During a utility locate, which frequency choice helps reduce coupling to adjacent lines?

• A. Highest frequency
• B. Mid frequency
• C. Any frequency
• D. Lowest frequency

Answer: (D)

Using the lowest practical frequency helps reduce coupling to adjacent lines because the signal changes more slowly at lower frequencies. When a transmitter sends a signal into a buried utility, nearby conductors can pick it up through mutual induction and capacitive coupling. Higher frequencies produce quicker, stronger field changes, which nearby lines respond to more readily, increasing cross-talk and potential interference. By choosing the lowest frequency that still allows reliable detection, you minimize these unintended interactions with adjacent utilities while still enabling you to trace the target line. In practice, you balance detectability with minimizing coupling, but the principle remains: lower frequencies curb coupling to nearby lines.