Getting the Most out of your Lowrance DSI Unit

[Fishton]

Contrast and Surface Clarity:

Unlike conventional 200/83kHz sonar that has the old traditional sensitivity and Colorline control, the DSI merely has 'Adjust' (Contrast in %).  Now if you were to head out with your unit fresh out of the box and you turned the unit on in 30ft of water or more, and you immediately passed over a great big submerged tree while drifting over it with a light breeze pushing you – you will be absolutely blown away by what you see on the screen.

But! ... If you are in shallow water you will be very disappointed on the default settings, especially on a trolling motor mount, because the screen will appear to be very cluttered.  And when you try turning the contrast down to eliminate this clutter, you will lose ALL definition and render the unit useless and leave you wanting to get your money back.  Don't feel bad, first time Porsche owners experience the same buyer's remorse, until they learn the old trick of 'easy in and hard out'.

So what is the trick to 'easy in and hard out' with a DSI?  Simple ... 800kHz and increasing the Surface Clarity.  This feature plays a significant part in maintaining a strong definition as well as contrast while reducing clutter at the same time.

Default setting is Low.  If you are going to be fishing >50ft you could actually set it to Off.  But as you start moving into the <15ft depth you will need to change to Low or even Medium depending on water conditions.  And for very shallow conditions – High.  But this is not all that you can do to sharpen your image up ... Frequency.



Frequency:

Default frequency is 455kHz, but it does not like very shallow water.  Select the 800kHz which will allow you to go shallower maintaining a higher spatial resolution as well as contrast.  Alternatively select the split screen dual frequency view.  This will give you the wider 55° coverage area of the 455kHz, as well as the sharp high resolution of the 800kHz but with a smaller 30° coverage area.  Play around with your contrast in these individual frequencies around the 60% margin.



Transducer installation:

The installation of the transducer is also going to play a big role in the quality of your DSI image. 

Trolling Motor Mount:



Installing the transducer on the trolling motor has one major disadvantage ... it pivots!  Continuous course correction while passing over a POI will give a very distorted image.  The reason for this is that the sound wave is in the shape of a beam, and not of a cone like that of the traditional 200/83/50kHz.  This is especially of concern when using the wide beam of the 455kHz.

The solution to this problem is to approach your POI from a windward position and set a straight course before actually reaching the POI, and keeping the trolling motor pointed directly forward.  Do NOT turn the trolling motor while passing over the POI and split the screen to 455/800kHz for best results.