Within how many inches of the RF line entrance should the PBB be located?

• A. Within 24 inches
• B. Within 12 inches
• C. Within 36 inches
• D. Within 48 inches

Answer: (A)

Keeping the PBB close to the RF line entrance is about creating a short, low-impedance path for RF grounding and shielding as the line enters the building. By placing the PBB within 24 inches, you minimize the length of exposed, unbonded cable and reduce the chance that RF currents will seek alternate, less controlled paths along conduits or equipment housings. This proximity helps maintain shielding integrity at the entry point and keeps the bond between the incoming line, the coax shield, and the facility grounding system tight and predictable.

The maximum distance defined is 24 inches, which sets the limit for proper placement; placing farther away would extend the path that RF currents could take before getting properly bonded, increasing potential interference and safety concerns. A shorter distance, such as 12 inches, would still meet the requirement, but the guideline specifies 24 inches as the upper bound.