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New Side Scan for my Old boat #13601821 06/20/20 12:06 PM
Joined: Apr 2008
Posts: 869
Big Hopper Offline OP
Pro Angler
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Pro Angler
Joined: Apr 2008
Posts: 869
I don't visit this section of the forum very much, if ever, so these questions may have been asked a million times.

I just bought a new Garmin 9sv, and I am getting ready to install it myself on my 1986 Charger Bass boat.. So, I decide to actually read the instructions for a change.

1.) I want to mount the transducer on the transom and the instructions say to "Not run the transducer cable close to electrical power wiring". The only obvious place to run the cable is under the gunwale along with all of the other outboard controls, steering cables, and Power Cables from the battery to the dash etc. Where else can it go? Is 12v enough power to cause disruption?

2.) The only mounting instructions included are for trolling motor mount, or transom mount, with the transducer hanging off of a bracket screwed to the outside of the boat. Is this the way Side Scans have to be mounted? The last two sonar units that I had were epoxied to the deck inside the boat near the drain hole. There are also warnings about setting it a minimum distance from the propeller.

I'm glad there are wine drinkers in this world ..... it saves more beer for the rest of us.
Re: New Side Scan for my Old boat [Re: Big Hopper] #13601938 06/20/20 02:26 PM
Joined: Feb 2015
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Flippin-Out Offline
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On #1, realize that the signal from the transducer is extremely sensitive, probably beyond what you realized would actually work. Think 1/10th of a volt ballpark as an absolute maximum amplitude level. Thousandths of a volt matter when trying to "build" a visual representation of the lake bottom. That makes "just 12 volts" be 120 times or more higher than the sensitive transducer analog ping and return signals. Now, when a cable with data signals (represented by the frequency and voltage of the signals on the transducer cable) are parallel to and close to other wiring, a phenomenon known as "signal cross-talk" occurs. The bigger the amplitude different, the more intense the cross-talk. The closer the wires are together, the greater the cross-talk. The longer they are in close proximity (measured in feet of the proximity run), the greater the cross talk. When cross-talk happens, signals are affected by the nearby wiring, and they no longer look they they did at the beginning of the journey from the transducer to the display unit. So, the chance that signal interference affects one installation or another is up for chance, given so many factors. Depending on how the cards stack up in one installation vs. another, one might get away with it, while another does not. As with all installation manuals, they're making that warning in simple terms.

Yes, there is somewhere else you can run the cable. Who said the transducer cable had to be bundled with all the other wiring? Nobody. You can run the wire thru holes in the hull where it is close to other wiring, but minimize how many feet of the cable run this is happening. I'm betting that transducer cable is way longer than you need. Once you get it run inside the hull (inside the side-wall of your boat), you can let it drop down to the bottom of that hollow space. Don't go to efforts to tie it up to the other wiring bundle - that's going the other way from what you want. Just letting it drop down away from the other wiring bundle gets you a foot or more in separation. The transducer cable is shielded, so that foot becomes about as good as a mile. Problem solved. BTW, all those extra feet of transducer cable....do NOT bundle it up and zip-tie the slack. A signal going down a long cable can actually cross-talk with itself. Think of it like magnets moving through a maze. As two progress at different points in the maze, they are close together through the maze barrier at times, and will attract each other as they pass. Signals on the cable do the same. You want that extra length randomly spread out inside the wall of the boat for the best signal quality.

On #2: To give the high definition and side view sonar images, there are man crystals that make up "the transducer". "Transducer" like you mention used to be epoxied inside your hull did have just one crystal in it. It was a simple single frequency operating device, and that crystal was on the bottom of the housing facing straight down. Today's "transducer modules" can have a dozen or more crystals in them, operating at 3 or more frequencies, located to face three directions from the module - left and right at different angles, and down. This is why you can no longer just put it in the bilge with some epoxy. Those days are over unless Garmin supports a second transducer for the "old style" signals for getting depth info when you are running on plane. Otherwise, you have to figure out how to handle this outside on the back of the boat. What you do depends on your goals. If you're not trying to make that unit give you depth info when running on plane, the install is less complicated. But, yes, that big transducer module has to be outside in the water. For my brand (Lowrance) I mount the module on a special bracket attached to the side of my jackplate at the bottom so I can avoid the difficult task of trying to find the perfect spot on the hull, and possibly being required to move it if it does not work well in a spot I pick. I looked up your instructions. That warning about being close to the propeller is 15 inches! The prop on your Charger is probably 24-30 inches from the transom. Think about that.

If you have a jackplate, the brackets are worth every penny. Your transducer should be mounted on the right side of the boat's centerline because the prop pushed water to the left that can disturb a signal there. Keep in mind a transducer "looks" in a line of sight. It must be able to "see" to the left and right from its position without obstruction in order to give you that side-scan image. So, it must be mounted such that nothing in blocking its' view to do this. Be cognizant on where & how you mount the module. I can't tell you the number of times I've seen instantly what problem someone has when they say they can only see to the right side of the boat in sidescan. You need to get some good conversation going with the Garmin bunch here or on BBC to find out how they mounted theirs (that works as intended).

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