Greg
You are right about Dr. Halfen. He is very knowledgeable about our units and has a way of explaining it so you can understand. I don't know if it's politically correct or not, but I have posted links to his
website as he has several tutorials on using the HB products there. He also has many seminars posted on YouTube. I have learned a lot from them.
I do understand the 83/200kHz concept. You bring up another interesting use by rotating the transducer. I'll have to try that after the 14" of ice melt on my lake.
Mike