Transmitter serial current: A transmitter's serial current contains which of the following frequency components?

Introduction / Context:
Transmitters convert audio or baseband signals into modulated radio frequency (RF) signals for transmission through antennas. The current in the transmitting antenna is primarily at the radio frequency carrier and its sidebands.

Given Data / Assumptions:

• Audio signal is used as modulating input.
• Carrier frequency is at RF (kilohertz to megahertz or higher).
• Output current flows through the antenna.

Concept / Approach:

After modulation, the transmitted signal is a high-frequency RF wave carrying audio information. Thus, the transmitter current contains RF energy, not baseband audio directly.

Step-by-Step Solution:

Verification / Alternative check:

Textbook transmitter models confirm antenna current is RF current.

Why Other Options Are Wrong:

• Carrier frequencies: incomplete, as modulation adds sidebands.
• Audio frequencies: never appear directly in antenna current.
• None of the above: false, since RF is present.
• Both carrier and audio: misleading, as audio is not present directly.

Common Pitfalls:

• Thinking audio current flows in antenna—it does not.

Final Answer:

Radio frequencies