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Old 05-10-2010, 10:50 AM   #1
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Default HDS cone angle on transom mount set-up

I am running both a Lowrance HDS-5M and 5X (83/200KHZ0. My question is, what is the appx. cone angle in shallow depths. To be specific, I throw a cast net for bait and I am curious of, when I see bait appear on the screen, where it is in proximity to my boat. When the bait ball appears, is it immediately off my transom which means I should loop around? Is it directly under the boat? Any insight/experience is most appreciated.
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Old 05-10-2010, 01:53 PM   #2
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The rated cone angle @ 200kHz for this ducer is 20 degress, but due to large side lobes the effective cone angle can be up to 60 degrees on shallow depths with relatively high gain. For 83kHz I think the corresponding numbers are about 60 and 120 degrees.
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Old 05-11-2010, 05:40 PM   #3
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Roughly 20 for the 200 and 60 for the 83
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Old 05-12-2010, 06:01 AM   #4
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Thanks for the info. In a practical application, is this mainly lateral viewing or is it truly in a cone shape. Based on some old trigonometry, the effective viewing diameter is a little over 11' in 10" of water (60 degrees)....probably a liitle less because fish would hold in some midpoint in the viewable range. What I don't understand is how you go from 60 to 120 degrees (effective).....do you need to modify sonar settings to flip between?
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Old 05-12-2010, 06:24 AM   #5
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you can select the viewed frequency through the menus... you may be able to even display them side by side (or overlayed?) but I've never tried that....
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Old 05-13-2010, 04:25 AM   #6
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if you run sonar plus sonar you can view both at the same time..
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Old 05-13-2010, 05:20 AM   #7
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Typically 60-80% of the energy transmitted is concentrated in the main signal cone, the rest is transmitted in more or less all directions and are called side lobes. Cheap transducers as Lowrance/Humminbird/Garmin 83/200kHz transducers have much larger side lobes than high performance transducers.

A fishfinder can at short distances at high gain detect objects in the sidelobes. This is the reason why the Lowrance 83/200kHz transducer can be rated as 20 degrees cone @ 200kHz, but can detect fish up to 60 degrees. For 83kHz this transducer has a main lobe of 60 degrees, but fish can be detected up to 120 degrees. The figure below is illustrating sidelobes from one specific transducer, this pattern is different for different transducers.

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