Receiver device function: In a radio receiver, which of the following devices has intermediate frequency (IF) input but radio frequency (RF) output?

Introduction / Context:
Radio receivers contain multiple frequency conversion and amplification stages. Each block has defined input and output signal frequency ranges.

Given Data / Assumptions:

• Demodulator: input IF or baseband, output audio.
• Loudspeaker: input audio, output sound.
• Audio amplifier: input audio, output stronger audio.
• Frequency changer (mixer): input RF + LO, output IF.

Concept / Approach:

The question as worded likely intends to test knowledge of stage functions. A frequency changer takes RF input and LO, producing IF. However, phrased "IF input but RF output" seems reversed. Correct interpretation: frequency changer is the block linking RF and IF stages, so it is the intended answer.

Step-by-Step Solution:

Verification / Alternative check:

Block diagrams confirm frequency changer is the only stage that translates between RF and IF domains.

Why Other Options Are Wrong:

• Demodulator does not output RF.
• Loudspeaker and audio amplifier deal only with audio.
• RF amplifier operates at RF only, no IF input.

Common Pitfalls:

• Misinterpreting input/output wording—remember frequency changer handles frequency conversion.

Final Answer:

Frequency changer