What to look for in colour sounders

Once upon a time televisions consisted of black and white screens. They were great. We watched the NZBC news and Happen Inn and we were happy. Then I saw the Jetsons on a neighbour's new colour TV. My life was never the same again.

The first time I went aboard a charter boat and saw the mini colour TV he called a sonar the effect was just as dramatic. The skipper pointed out the tarakihi, the golden snapper and the pink maomao. As good as our then Lowrance paper unit was, this new colour sounder he had was totally awesome. Since that day the only thing that has changed has been the specifications and features of subsequent models, and the quality of the displays. The colour sounder is still the ultimate way to display the greatest detail.

The biggest draw back of the colour units has been, till now, the video tube. They are large, cumbersome, weighty and draw a reasonable amount of power. They still have a place in the market, but I feel the future is with liquid crystal displays.

Remember the old Marlin paper sounders? Small LCD units completely killed that sector. The new colour liquid crystal displays mnay well do the same for the video units, and in the case of key player Furuno, their main range is now all colour LCD. There is one particular reason for this. It's called the TFT screen. It has revolutionised the colour LCD market. Here's why.

Early colour LCD screens had a problem. Move a few degrees off-square and you couldn't see it. You'll still see these screens in cheaper lap top computers. So quickly has technology moved that, in no time at all, these screens have become obsolescent. The current generation have screens that are superb. The rendition of the colours, all sixteen of them, is brilliant.

We often get asked the sunlight question. The LCD is not as badly affected as a video unit, however it doesn't handle it quite as well as the top mono LCD displays (which are superb). It is a non-issue though. Only in directly reflected low level light do we find a problem. The displays have e xcellent brightness and contrast controls. Like all sounders, the quality of the information is only as good as the sum of all the working parts. That includes the transducer.

If you are buying a sounder to work at extreme depths, ask for advice. It is a fact of life that depth costs. And extreme depth costs more. We would expect that the standard transom mount transducer supplied with a Furuno 600L would give a maximum depth of better than 300 metres. But, it can be quickly affected by the quality of the installation, the conditions on the day and the hull it is attached to. Our phone number is printed hereabouts if you want more specific information.

The key thing with a colour sounder is that the signal returned is not shown as either on or off, but rather as a band of sixteen colours, giving sixteen different strengths of return. This gives an amazingly large amount of subtle information not available as readily from other types of sounder. This applies not only to locating fish and recognising t he species displayed, but possibly even more importantly, to understanding the bottom type shown. That is achieved by watching the colour band change below the bottom return. Typically, a band of red is displayed which is similar in effect to greyline in mono sounders. Below this the bottom density will be shown by the intensity of colour and the width of the colour band. It is simple to understand and the first time you see the changes as you go from a soft bottom (mud or soft sediment/sand) to a hard bottom(rock, reef or hard sand) you will immediately recognise the difference by the thickness of the red band (thicker means harder).

Like all sounders, the information displayed is only as good as the pixel count will allow. That's where the zoom screens play their part. The key option from a fishing point of view is called bottom lock. What it does is simple, although a little harder to describe. Basically the bottom is drawn as a straight line. This is unaffected by the terrain or the effect of swell or sea. Above this line a much smaller area is expanded, typically five or ten metres. It is this band that contains much of our desirable target species. By ignoring the bottom and concentrating on the area just above it, the fish are easy to find. We use this screen a lot. The standard zoom screen is really useful when you need more information on the structure itself. Remember though, it is being stretched. It also allows the bottom return to be expanded if required, giving additional information on the bottom composition. This is about as far as we can take describing the screen with words.