*Question G4D04:
What does an S meter measure?*  

*Correct Answer is  C: Received signal strength*  

### AI Response: (may contain errors)  

An S meter is a device found on many amateur radio receivers that measures the strength of the received signal. Here's why the correct answer is "Received signal strength":

1. **Correct Answer: C - Received signal strength**
   - An S meter provides a visual indication of the strength of the incoming radio signal. It typically displays this strength on a scale from S1 to S9, with each S-unit representing a 6 dB increase in signal strength. Beyond S9, the meter often shows additional decibels over S9 (e.g., S9 + 20 dB).

2. **Why the other choices are incorrect:**
   - **A: Carrier suppression**
     - Carrier suppression refers to the reduction of the carrier signal in a modulated transmission, particularly in single sideband (SSB) transmissions. It is not something that an S meter measures.
   - **B: Impedance**
     - Impedance is a measure of resistance in an AC circuit, expressed in ohms. It is related to the matching of components in a radio system but is not measured by an S meter.
   - **D: Transmitter power output**
     - Transmitter power output is the amount of power a transmitter sends to the antenna. This is typically measured with a power meter, not an S meter.

In summary, the S meter is specifically designed to measure the strength of the signal being received by the radio, making "Received signal strength" the correct answer.