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To have the best of both worlds, that is; shallow and deep water reading capabilities, you can aquire a dual cone angle transducer. Perhaps some Sonars are fitted with these. Most are not, as that is a fancy feature on high end models. This dual cone angle feature is not to be confused with the dual frequency capabilities of say the Ray L750(50 and 200 KHZ). I am talking now about the the cone angle(beam) of the signal that you send down into the water. Basically, in shallow water you want a wide cone, and the return signal can then be very detailed without clutter(noise). The wide-angle for the shallow water readings is between 12 and 19 degrees. This same wide signal cone shooting down to 400 feet would loose resoloution and require higher gain setting, which will muddy-up the screen and result in more noise and usless data. The deeper you try to read, the wider the cone is spreading-out. Think of the sonar beam as similar to a flashlight's beam; the further you shoot it, the more diffused it becomes. Same thing goes for sonar (acoustic waves). Also, too much information and bottom coverage is not good. You want to read a fairly small spot right under your boat usually. So to prevent that scattered, difuse signal return, the deep water cone angles are kept narrower and between 6-9 degrees. They shoot deeper with more clarity. These narrow beams allow you to read the same bottom area (footprint) clearly at depths as do the larger beams in shallow water. To visualize this, draw a cross section of the water's surface, then your Yak at the surface, then the bottom at 30 feet and a drop off to 400 feet. Keep it porprtional to get the true effect. Use quad ruke paper. Then take a protractor and make a couple of different cone angles and project them to the bottom in both the shallow and deep water. You can now readily see the difference in bottom coverage when using narrow vrs. wide angle sonar transducers.

You raelly want both beam sizes (cone angles)if you routinely fish both depth ranges. I'd call anything over 100 foot deep deep water for the sake of the argument. Personally, in waters over 80 feet deep, I'll switch to the narrow cone angle crystal, since I have the option. It makes a big difference. Now the dual capability can amount to having two seperate transducers that you physically switch, or it can be a single transducer that has both crystal elements inside of it. Having a "dual element" tranny allows you to employ a toggle switch that selects the appropriate cone angle for the water you are currently fishing. (I have this set up and it is sweet) Note: saltwater is harder to shoot through than fresh, so usually a narrow cone is best for optimum readings, especially at depths, in salt water.


What to do? Look at the specs of the sonar you are using and/or are thinking of buying. These days, the Fish Finder manuals are often on-line at the manufacture's website. Then if you can get the optional tranny and switching capabilities from the factory for your unit, great-do that.


However, if that is not an option for your unit, and or budget, you still have a great option. That soloution is to contact Max Chavez. His website is: Http://

He can supply a selectable, dual cone angle tranny custom built for "YOUR" particular sonar unit. While you are at it, why not have him build it into a wet cell style tranny for overall superior performance. Also another option through Max is buying the "scupper hole tranny"- a very elegant soloution for a lot of us paddlers(I have these as well). If you fish a yak that has mondo-sized scuppers, then the "dual cone element" style tranny (a bit larger than standard single element sized pucks) may even fit in your yak. If so, you are in luck!. You really need to check, via e mail, with Max if you have the bent for hi-performance sonar fish/Structure finding.


I use Vexilar sonars on my kayaks, and they offer many optional trannies of differing shapes, sizes and cone angles right from the factory.




If I had to choose one tranny, it would be a narrow cone.


Hope this helps rather than confuses the issue. Here fishy fishy fishy....





[This message has been edited by sharp1 (edited 01-11-2002).]

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Could you try and be more specific in yuor responses??!!wink.gif

You appear to be very well informed and more than ready to share that knowledge.

Fine qualities indeed!

DASBOOT biggrin.gif

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Doesn't the frequency determine the cone?


Ugh, good question Oznavad. I had previously used a ray-L750 and that unit, a rather big and costly one at that, had dual frequency capability. It also had Huge Pucks.


To directly address you question, the L750 device has published specs as seen below:

Raytheon L750 =

50KHz/65 degree beam (cone angle)-

200KHz/16 degree beam (cone angle).

As you can see above, and deduce from the previous info I posted, for shallow waters; the 50KHZ tranny would be best. This particular 200khz tranny is quite a bit narrower in comparison to the 50 KHZ tranny. The L750 is an $1,100 dollar machine and pucks are extra! It allows a split screen view of both trannies simultaniosly, which is exciting. Almost too much data for a kayak angler to crunch; at least for my brain coral mass. I can grok the toggle moves between the cone angles though.


Most low-priced fish finders use 200 KHZ technology. My Vexilar is a 200 KHZ machine and so are most Hummingbirds, Lawrence's, Garmins and other similarily priced devices. So you can still select narrow and wide beams within the choices available for the 200KHZ machines. Use the "Right tools for the job" has been said. I try to do that. Sometimes I even catch a fish!



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