Thread: Help!! Understanding My Electronics

Need some help. The pictures with the fish symbols are from my Garmin up front with the trolling motor. Question? Are the fish in front of me, behind me or what? And where do I need to cast. My trolling motor is a Terrova with spot lock. The other pictures are from my Lowrance at the rear fo the boat; and I ask the same questions. Also how can I determine "bait fish"??

mj

Originally Posted by mbjmbj50

Need some help. The pictures with the fish symbols are from my Garmin up front with the trolling motor. Question? Are the fish in front of me, behind me or what? And where do I need to cast. My trolling motor is a Terrova with spot lock. The other pictures are from my Lowrance at the rear fo the boat; and I ask the same questions. Also how can I determine "bait fish"??

mj

With 2D sonar you are reading a cone straight down from the transducer. The size of which depends on the depth of the water, the deeper the water, the bigger the cone. Only if the boat is moving, will returns on the left of the screen been behind you, if moving forward.

The left side of the screen is history, and the right side is closer to real time, or what is under the transducer right now. The vertical bar on the far right of your Garmin is called the A-scope and works similarly to a flasher, or a real time sonar. The number at the bottom of this is the diameter of the sonar cone at that depth, I can't make it out in your picture but it is there. If you turn the sensitivity up and the scroll speed to fast, you will be able to see your jig on the graph and all of what I just said will start to make more sense.

Thanks. What would you suggest the sensitive's be turned too or turn up to high setting.

Originally Posted by mbjmbj50

Thanks. What would you suggest the sensitive's be turned too or turn up to high setting.

Depends on what you are trying to do.

If you are "sharpshooting" or vertical fishing with a spoon or jig and want to see where your lure is in relation to the fish, high sensitivity is necessary. I usually have mine set on auto-high.

Once you get it dialed in, it's almost like a video game. Not livescope but still pretty good, as long as you can keep the boat in one spot.

Big help. Thanks!

Originally Posted by mbjmbj50

Thanks. What would you suggest the sensitive's be turned too or turn up to high setting.

Generally it's best to turn the sensitivity up to max & then slowly turn it down until you get the best image .... clear & not a lot of surface clutter.

How big the cone circle is on the bottom is determined by the cone angle of your unit. A 20deg cone will give you a circle on the bottom that is about 1/3 as wide as the depth, whereas a 60deg cone will give you a circle as wide as the water depth.

Baitfish schools generally show up on 2d sonar as a "blob", much like what's shown in the bottom pics. You might want to turn down the sensitivity on the Lowrance, as it looks like you have surface clutter in the first 4ft of depth. Not that big a deal in 14fow, but it looks to also be picking up a lot of excess clutter image at depth. If you were not moving at the time, those clutter lines could be debris or something (possibly your jig or sinker) that is inside the stationary cone.

You also have to remember that the cone angle of 2d sonar is basically like this : /\ .... so anything showing on screen has to be INSIDE that cone or just barely outside of it, and there's really no way to tell "where" they are in relation to the inside of the cone (other than how far away they are from the transducer) They may or may not be as deep as the screen says. Remember -- your unit is translating a 3d cone shaped ping onto a 2d flat screen.

Thanks. Makes a lot of sense. Not sure how to adjust the cone angle unless this is something that happens when out on the water. Now I've got a better idea of how the cone works.

Cone angle cannot be adjusted only changed by the frequency of the unit and transducer 200khz is narrower and 80khz is wider. So to cover more area with 2D select the lower frequency but remember since you are covering more area the fish you do see will be further from the transducer and no way to know which direction unless you are moving. For vertical presentations use the narrowest so the fish you do see will be closer to the transducer still no clue of direction. .

Yeah, the cone angle is "set" in the transducer, though some units may have settings where you can switch from one angle to another.

Check this out for a better understanding of the coverage area of 2d sonar cone :




And like Bricks says ... you don't really have any idea of the direction of the fish showing on the screen. The transducer can only pick up the object within the cone (& maybe a little outside of it) and it can only tell you how far away the object is from the transducer & NOT always the actual depth of the object.