*Question G2E14:
What could be wrong if you cannot decode an RTTY or other FSK signal even though it is apparently tuned in properly?*  

*Correct Answer is  D: All these choices are correct*  

### AI Response: (may contain errors)  

To decode an RTTY (Radio Teletype) or other FSK (Frequency Shift Keying) signal properly, several factors must be correctly set. Let's explore why each choice is relevant:

1. **The mark and space frequencies may be reversed (Choice A):**  
   - RTTY signals use two frequencies: mark and space. If these are reversed, the decoder will interpret the signal incorrectly, leading to garbled output.

2. **You may have selected the wrong baud rate (Choice B):**  
   - The baud rate is the speed at which the signal is transmitted. If your equipment is set to a different baud rate than the signal, it will not decode properly. Common RTTY baud rates are 45.45 and 75 baud.

3. **You may be listening on the wrong sideband (Choice C):**  
   - RTTY signals are typically transmitted using a specific sideband (usually LSB for HF). If you are tuned to the wrong sideband, the signal will not decode correctly.

4. **All these choices are correct (Choice D):**  
   - Since any of the above issues can prevent proper decoding, the correct answer is that all these choices are correct.

In summary, each of the individual issues (A, B, and C) can independently cause problems with decoding an RTTY or FSK signal. Therefore, the correct answer is D: All these choices are correct.