Fish Finders And Frequencies

The image you see on a fish finder screen is already history. If you use the bottom alarm when you drive, you will probably already be stuck on the bottom when it pipes unless you drive in only a few knops speed. The traditional fish finder is definetely no search tool for shallows. It is best suited as a fish finder or for help when setting out nets, pots etc. and when searching for a suitable anchor place. For a sports fisherman a fish finder is a very useful tool to find the right depth for fishing, to see the fish, to find different temperature layers in the water and to have an image of the bottom conditions, that means whether the seafloor is soft or hard.

The images can be rolled back and forth in different speeds, so that they are adapted to the boats speed. When the image is starting to be visible in the right corner of the screen, it is the history under the transducer for one second you see, after approx. 10 seconds the whole screen is filled with information.

 

But it has to be said that most fish finders also can display a so called truetime-column in the right corner that tells the exact depth in truetime. Echo sounders sends out their signals on different frequencies, and for the simplest fish finders 200 kHz is the most common. This gives an image which is easy to read and right depth. Some echo sounders can be adjusted to 50 kHz transducer frequency and one will then have a bigger coverage under the water. If one has both frequencies on he can start the search at 50 kHz when searching for a shallow spot and then change to 200 kHz to get a clearer picture. The fish is easier to find with a 200 kHz and schools of fish can be seen as separate units on the screen on this frequency.

 

Another important factor is the soundwave gain in Watt. In the brocures one find two different gains, "RMS" and "peak to peak". The first mentioned is the most important when comparing different fish finders. "RMS" is the "raw" strength with an echo sounder, and here it can be sufficient with 150 to 200 Watt for the black/white fish finders to reach down to 300 feet. If one has a gain of 500 Watt, one should manage to reach 100 feet, and even in high speed the bottom should be displayed on the screen if the transducer is correctly placed. The size of the screen should be at least 4", preferably 5" if the screeen should display other information too., i.e. setting up an truetime bar at the corner besides the bottom image, or if one will show the bottom with both 200 kHz and 50 kHz at the same time.

 

Take a look at Humminbird Finder instruments as well as Fishfinder Garmin, Eagle and Fishfinder Lowrance