Why is the radar image shifting back and forth by 1°?

This condition usually occurs in the Furuno scanners but is not restricted solely to Furuno products. It is typically a result of the Heading Flash (HF) occurring very close to the rising edge of a Bearing Pulse (BP).

There is a small metallic sensor on the Scanner’s main gear; this sensor causes the Heading Flash to occur. The sensor’s position can be adjusted ~±5°. Reference the radar’s manual to verify the location of the Heading Flash Sensor. Loosen the screws to this sensor and reposition it. This will change the rising edge relationship between the HF and BP and eliminate the radar image jitter.