What term describes a narrow band jammer set to a given frequency?

The term that best describes a narrow band jammer set to a specific frequency is spot noise. Spot noise jamming is characterized by its ability to target a particular frequency with a focused beam of jamming, which makes it effective for disrupting communications or radar systems operating within that narrow band.

This approach allows for precise disruption, making it a common tactic in electronic warfare when the goal is to interfere with specific signals while minimizing the impact on adjacent frequencies. Spot noise jamming is useful in situations where the jamming needs to be as unobtrusive as possible to avoid detection or counter-jamming efforts.

In contrast, other types of jamming, like barrage noise or swept spot noise, involve broader bands of frequencies or sweeping across multiple frequencies, which do not fit the narrow focus described in the question. Therefore, spot noise is the most accurate descriptor for a jammer that operates strictly at a designated frequency.