*Question E1F01:
[97.305] On what frequencies are spread spectrum transmissions permitted?*  

*Correct Answer is  B: Only on amateur frequencies above 222 MHz*  

### AI Response: (may contain errors)  

Spread spectrum transmissions are a method of transmitting radio signals by spreading the signal over a wider bandwidth than the minimum necessary to transmit the information. In amateur radio, these transmissions are regulated by the FCC.

1. **Why the correct answer is correct:**
   - The correct answer is **B: Only on amateur frequencies above 222 MHz**. According to FCC regulations, spread spectrum operations are permitted only on amateur bands above 222 MHz. This includes frequencies in the 1.2 GHz band and higher, where spread spectrum techniques can be effectively utilized.

2. **Why the other choices are incorrect:**
   - **A: Only on amateur frequencies above 50 MHz**: This is incorrect because spread spectrum is not allowed below 222 MHz.
   - **C: Only on amateur frequencies above 420 MHz**: This is also incorrect as it is too restrictive; spread spectrum is allowed on all frequencies above 222 MHz, not just above 420 MHz.
   - **D: Only on amateur frequencies above 144 MHz**: This is incorrect for the same reason as option A; spread spectrum is not permitted below 222 MHz.

3. **Useful rules of thumb:**
   - Remember that spread spectrum is primarily used in higher frequency bands due to the characteristics of the technology and the regulations set by the FCC.
   - Always check the latest FCC rules and regulations for any updates regarding frequency allocations and permitted modes of operation.

This understanding is crucial for the Extra Class exam and for practical amateur radio operations.