FISH FINDER MAJOR COMPONENTS

Take a minute to read this sectoin to get an idea, if you are new to fish finders, of the different components that comprise the many different models and styles of fishfinders. This can help you in the selection process if you know what these components do and their use. Like I said above, there is no need to buy an overpowered fish finder and waste your hard earned money.

The basic components of a fish radar system are a transmitter, receiver, transducer, and a feedback device, which in most cases is a display. In simple terms, an electrical impulse is initiated from the transmitter. It is converted to a soundwave and sent out into the water by the transducer. When the sound wave strikes an object (a fish or the floor of the body of water, that portion of the sound wave is bounced off the object back tword the boat depending on the composition size and shape of the object. This echo strikes the transducer which then converts it back into an electrical signal, amplifies by the reciever, processed and sent to the display in the form of a graphical representation.

The Display

The display shows a history of the received echoes. The user can make a number of adjustments to tailor the fish sonar display to his or her preference, such as senitivity, the depth range and chart speed. Displays use a variety of technologies, provide different resolutions and number of shades of gray or color. Each display is made up of a number of pixels, which are little square blocks that make up the images. The more pixels and shades of gray or color the better resolution and image clarity

What are pixels and why are they important to the display.
This is simple. Pixel is short for "picture element" It is a single dot or Small Square In The Case Of LCD screens that make up the whole of the screen. For instance you will see a screen resolution representation like 240x240, this means the display contains 240 pixels in either direction. 240 Across and 240 Down for a total of 57,600 pixels.

The number of pixels on a unit's screen determines how much detail it can show. Remember that pixels are arranged in columns and rows. The more pixels a screen has in each vertical column, the less depth each pixel represents and therefore the higher the resolution. If a screen has 100-pixels in each column and you search for fish on the 0- to 50-foot depth range, each pixel represents 6 inches of depth (50 feet divided by 100 pixels equals ½ foot per pixel). A picture made with 6-inch building blocks isn't going to have a lot of detail. Take a Bottom Line® model with 240 pixels in each vertical column, and each pixel represents about 2½ inches of depth. Smaller changes in the bottom contour and subtle details in the structure features spring into view, giving you, the angler, better information.

The number of pixels in each horizontal row determines how long information stay on the screen before it scrolls off. This is especially important for units to show side-by-side displays of different kinds of information. Wide-screens, such as the Bottom Line Tournament NCC 6300 and the Tournament 5100, allow information to stay on the display a normal length of time even when the screen is split into separate features.

Fish Targets
Echoes from fish within the beam will be shown on the display by illuminated pixels. What image appears on the display depends on a number of factors: the sensitivity setting on the fishfinder, the cone angle of the transducer, the speed of the boat, and the size, depth, speed and direction of the fish. A fish that is swimming directly beneath the boat, it will create a consistent echo that will cause a continuous line to appear on the display. A stationary fish caught in a narrow beam transducer appears as a single point on the screen as the boat passes above it, whereas under the same conditions the fish appears as an arch if a wide beam transducer is used.

A system called "Fish ID" is incorporated in Humminbird products to assist the angler by automatically recognizing the echo from the fish and displaying a "fish icon" above the point or arch on the display which triggered the fish detection. Additionally, with multi-beam transducer that transmits beneath the boat, as well as to either side, the Fish ID software can distinguish the location of the fish in reference to the boat and display the icon appropriately. A solid fish icon is displayed when the fish is beneath the boat and a outlined icon when it is detected on either side. Optionally, a fish alarm can sound to draw the angler’s attention to the fish as they are detected.

Fish Arches
Fish arching generally occurs when a wide sonar beam is used. This effect is due to the area covered by the sonar beam and the relative movement of the fish and boat. The sonar system measures the distance between the transducer and the fish target. This distance is greatest when the fish is at the edge of the coverage area, and at the minimum when the fish is directly below the transducer. Thus as the boat passes over the stationary fish the display first begins marking echoes at a certain depth and continues to mark and increasing shallower returns that peaks as the fish is directly beneath the boat. As the boat travels away from the fish the display continues the show progressively deeper echoes until the fish is not longer within the beam.

Transducer

The transducer is the part of the fish sonar that sends and receives the sound pulses. The active component in the transducer is commonly referred to as a crystal but actually is a piezoelectric ceramic material. The ceramic material takes the electric transmit signal and transforms it into a mechanical acoustic wave that travels in the water. When the acoustic wave strikes any discontinuity in the water a part of the signal is reflected back to the transducer and since the transducer is reversible (i.e. transforms an electric signal to acoustic signal and vice-versa), it converts that reflected signal back into an electric signal. This signal is sent to the receiver for processing and then on to the display for viewing. A sonar transducer must operate at the same frequency as the unit’s transmitter and receiver, which are also tuned to the same frequency, just as a radio is tuned to a given radio station. This means that a 200 KHz transducer cannot operate with sonar that operates at 50 or 455 KHz. It can only operate with a 200 KHz sonar. However, there are some sonar’s that are dual frequency (i.e. 200/455 or 50/200 KHz) and have appropriate transducers which contain either a single ceramic disk that has two operating frequencies or multiple elements inside the housing operating at different frequencies. This allows multiple applications with a single sonar unit.

Transom mount transducer
As the name implies, transom mount transducers are installed on the boat’s transom, directly in the water and typically sticking a little below the hull. Transom mounts are composed of plastic and tend to be less expensive than other transducers.

Transom mount transducers are recommended for planing hulls of less than 27 feet (8 meters), such as personal watercraft and powerboats with outboard, inboard-outboard and jet drives. They are not recommended for large or twin screw inboard boats because aerated water from the propeller reduces performance. They are also not recommended for operation at very high speeds.

Transom mounts adjust to transom angles from 3° – 16°. For angles greater than 16°, a tapered plastic, wood or metal shim will be needed. However, the transducer should be adjusted so it is angled slightly forward when the boat is in the water.

Thru-Hull Transducer
Thru-hull transducers are mounted through a hole drilled in the bottom of the boat and protrude directly into the water. This type of transducer generally provides the best performance.

Thru-hulls are recommended for displacement hulls and boats with straight-shaft inboard engines. You’ll also need a fairing block that allows the transducer to be mounted properly. Thru-hull transducers must be installed with a fairing to ensure proper alignment and a secure fit.

Thru-hull transducers must be positioned in front of the propeller, rudder, keel or anything else that may create turbulence. They must be mounted in a position that is always underwater and angled straight down.

In-Hull Transducer
In-hull (a.k.a. shoot-through) transducers are epoxied directly to the inside of the hull. These are only used in fiberglass hulls. In-hulls will not work with wooden aluminum, wood, or steel hulls, or in foam sandwich or hulls that have air pockets. Any wood, metal, or foam reinforcement must be removed from the inside of the hull.

With an in-hull transducer, the signal is transmitted and received through the hull of the boat. As a result, there is considerable loss of sonar performance.

In other words, you won’t be able to read as deep or detect fish as well with an in-hull transducer as with one that’s transom mounted or thru-hull mounted.

Fiberglass hulls are often reinforced in places for added strength. These cored areas contain balsa wood or structural foam, which are poor sound conductors. The transducer will need to be located where the fiberglass is solid and there are no air bubbles trapped in the fiberglass resin. You’ll also want to make sure that there is no coring, flotation material, or dead air space sandwiched between the inside skin and the outer skin of the hull.

Dual Frequency Fish Finder Transducer
Dual frequency should be used at sea and in the great lakes only. Use single frequency if you fish the great lakes under 200 feet and do not use a downrigger.

Single Frequency Fish Finder Transducer
Good for inland and shallow water where you want good fish target returns over the widest possible area.

Broadview and Dual Beam Fish Finder Transducer
The broadview transducer allows wide spread to the sides and down, many fisherman use a broadview or dual beam for a second finder or a second transducer by adding a transducer switch.

Reciever

The reciever takes the echoed sound wave that have struck the transducer on the return after coming in contact with something in teh water. The signal is analyzed and interpreted by the reciever and then sent off to the display.

Transmitter

The transmitter initiates the FishFinder pulse by sending a electronic signal to the transducer which is then sent out into the weater.