Streaks or spiral lines that sometimes show up

​If they appear intermittently and then go away, it is most likely radar interference from other vessels or perhaps even a second radar aboard your own boat. Furuno radars offer several levels of interference rejection, or "IR". IR is usually selectable from a menu setting. Start by applying the first level of IR and see if the interference stops. Even if higher levels of IR are necessary, you will note very little degradation of your radar picture. CAUTION: Interference Rejection may suppress certain very weak targets and/or radar signals from RACON buoys.