*Question G4A01:
What is the purpose of the notch filter found on many HF transceivers?*  

*Correct Answer is  B: To reduce interference from carriers in the receiver passband*  

### AI Response: (may contain errors)  

The purpose of a notch filter on many HF transceivers is to reduce interference from unwanted carriers within the receiver's passband. Let's break down why this is the correct answer and why the other choices are incorrect:

1. **Correct Answer: B - To reduce interference from carriers in the receiver passband**
   - A notch filter is designed to attenuate or "notch out" specific frequencies. In the context of HF transceivers, it is used to reduce or eliminate interference from unwanted carriers or signals that fall within the passband of the receiver. This helps improve the clarity of the desired signal by removing the interfering tone or carrier.

2. **Why the other choices are incorrect:**
   - **A: To restrict the transmitter voice bandwidth**
     - This is incorrect because a notch filter is not used to limit the bandwidth of a transmitted signal. Instead, it is used in the receiver to remove specific interfering signals.
   - **C: To eliminate receiver interference from impulse noise sources**
     - Impulse noise is typically broadband and not confined to a narrow frequency range. A notch filter is not effective against such wideband noise; instead, noise blankers or other noise reduction techniques are used.
   - **D: To remove interfering splatter generated by signals on adjacent frequencies**
     - Splatter from adjacent frequencies is usually addressed by using filters with appropriate bandwidth in the receiver's front end, not by a notch filter. A notch filter targets specific frequencies within the passband, not adjacent channel interference.

In summary, a notch filter is a valuable tool in reducing interference from specific, narrowband signals within the receiver's passband, enhancing the listening experience by removing unwanted tones or carriers.