Final answer:
The USC-61 DMR component that amplifies RF signals in the 30-400MHz frequency range is the Amplifier Unit, which is essential for boosting signal strength for clear transmission and reception.
Step-by-step explanation:
The component from the USC-61 DMR that amplifies RF signals in the 30-400MHz frequency range is the Amplifier Unit. An amplifier's primary function in a radio system is to increase the power of a signal. It takes the weak RF signals that are within its operating frequency range—in this case, 30-400MHz—and boosts them so that they are strong enough for further processing and transmission.
This function is critical in communication systems where signals must travel long distances and have sufficient strength to be received clearly without loss of information. The components like mixer, power supply, and filter module have different roles. A mixer is used for frequency conversion, a power supply provides necessary electrical power to the system, and a filter module is responsible for suppressing unwanted frequencies and allowing the desired signal band to pass through. Therefore, the correct answer is a) Amplifier Unit.