coax shields at the building entry without damaging the dielectric or compromising return loss.

Coax differs fundamentally from twisted-pair: a single center conductor is surrounded by a dielectric insulator, a metallic shield (braid, foil, or both), and an outer jacket. Signal quality depends on maintaining a consistent 75-ohm (or 50-ohm in some test/LAN applications) impedance along the entire path. Any nick in the center conductor, compression of the foam dielectric, or gap in shield continuity creates reflections that show up as pixelation, ingress noise, or failed sweep tests.

Coax Types Commonly Found in Buildings

RG-6 quad-shield or tri-shield constructions are typical in modern installs because additional foil and braid layers reduce electromagnetic interference (EMI) pickup—critical when coax shares cable trays with PoE bundles and fluorescent ballasts.

F-Connectors vs. BNC Connectors

Connector choice follows the equipment port and frequency requirements:

• F-connectors — Threaded or push-on interfaces dominate residential and commercial RF distribution (cable modem drops, splitters, amplifiers). Compression F-connectors are the professional standard in commercial work because they resist pull-out and maintain 360-degree shield contact.
• BNC connectors — Bayonet-twist coupling appears on analog and HD-SDI CCTV cameras, oscilloscope leads, and some legacy thin-Ethernet equipment. BNC terminations also use compression or crimp barrels, but the coupling mechanism differs from F-type hardware.

Regardless of connector family, the installer must match the connector to the exact cable series (RG-6 vs. RG-59) because bore diameter and dielectric recess dimensions differ. Using an RG-59 connector on RG-6 leaves an air gap that destroys impedance match.

Cable Preparation and Strip Lengths

Proper strip dimensions are manufacturer-specific, but INSTC candidates should internalize the three-zone prep model:

1. Outer jacket removal — Only the minimum jacket length required to seat the connector; avoid scoring the braid.
2. Braid and foil folding — Fold braid uniformly back over the jacket stub; do not cut braid strands unless the connector design requires it.
3. Dielectric trim — The foam or solid dielectric must protrude a controlled distance into the connector body without being crushed when the nut is tightened.

Typical RG-6 compression F-connector prep (verify against the connector manufacturer's template):

The most common field failure is dielectric damage: over-tightening, using dull strippers, or seating the connector with pliers crushes foam dielectric, permanently increasing capacitance and return loss. Use calibrated coax strippers with depth stops, and inspect every termination under good lighting before sealing outdoor enclosures.

Compression vs. Crimp Termination

Compression fittings use a single axial compression stroke to collapse a ferrule around the cable jacket and capture the braid. Advantages include:

• Consistent 360-degree shield engagement
• High pull strength suitable for aerial and riser drops
• Reduced risk of loose braid strands causing intermittent ingress

Crimp connectors rely on a radial crimp around the ferrule. They are faster and cheaper but more sensitive to operator technique. A misaligned crimp die can cut braid, fail to compress fully, or deform the center conductor. Many owner specifications now mandate compression-only terminations for any coax behind ceiling tiles or in tenant spaces.

After termination, verify shield continuity with a continuity tester or ohmmeter from connector shell to shell on a short jumper. For critical RF paths, a sweep test or return-loss measurement confirms impedance uniformity—especially after every connector in a long CCTV homerun.

Grounding Coax at Building Entry

Coax that enters from the point of demarcation, satellite dish, or CATV utility must be bonded to the telecommunications grounding busbar (TGB) or approved grounding electrode conductor path per NEC Article 800 and 820 (community antenna television and radio distribution). The outer shield can carry lightning surge energy; bonding limits potential difference between coax and other grounded systems.

Best practices at the entrance facility include:

• Install an approved coax grounding block or surge protector with a listed bonding conductor (often #10 or #12 AWG copper, per listing and AHJ).
• Keep the bonding conductor as short and straight as possible to minimize inductance.
• Ground the shield before the cable fans out to interior splitters so surge current does not propagate across the entire building.
• Coordinate with the utility provider on who owns the drop, grounding electrode, and demarc connector.

Failure to bond coax at entry is both a code violation and a common source of ground-loop hum on CCTV and hum bars on video displays.

When Coax Appears on INSTC vs. Twisted-Pair Work

The INSTC exam emphasizes copper ICT installation holistically, not only Category 6A data jacks. Expect coax tasks when:

• Extending a MATV/CATV backbone through a telecommunications room
• Homing CCTV cameras to a head-end switch or DVR in the same pathway as SCS cables
• Terminating coax at a media panel that also holds RJ-45 jacks
• Replacing damaged connectors on an existing RF drop during a renovation

Coax work does not replace twisted-pair competencies: Ethernet data channels still require pair-map compliance, NEXT/return-loss certification, and ANSI/TIA-568 administration. The installer must know which system they are serving—RF analog/digital video vs. packetized data—and apply the correct test instrument. Mixing 75 Ω coax plant with 100 Ω UTP expectations is a frequent exam trap.

Field Quality Checklist

Before closing a coax pathway or ceiling tile:

1. Connector series matches cable (RG-6 hardware on RG-6 cable).
2. Dielectric is intact, uncompressed, and correctly recessed.
3. Braid fully captured under the connector ferrule; no stray foil fragments.
4. Center conductor is centered and not bent.
5. Entry bonding block installed and connected to the TGB.
6. Labels identify circuit origin, destination, and service (e.g., CCTV-CAM-12).

Mastering coax termination protects signal integrity for services that tenants still depend on daily, even as fiber and twisted-pair dominate new construction.