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Location: Green Bay, WI | Anyone know the angle that the Lowrance side-scan beam is directed? I am wondering how close to 180-degrees of coverage does the unit provide? This is important because you then would get decreasing coverage of the water column as the beam got farther from the boat--and you might then miss shallower targets out there.
TB |
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Posts: 2323
Location: Stevens Point, WI | This all depends on the depth of water and how far you have your unit ranged out. Sometimes it's 40ft, sometimes it's over a 100+ ft in deeper water. The shallower the water the less effective it is because you can't range out as far.
Sidescan Specifications:
Max Range: 455kHz (500ft — 250 per side) 800kHz (300ft —150 per side)
Max Speed: 35 mph (56 kmh)
Mark objects: 15 mph (24 kmh)
Optimum speed: 10 mph (16 kmh) or less
http://www.lowrance.com/en/Products/Marine/StructureScan-HD/Feature...
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Location: Green Bay, WI | Well, but the *angle* of the transducer beam should not depend upon the depth at all. The angle of the beam, is the angle of the beam. It's the angle the beam comes out of the transducer. The amount (volume) of water covered IS dependent upon the angle however.
For instance, if the starboard side of the transducer has a crystal with a 90-degree beam width (say 45-degrees either side of zero), and the crystal is pointed down and right at 45 degrees, then the arc scanned by that beam is from straight down under the boat (-45 degrees), to just under the surface of the water on the starboard side of the boat (+45 degrees). So in that case, an arc of 90 degrees on either side of the boat, would give you 180 degrees of water coverage--and the limits of your scan would be the bottom of the lake, or (as the beam moves out farther to the sides) the point where any sonar returns from targets are so weak that they are not strong enough to be perceived with certainty. But that's with 180 degrees of coverage...90 to the left, and 90 to the right. But I doubt that is what's going on here.
My guess is that the beam width for each half is something like 70 degrees, centered around the +/- 45 degree points on either side of the boat. So then there is an area directly under the boat being missed by the side imaging beam, and also a triangle-shaped column of water that is getting larger as the beam travels out from the transducer. So if it IS a 70-degree beam width (symmetric on either side), that means that about 10 degrees of coverage is missed under the boat, and 10 degrees are missed out to the side of the boat. Therefore:
tan(10) = height of missed water column / distance from boat
0.176 = height of missed water column / distance from boat
So at 100 feet out from the boat there is about 17.6 feet of water depth not being scanned, starting at the surface.
The importance of this is very simple--if you are scanning the basin of a deep lake (e.g.; Trout Lake in Vilas County) looking for bait fish, you need to realize that because of the beam width, you aren't going to be scanning the upper 18 feet of water 100 feet to either side of the boat. And as active basin muskies are often shallower than you might think, this becomes very important. Simply put, you might be scanning UNDER the bait fish (and any muskies!) that are sitting out there 100 feet to either side of the boat.
You're looking for a needle in a haystack out there to start with--you may as well do it knowing whether or not both eyes are open.
TB |
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Posts: 676
Location: Wisconsin | The beam is very narrow, but it is taking a slice of the water from perpedicular of the transducer. The beam won't spread out much at distance but starts to attenuate or reduce signal strength. I'll see if I can dig up a diagram....
(Lowrance Side and Down Scan cone angle.jpg)
Attachments
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 Lowrance Side and Down Scan cone angle.jpg (136KB - 1726 downloads)
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Location: Green Bay, WI | Ah...I've seen the larger diagram, lower in the picture. What I haven't seen though was the top diagram. According to that, the beam is basically directed out parallel to the water surface. So then it really doesn't matter what the beam angle is, as they simply bias (rotate) it upwards to give the upper edge of the beam a path parallel to the water's surface. So then you ARE interrogating the upper portion of the water column all the way out to the limit of the usable signal. Awesome...
That's the information I was looking for. Thanks MM!
TB
Edited by tcbetka 4/18/2012 3:51 PM
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Posts: 676
Location: Wisconsin | Remember if you are installing this transducer that the beam can be disrupted near the surface by anything sticking out from the boat like filter screens, other transducers. Some guys have been putting in a spacer to move the ducer out a bit. Someone on here had posted some pics of an install. I have even seen one install on the jack plate. |
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Location: Green Bay, WI | Well, but the transducer is basically the lowest thing on the back of the hull for the most part. So while this might be an issue, I don't think it will be too much of a problem given the depth it's mounted under the surface. I understand what you mean about the space though, and I'll keep that in mind if there's some interference when I start using the units.
I guess I would worry about moving it *too* far out though, as it seems like you'd be into the lower unit of the motor in that case.
TB |
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Posts: 559
| Tom I find the last few post of yours interesting. I think you are doing about the same thing I am. I am adding LSS1 and HDS 7 for a total of 2 hds7s 1 hds 5 and LSS1 I think I am going to try it on one batt and see what happens. I am now confused about where to mount the ducer for the structure scan on 1760 tuffy. Any help is welcome.
Thanks
Louie |
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Location: Green Bay, WI | I have not yet fully decided on the number of batteries on-board, to be honest. Common sense tells me that a separate battery to isolate and power the electronics, is the most prudent way to go--but it also adds weight, cost and complexity to the system. So I am still thinking on that.
As for the LSS-1 installation, try this link for some pointers...
http://www.youtube.com/watch?v=XmR500kNNz8
You may have seen it already, but it's worth a few minutes to watch it. I found it useful to review the basics anyway.
TB |
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Posts: 559
| That helped a little but will it hit the lower unit with the right side image |
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Location: Green Bay, WI | I'm not so sure it will. There was a fair amount of talk on TheHullTruth forums about that, and people said that there wasn't much of an issue. I don't know if they were using those Starboard mounting boards though. But have you seen the LSS-HD transducer? It's quite a bit longer than this one!
I'll be anxious to get my boat and start measuring and planning the installation. But I think that the motor will be trimmed up far enough for it to miss. Keep in mind that you're really only using the StructureScan unit at idle, for the most part. So you can simply trim the motor up and out of the way when you want to use SS...
TB |
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Posts: 676
Location: Wisconsin | There is a top speed limit for the LSS, so it being in the water at speed isn't critical if that helps on install. It just has to be able to clear shot to the sides, and cavitation in and around the motor area will effect it some.
For batteries, I run Cabelas AGM's and they have the best amp hours of pretty much any battery. I have a series 27 in the back and I have two HDS's and a ton of accessories and have never worried about them. Best batteries for the money. |
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Location: Green Bay, WI | That's why I say it will work better at slow speeds, when you can just trim the engine up and out of the way. I think Doc Samson's videos say it seems to work best around 3.5-4mph, but he has gotten it to work at higher speeds than that. But the optimum speed is slower though, as you stated.
TB |
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Posts: 1
| Setting up the structure scan transducer on my boat. Not sure of the best location and looking for a bit of advice. Will attach a few images.
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Transducer Locations.docx (198KB - 495 downloads)
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Posts: 1209
| With my humminbird i say the angle is approximately 175* with my gen two hds touch and lss2 I say approximately 150-155*. You will miss suspending fish near the surface and bait. |
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Location: Eastern Ontario | Looking at the coverage diagram I'm not understanding why I'm marking the tips of my down rods at leasr 4 feet ahead of the transducer. |
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Posts: 1209
| The line not the rods what you are marking or air bubbles |
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