Re: fishfinder/ sonar help??
it's ok, here's something that will greatly enhance your understanding of the fishfinder screen:
Only the far right-hand column of pixels shows what's under you right now...everything else is history.
Assuming a standard 20? cone angle, a lit pixel on your display represents an object that is somewhere inside a circle centered directly under the 'ducer, with a diameter about 1/3 its depth. In other words, an object shown at 30-foot depth is somewhere within 5 feet of your stern; it might be forward, aft, to port or starboard, or directly underneath.
Remember that the object was under your transom when it first appeared on the screen. As the image scrolls to the left, it's position is getting further behind you if you're moving forward.
If you're anchored in dead calm water, then a stationary object will draw a straight line across the screen. Try it with a 1oz lead casting spoon, or an anchor or something.
Also, the fishfinder will pick the strongest echo return, and display it as the bottom. But, it shows the shallowest bottom that it can see. Other words, say you're holding over a slope, with 25 feet of water off your starboard side and 30 feet to port. The screen will show the depth as 25 feet; any fish holding at 28 or 29 feet won't show up. That's how come you can catch fish on the bottom, even though they don't appear on the fishfinder.
One final word: turn off the "fish ID" feature and learn to interpret the echo signals for yourself. You'll soon be able to distinguish between a school of baitfish and a tree, or between a striped bass feeding frenzy and a shrubbery. I can't tell the difference between bass and catfish on the screen, but I can distinguish carp and gar from bass and cats.
Note: "diameter of 1/3 the depth" is a general rule of thumb for a 20? cone angle -- the actual diameter of the circle is "depth times the tangent of the cone angle". Also note that a fishfinder will detect objects outside the cone, and the area of detection gets bigger as you increase the sensitivity setting. But "1/3 the depth" is a good easy way to think of it.
!!!!!!!!!!!!!!!!!!!!!
wait a sec, I think I just figured out what your question really is...to the casual observer, the part of the transducer that's pointing back appears to be the "business end" where the signal is sent and received, BUT, that's not the case. Actually, the part pointing straight down is where the transmitter & receiver are aimed at. I had the same misconception the first time I installed one a those "puck" style 'ducers.
