*Question G1E10:
[97.101] Why should an amateur operator normally avoid transmitting on 14.100, 18.110, 21.150, 24.930 and 28.200 MHz?*  

*Correct Answer is  A: A system of propagation beacon stations operates on those frequencies*  

### AI Response: (may contain errors)  

The correct answer is that a system of propagation beacon stations operates on those frequencies. Here's why:

1. **Correct Answer Explanation (A):**
   - **Propagation Beacon Stations:** These frequencies are used by the International Beacon Project, which operates a network of propagation beacons. These beacons help amateur radio operators assess the current conditions of the ionosphere and determine which bands are open for communication. By listening to these beacons, operators can gauge the best frequencies to use for long-distance communication.

2. **Incorrect Choices:**
   - **Choice B (Automatic Digital Stations):** Automatic digital stations do not specifically operate on these frequencies. They typically use other parts of the amateur bands designated for digital modes.
   - **Choice C (Emergency Operations):** These frequencies are not set aside for emergency operations. Emergency communications usually have designated frequencies or bands, but they are not specifically these frequencies.
   - **Choice D (FCC Bulletins):** The FCC does not use these frequencies for bulletins. FCC bulletins are typically disseminated through other means and not on specific amateur radio frequencies.

3. **Useful Rules of Thumb:**
   - **Avoid Interference:** Always be aware of specific frequencies that are reserved for special purposes, like propagation beacons, to avoid causing interference.
   - **Check Band Plans:** Familiarize yourself with the band plans and any special allocations within the amateur bands to ensure compliance and optimal operation.

Understanding the purpose of these frequencies helps ensure that amateur radio operators use the spectrum efficiently and avoid interfering with important services like propagation beacons.