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Lowrance Sonar Tutorial
Courtesy of Lowrance South Africa
Introduction
In the late 1950's, Carl Lowrance and his sons Arlen and Darrell began scuba diving to observe fish and their habits. This research, substantiated by local and federal government studies, found that about 90 percent of the fish congregated in 10 percent of the water on inland lakes. As environmental conditions changed, the fish would move to more favorable areas. Their dives confirmed that most species of fish are affected by underwater structure (such as trees, weeds, rocks, and drop-offs), temperature, current, sunlight and wind. These and other factors also influence the location of food (baitfish, algae and plankton). Together, these factors create conditions that cause frequent relocation of fish populations.
During this time, a few people were using large, cumbersome sonar units on fishing boats. Working at low frequencies, these units used vacuum tubes which required car batteries to keep them running. Although they would show a satisfactory bottom signal and large schools of fish, they couldn’t show individual fish. Carl and his sons began to conceptualise a compact, battery operated sonar that could detect individual fish. After years of research, development, struggle and simple hard work, a sonar unit was produced that changed the fishing world forever.
Actual Sonar Readings
Lowrance Lcx16ci - Sonar Recording - Sonar Viewer Application
Lowrance Lcx16ci - Wreck Recording- Sonar Viewer Application
Screen Interpretation: The screen below shows a wreck close to a reef. It has been lying there for several years but is still in good shape. It is not very deep (54') but it often provides shelter for fish like Pollocks as you would expect. On the day it was recorded there was a buoy on it probably attached to a lobster trap. The LCX16ci detects precisely the thin rope (1) from the buoy, the wreck itself (2) with its hull lying upside down clearly separated from the bottom by the ColorLine, the large fish in the « pool » of the wreck (3) which protects them from the tide and the little baitfish circling around it (4). There is a heavy « surface clutter » (5) due to the current and the plankton causing surface disturbance.
On the left of the main body of the wreck you can see a darker structure (6) that the unit is detecting and displaying in red thus indicating a much harder part of the target. This is actually the rear of the boat with much more metallic pieces coming out stronger than the wooden hull. On the wreck you can see some weeds as well as around the metallic structure in purple color. The unit's setting was Sensitivity 96%, ColorLine 80%, SCC off and ASP low. This is why we can see so many little echoes caused by tide bubbles, sand, weeds in suspension, fish and current disturbance. Notice that the unit is cutting through that with ease showing only the most useful information to the discerning angler.
A close up interpretation shows how much you can get from a top class fishfinder. The « cloud » extending behind the line in (1) is the echo created by the vibration of the line against the tide current. This explains why there wasn't many fish on the wreck and why fish can be spooked by anchor rope or thick fishing line. The amount of information revealed by the Lowrance LCX16ci is simply outstanding.
Installation of FishFinders
Please note that the following points have to be adhered to, when installing a fishfinder.
Reason: The transducer cable can pick up the sparks from the motor and this is shown as noise on the screen.
Install the cable inside some kind of conduit (i.e. a split fuel line or something similar)
Reason: It is important to protect the cable. If the cable gets just a little “nick” moisture will come in. Initially the transducer might go intermittently faulty, but after a while the moisture will have “walked” along the cable into the transducer. This cannot be repaired, so it is important to prevent the cable from being damaged.
The transducer cable must not hang loose.
Reason: A loose cable can easily get caught in something and be pulled thereby damaging the cable and the transducer.
Do not cut the transducer cable.
Reason: Inside the cable are many tiny strands of wire. It is virtually impossible to connect each wire again, which is necessary for the best reception.
Wire the powercable directly to the battery instead of to a switchpanel.
Reason: To prevent noise from other electrical installations.
When installing a ratchet-type transducer (large “Skimmer”) on a beach-launching Ski Boat, the little ratchet-rings must be removed.
Reason: When the boat hits the beach the bracket will get damaged if the ratchet is not removed.
Make sure the terminals are clean.
Reason: The battery is an integral part of the motor’s voltage system and clean terminals form part of this. Clean terminals are an extra “fuse”.
Be sure to fit the in-line fuse.
Reason: If the motor’s voltage “spike”, over-voltage can damage the unit.
When installing a transducer inside the hull make sure that there is no air in the area, where the transducer is mounted.
Reason: A transducer can read through fiberglass etc, but not through air. To find the best place to install a transducer do the following test:
- Hold the transducer by hand over the side of the boat and see what type of reading you get on the sonar;
- Put the transducer inside a Checkers-type plastic bag filled with water. Move this around inside the boat. The bag will take the shape of the boat. Install the transducer at the spot, where the reading inside is as close to the reading outside as possible.
Make sure the angle of the transducer is correct, when installing it.
Reason: The transducer is a transmitter and receiver in one, so it has to “catch” the sound-signals being bounced off the bottom. If the angle is too big, the sound-signals will bounce off the bottom in the opposite direction. Remember that the boat is not sitting on the trailer in your driveway the same way as it is sitting on the water.
Read the manufacturer’s installation instructions.
If in doubt - ask.
It is therefore very obvious why "pixel count" is critically important to any fishfinder's ability to display detail, especially when targets are schooled tightly, and let's face it: if an angler doesn't see a fish, he's probably less likely to catch it!
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Tags: Lowrance, Jetski Fishing, Jetski
