*Question E1A09:
[97.313(l)] Except in some parts of Alaska, what is the maximum power permitted on the 630-meter band?*  

*Correct Answer is  D: 5 watts EIRP (equivalent isotropic radiated power)*  

### AI Response: (may contain errors)  

On the 630-meter band, the FCC regulates the maximum power to ensure that amateur radio operations do not interfere with other services. The correct answer is:

**D: 5 watts EIRP (equivalent isotropic radiated power)**

### Explanation:

1. **Correct Answer: 5 watts EIRP**
   - **EIRP** stands for Equivalent Isotropic Radiated Power. It is a measure of the power radiated by an antenna as if it were an isotropic radiator (a theoretical antenna that radiates equally in all directions).
   - The FCC limits the power on the 630-meter band to 5 watts EIRP to minimize interference with other services and ensure efficient use of the spectrum.

2. **Why Other Choices Are Incorrect:**
   - **A: 50 watts PEP (peak envelope power)**
     - PEP refers to the maximum power level of a signal during a single RF cycle. This is not the correct measure for the 630-meter band, which is regulated by EIRP, not PEP.
   - **B: 100 watts PEP (peak envelope power)**
     - Similar to choice A, this is a PEP measurement and is not applicable to the 630-meter band, which is limited by EIRP.
   - **C: 1 watt EIRP (equivalent isotropic radiated power)**
     - While this is an EIRP measurement, it is below the maximum allowed limit. The correct limit is 5 watts EIRP, not 1 watt.

### Useful Formula:

To calculate EIRP, you can use the formula:  
$$
EIRP = P_T \times G_A
$$  
where:
- $P_T$ = transmitter power in watts
- $G_A$ = antenna gain (linear, not in dB)

This formula helps you understand how the power output and antenna gain contribute to the EIRP, which is the regulated limit for the 630-meter band.