Figuring out fish finders

When the world of electronics and computer chips evolved from pinball machines to PacMan, the move left a bunch of us in the dust.

Lordy, now the world has rushed ahead to gizmos with strange inames, like ipods and itunes, so it's doubtful I'll ever catch up.

The same thing could be said about fishing electronics — you know, sonar signals that arrive in color, GPS antennas chatting with satellites 11,000 miles above the walleyes and computer chips smaller than a Ritz cracker that hold detailed maps of more than 500 lakes or more.

These hi-tech advances have left a lot of wannabe anglers rowing with one oar. One of my fishing partners wants his sonar screen set to show the depth, plus little fishes moving right to left.

He can turn off that feature, but he thinks they're really fish. He doesn't realize the return signal could be something else.

Since the sonar can't think for itself, it shows every sonar echo as fish. He ought to go back to checking the depth with a rope and rock.

For almost 40 years now, ever since Carl Lowrance invented the little sonar box for anglers, we've been on a long learning curve.

All of which explains why a pair of Minnesotans, Bruce Samson and Bill Diedrich, continue to hold a series of all-day electronics seminars for anglers who want to know more than how to turn the danged things on.

Samson is a medical-doctor-turned-professional-walleye-angler and Diedrich is a math-teacher-turned-sonar-guru.

A few gems of sonar wisdom gathered from one of their seminars:

What is the sensitivity setting?

It's like the volume knob on a radio. For most conditions, the sensitivity should be as high as possible, 75 to 100 percent.

What is the sonar signal?

It is sound sent through water but measured by time and converted to distance. The signal is the shape of a cone. Sound travels through water at a speed of 1 mile per second.

Keep in mind the sonar reads the nearest object in the cone signal. If the sonar unit says the depth is 20 feet, that represents the shortest distance from the bottom target to the receiving transducer. This is important to know.


When you troll up or down a sharp drop-off, you most likely will not see fish because the return signal strikes the bottom first since it is the shortest distance.

If you do see fish on a slope or break, it is because those fish are high off the bottom and, thus, a closer target for the sonar signal.

What about pixel count?

Short answer: When looking at sonar units to purchase, buy the highest pixel count you can afford. If your sonar unit has a colorline feature, turn it on.

Chart speed?

Fast as possible.

Fish ID feature?

Turn it off.

Can you tell the size of a fish by the size of the return signal?

Don't count on it.


Because the size of the return signal depends on how the location of the fish target within the cone. On the other hand, if the return echo is large, it could come from a large fish.


It is the swim bladder in a fish that bounces the sonar signal. Big bladder, big fish.

If you see fish on the sonar screen, does that mean you'll catch 'em?

Silly question.

Ron Schara may be reached at ron@mnbound.com.

Schara's 250-page book, "Ron Schara's Minnesota Fishing Guide" (Tristan Outdoors; $19.95) is available by clicking here or by calling 888-755-3155.

Ron Schara's short feature, "The Outdoor Beat," airs at 7:55 a.m. ET Sundays on ESPN2. Click here to view this week's show descriptions.