hey i just want to give some update. I've tried to use AJ-SR04M as the driver for fish finder transducer and its work with pretty decent result
I know it have diffirent frequency but it still work. I think if we can make 200KHz with just same voltage level as AJ-SR04M it will work fine. I've tried the fish finder (not Aj-SR04M) too in deep ocean and it have about 40 m depth reading limit.
next week ill try with more accurate measurement. even tho that AJ-SR04M has 6.5 m limit and since sound move about 4.411 faster in the water so the limit also increase to about 20..m or so. and that enough for my project. I'll keep up next week.