Medium Frequencies are described as having what characteristics?

• A. Outside the power frequency interference band with limited coupling to unwanted lines
• B. Inside the power frequency interference band with strong coupling to unwanted lines
• C. Only useful for long-distance applications
• D. Cannot be used with induction

Answer: (A)

Focusing on a frequency range that sits above the typical power-line noise, medium frequencies are advantageous because they avoid the strong interference from the 50/60 Hz power supply and its harmonics. This means there’s less energy coupling into and from nearby lines, giving cleaner measurements when locating buried facilities. In other words, signals at these frequencies are less likely to be overwhelmed by power-line hum, which improves the reliability of detection and reduces false readings caused by incidental coupling to unwanted lines. The idea that medium frequencies must stay inside the power-frequency band or can’t be used with induction isn’t accurate; these frequencies actually strike a practical balance, working well with induction methods and offering better signal-to-noise than bands dominated by power-line interference.