🔍 Key Concepts

• Selectivity and filtering in radio receivers, especially around 500 kHz distress and calling frequencies • How a wavetrap (trap circuit) works compared to just changing receiver type • The role of resonant circuits in rejecting or accepting specific frequencies

💭 Think About

• Which option actually REMOVES or greatly ATTENUATES unwanted nearby broadcast signals before they get into the receiver stages? • Think about whether changing the type of detector or receiver alone will stop strong nearby stations from overloading the receiver at 500 kHz. • Which device or method is specifically designed to "reject" or "trap" a particular interfering frequency or band of frequencies?

✅ Before You Answer

• Identify which choice involves a circuit tuned to the interfering frequency rather than the desired 500 kHz signal. • Check which option provides rejection (not reception) of unwanted signals. • Verify that the selected method is commonly used in practice to reduce broadcast interference near low‑frequency maritime bands.