This answer originated from a comment from @Mark

This is a ground issue.

Even though the ESC will work without a ground from the Arduino, to make the signal stable I needed to accompany the signal wire from the Arduino with a ground wire from the Arduino.

Per my example I took the disconnected ground from the ESC and connected it to the GND from the Arduino.

This answer originated from a comment by @Mark

This is a ground issue.

Even though the ESC will work without a ground from the Arduino, to make the signal stable I needed to accompany the signal wire from the Arduino with a ground wire from the Arduino.

Per my example I took the disconnected ground from the ESC and connected it to the GND from the Arduino.

This answer originated from a comment

This is a ground issue.

Even though the ESC will work without a ground from the Arduino, to make the signal stable I needed to accompany the signal wire from the Arduino with a ground wire from the Arduino.

Per my example I took the disconnected ground from the ESC and connected it to the GND from the Arduino.

This answer originated from a comment from @Mark

This is a ground issue.

Even though the ESC will work without a ground from the Arduino, to make the signal stable I needed to accompany the signal wire from the Arduino with a ground wire from the Arduino.

Per my example I took the disconnected ground from the ESC and connected it to the GND from the Arduino.