Thanks for all these videos but my eyes just glaze over. I do not understand any of this. Frequencies, band widths etc. What the hell? For dummies please.
Forget about all the hype and electronic stuff. What you only want to know is where you are on the river and how much water is between you the bottom. Do you have friends that fish that could show you the basics? Is there an outdoor store near you like Bass Pro, Outdoor Man, Cabalas, or so? Go on a slow day and tell the sales rep in the fish finder department what you want is the basic model with the largest screen that will do it. If you are lucky the rep will spend some time on one of the demo models showing what they will do. This will give you an idea what you are getting into. Now you have that much knowledge starting looking around for a deal. Fishermen are nuts and are constantly upgrading to the latest and greatest. May find a deal on a used one at a big savings. Also if buying new ask if there is a discontinued model that is in stock after it was replaced with an upgraded model with even more un-needed bells and whistles. Most all of them will give you the ability to shift between chart plotter and depth finder or even better have a split screen display to see both at once and an alarm feature that can be set to let you know when you are getting into shallow water.
Remember that the depth finder isn't telling you about some underwater obstruction that is ahead of you, by the time the alarm goes off you have probably already hit it. That's where the chart function at least shows what to expect and give you time to slow down for known sand bars, etc.