I have a hummingbird depth finder on my bass tracker.  The transducer is located on the trolling motor.  I might upgrade it later on but so far have just used it to determine different depths.  My question is when you see structure under the water on your depth finder where is it actually located under the water?  Is it a couple of feet in front of the boat or what?

A good rule of thumb is the depth of the water is the size of the circle the d.f. will show on the screen. Say you're in 10ft. of water, the "cone" of the transducer will cover roughly a 10ft. circle. The d.f. will scroll from right to left on the screen, so the information you see on the far right is the most recent info and is in the cone of the transducer at that moment.

Depends on the model, and the frequency you are running. I run a dual beam, 200 and 83 kHz. The 83 kHz beam is 60°, and would therefore be close to as big around as deep, but a little bigger. But I go with the 200 kHz narrow, 20° beam for better definition.

Here is the site for the online manuals.  You can probably find your model on the list to see the specs for what beams yours uses.

It is determined by the cone angle and depth. All this assumes the transducer is level. Best way to tell is to get in 20-30 ft of water and drop a large spoon straight down. Ideally you'll see the spoon go up and down if you jig it. If you don't see it turn your trolling motor until you do and you know which direction it's pointing.

Awe Man!!!  Sorry, I didn't post the link to the online manuals....

Here it is: http://www.humminbird.com/support/FAQ.aspx?faqid=72

As I remember Don Iovino said in his book the  structure would be 6 to 8 feet behind the transducer at slow boat speeds. The deeper the water and faster the boat speed puts the structure farther back.

Both Humminbird and Lowrance (probably some others, too) have some version of a real time feedback.  On my 383c, its to the left of the graph view.  I rely on this more than the history, especially when fishing vertically.  I can see my bait, and it rises on the screen as I lift up.  Its pretty fast.  For this technique, I have the graph set to 200 kHz, and ping speed turned up to max.

J Francho, every model of LCR sonar units I have seen or heard of scroll from right to left and the RTS (real time sonar) is on the right. History is everything left of the first vertical column of pixels on units without RTS.

I meant that the other way around, LOL. Left...Right....does anyone really know what's what?

Just kidding there. Thanks for the correction, Wayne. Yes, mine is on the RIGHT!

:-[ :-[ :-[

This is a little dark, but that thin strip on the right is the RTS. Obviously, nothing going on here when the photo was taken. I want to try and get more pics of the sonar when I'm out fishing. Just seems like I should be fishing, not shooting.

To see a RTS, just look at the picture advertisements for any LCR unit on-line or in a catalog such as BPS. The link is for a HB, the Lowrance RTS is not quite as wide.

http://www.basspro.com/webapp/wcs/stores/servlet/SceneSevenDisplay?catalogId=10001&storeId=10151&langId=-1&productId=-52575&productPartNumber=52575&scene7Path=BassPro%2f92847%3flayer%3dcomp%26wid%3d500%26hei%3d500%26fmt%3djpeg%26qlt%3d100%2c0%26op_sharpen%3d0%26resMode%3dnorm%26op_usm%3d1.0%2c1.0%2c0.0%2c0&sourceName=images2%2f92500%2f92847.jpg&type=0&linkEnabled=false