I am looking for help with my new HDS. I installed it last week and have had it out 1 time. I installed the structure scan transducer that came with the unit and I noticed the sonar screen does not work. The side imaging screen works, however there looks to be a little "noise in the water column. Do I have to also install the transducer that came with the HDS for the sonar to work? Also, will this unit "down image"? Thanks for any help you can give.