*Question G1C11:
[97.313] What measurement is specified by FCC rules that regulate maximum power?*  

*Correct Answer is  D: PEP output from the transmitter*  

### AI Response: (may contain errors)  

The correct answer is: **D: PEP output from the transmitter**

1. **Why the correct answer is correct:**

   - The FCC specifies that the maximum power limit for amateur radio transmissions is based on the Peak Envelope Power (PEP) output from the transmitter. PEP is the highest power level in a single RF cycle during a modulation envelope. It is a crucial measurement because it reflects the maximum power the transmitter can deliver to the antenna system during normal operation.

2. **Why the other choices are incorrect:**

   - **A: RMS output from the transmitter**  
     RMS (Root Mean Square) power is not used by the FCC to regulate maximum power for amateur radio. RMS is more commonly used in AC power calculations but does not accurately represent the peak power levels in RF transmissions.

   - **B: RMS input to the antenna**  
     Similar to choice A, RMS input to the antenna is not a measurement used by the FCC for power regulation. The focus is on the transmitter's output, not the input to the antenna.

   - **C: PEP input to the antenna**  
     While PEP is the correct type of power measurement, the FCC regulation specifies the PEP output from the transmitter, not the input to the antenna. The input to the antenna could be affected by losses in the transmission line, which is not the focus of the regulation.

3. **Useful formulas or rules of thumb:**

   - **PEP Calculation:**  
     PEP is calculated as the maximum instantaneous power during one RF cycle. For a sinusoidal waveform, it can be related to RMS power by:  
     $$ PEP = 2 \times (\text{RMS Power}) $$  
     This formula shows that PEP is typically higher than RMS power, which is why it is used to ensure transmitters do not exceed power limits during peak operation.

Understanding PEP and its role in FCC regulations is essential for ensuring compliance with power limits in amateur radio operations.