When there is faint Doppler echo in noise, the system output is intermittent chaotic, and the Doppler shift can be obtained accurately by calculating the interval of chaotic state.
Call me when the fog set in. Sound regulation whistle, attend to echo sounding and start radar at an interval not more than 20 minutes.
下雾时要叫我，鸣放汽笛，动用测深仪，启动一次雷达不要超过20分钟。
3
Fog comes, call Captain at once. Began to keep on radar for detecting to the sea all round atr a interval of every 20 mins. Sounding by echo 52 fms. S/B. Fog sig started.