When a continuous metallic shield is not present or is not grounded, entry for transmitting station lead-ins into a building is permitted by which method(s)?

When a continuous metallic shield is not present or is not grounded, entry for transmitting station lead-ins into a building is permitted by which method(s)?

• A. through a rigid noncombustible nonabsorbent insulating tube or bushing
• B. Any of the above
• C. through a drilled window pane
• D. through an opening provided for the purpose in which the entrance conductors are firmly secured so as to provide a clearance of at least 2 inches

Answer: (B)

When a continuous metallic shield is not present or not grounded, you must use approved penetrations that preserve isolation and safety for entering transmitting-leads. Each of the described methods provides a compliant path if it is implemented to spec: - Using a rigid noncombustible, nonabsorbent insulating tube or bushing creates an insulated channel for the conductors, so there’s no conductive contact with the shield or building structure and RF can’t easily leak along the path. - Carrying the lead-in through a drilled window pane is allowed only if the opening plus its securing arrangement maintain proper isolation, prevent movement that could cause arcing, and comply with fire and insulation requirements. - An opening designed specifically for entrance conductors, with the conductors firmly secured to provide a clearance of at least 2 inches, ensures a defined, nonconductive separation from surrounding metal to minimize RF leakage and arcing. All of these are acceptable as long as the installation meets the required insulation, securing, and clearance criteria, so any of the above methods may be used.

When a continuous metallic shield is not present or not grounded, you must use approved penetrations that preserve isolation and safety for entering transmitting-leads. Each of the described methods provides a compliant path if it is implemented to spec:

• Using a rigid noncombustible, nonabsorbent insulating tube or bushing creates an insulated channel for the conductors, so there’s no conductive contact with the shield or building structure and RF can’t easily leak along the path.

• Carrying the lead-in through a drilled window pane is allowed only if the opening plus its securing arrangement maintain proper isolation, prevent movement that could cause arcing, and comply with fire and insulation requirements.

• An opening designed specifically for entrance conductors, with the conductors firmly secured to provide a clearance of at least 2 inches, ensures a defined, nonconductive separation from surrounding metal to minimize RF leakage and arcing.

All of these are acceptable as long as the installation meets the required insulation, securing, and clearance criteria, so any of the above methods may be used.