Which frequency is not listed among the potential DF monitoring frequencies in the material?

• A. 121.5 MHz
• B. 156.525 MHz
• C. 243 MHz
• D. 400 MHz

Answer: (D)

Direction finding (DF) monitoring focuses on tuning to the standard distress and emergency beacon channels so you can locate transmissions that indicate a SAR situation. The common frequencies monitored in this context are 121.5 MHz, 156.525 MHz, and 243 MHz, which are internationally recognized for search-and-rescue beacons. These bands are chosen because they are widely used by distress signals and have long-standing procedures for interception and homing. The 400 MHz range, however, isn’t part of that distress-beacon set; it sits outside the established DF monitoring frequencies for SAR use. So 400 MHz is not listed among the potential DF monitoring frequencies.