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Fish finders for techno geeks.
#1
Roads post about fish finders got me doing some math and some home work. Now, if you dont like long technical info posts you can probably stop reading now. But, if you are interested in a neat look at fish finders and are looking into buying one you may find this interesting. I certainly did, and am hopeing some of you can give me some insight into why things are the way they are.

Lets start with the lowrance x-91. It has 3000 watts of power, and sports the capability to go up to sixty degrees on the transducer cone angle. Wow. That means that at a depth of 25 feet you are looking at a circle on the bottom 29 feet in diameter. Thats a big chunk of water! At 50 ft you are looking at 58 feet on the bottom. 75 ft, 86 ft dia, and at 100 ft deep you are looking at a 115 foot diameter. Thats insane! With 240 vertical and 240 horizontal pixels, you may wonder if with 3000 watts of power you can even possibly pick up fish on the outside edge of your cone. If you can, how strong a signal is it, and with 240 pixels, what would it look like? That wide cone angle would be extra nice in shallow water, but I am seriously curious to test it out in the deep. Good thing skeeter just bought one for me to play with.

Now, lets look at the garmin 240. it has 4000 watts of power, and incredibly for the cost comes with a dual frequency transducer! That means you get a 45 degree angle cone, and a 20 degree angle cone. You still have the 240 x 240 pixels. For comparison sake, lets give out the diameters at bottom depths for the garmin. 45 degree trasducer- 25 ft down, 20 feet dia. 50 ft down, 41 ft dia, 75 deep 62 ft dia, and 100 deep, 83 dia. So, you would use your 45 in shallow water, and your 20 in the deep. Your 20 would give you at 25 deep, 9 ft dia, at 50 ft 17 dia, at 75 26 ft dia, and at 100 you would be looking at 35 ft dia. And all with a stronger siganl going down and coming back plus the same resolution on the screen.

Now, this is very interesting to me, I wonder if you start marking fish in 100 ft of water with a 60 degree transducer cone angle and the fish is on the out side edge of your cone, can it even see your lure? Well, that probably depends on water clarity ect. But the general idea remains the same. Are you trying to catch fish that cant see your lure?

Skeeter, open up your box and read the instructions on that bad boy. In the catalogs the x-91 and x-71 claim "up to 60 degrees with asp on" What does that mean? And if the regular cone angle is less than 60 degrees, let me know. I am very interested.

Another thing I did is work up some numbers on the fishin buddy two that is down in my basement. With a nine degree cone, and with its limited battery power source, it still has more effective use than I had thought. At 25 ft down, its at 4 ft in dia. Not very much to look at. But if you factor in its side finding capabilities and combine that with the depth feature you are covering a lot of water. 50 ft down, 8 ft dia, 100 ft 17 ft dia.

Heres the interesting part to me. On my lcx-15-mt I have 8000 watts of power, 480 x 350 pixels, and three cone angles, all of which are smaller than on the x-91 and garmin units. Why? Can someone please enlighten me. On the bow, my angle is 21 degrees. Very similar to the narrow angle on the garmin. on the back, I have a dual frequency that has a 12 degree and a 37 degree cone angle to choose from. But no where near a 45 or a sixty. I would think that with twice the power and twice the pixels, plus superior sound recieving transducers you would find a very wide option for shallow water and a mid range angle for your deep water use. But it doesnt seem to be the case. Granted I dont feel that I need to look at 115 feet of ground when in 100 ft of water. But I find the logic behind this very confusing. Dennis, walleye bob, any of you fish finder gurus, can you help me to understand why this is?

Now to throw a real wobbly into the mix. take your two top end bottom line units, your tournament master HR and your 5300. 18 degree and nine degree angles with five transducers. Only 240 vertical pixels and for some reason 400 horizontal. Why? And only 5200 watts of power. Decent cone angles but without the power and pixels to back it up. Plus no very wide angle option for shallow water. But, you can run your downriggers off it. I am very Confused. Why are the top of the line finders not equiped with all the options, and is that a good thing or a bad thing. Like I say, I am now very Confused. For those of you who are considering buying a fish finder, you may have to work up some info, and determine what type of fishing you do to make the most possible educated decision before you pick one out of the many. I wouldnt know what to do if it was me. I got lucky and just bought mine figuring it was all I could ever want, now I find that I dont know why or why not to want what! confusing huh?

Can someone shed some light on what is good, bad, and why? All the finders are so different but come so close to the same thing. Lets get in depth and crazy with the technical stuff and the opinions.
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#2
The Garmin 240 only has the one cone and the Garmin 240 Blue has the dual cones. These are the two fish finders I got with my boat. As far as telling what is better and why, I haven't really had enough time on the water to figure everything out.
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#3
Now ya gone and done it Pred. I got the Bottom Line 1100. I mean this was really an inexpensive unit (under 60 bucks). No it don't have all the options and the degree of angle is less than desirable. (same as the fishin buddy) But it is going on a float tube, and I can tell you I can't fin it as fast as the fish can swim. My hopes were to be able to teach myself how to jig properly. As I looked at the different models and there are a lot of them! I decided to try the least expensive for the first time out. If it doesn't work as well as I would like, then maybe I'll upgrade. But even at 128 pixels H and 68 pixels V, it has to be able to show me the bottom, structures, and vegetation. I kind of think that it will be up to me to interpret that information and put it to use. At this point in time I don't think I would be able to tell my lure from a fish. I read the one guys post that said he could see his swivel, I have trouble seeing my line to tie knots anymore! So i opted for the basic of the basic units. If I find I need more I will pass this along to FB2 and then we both will have something. But I honestly could not ever put one of those top of the line sonars on a float tube. It's the penney pincher in me guys. I could spend a fortune on a rod or reel, even a boat (I have my dream boat picked out) but for a tube sonar nawww. But what i have learned is I knew nothing and need to do more home work. Thanks pred ya opened my eyes. Now when I get my boat I'm sure I'll be spending more the 60 bucks on a good sonar and GPS,

That was pretty interesting to see that a 9 degree tranducer has such a limited field of view. That alone may make me change my mind. Geez now I'm lost and Confused also.
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#4
You may find this sonar range calculator of interest if you have time to burn and a desire to see how various environmental and system parameters effect sonar range. You'll probably need to do some research on the sonar equations developed back in WWII before you can use it very effectively. There isn't much help or instructions.

Sonar Range Calculator

[url "http://freespace.virgin.net/mark.davidson3/JavaScript/SEcalculator5.html"]http://freespace.virgin.net/mark.davidson3/JavaScript/SEcalculator5.html[/url]
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#5
First of all thanks Predator for giving me a reason to open my christmas prestent a little early this year. I got an Lowrance x91 this year for christmas. I looked all through the instruction manual and I can not find any info on the 60 degree cone capability. The transducer that comes with the unit is 20 degree. the only thing it says about the 60 degree angle is it will read up to that with the higher sensitivity settings.
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#6
Yeah, I went over to lowrances web page to look for the answer my self. The accessory transducer was a 20 degree, but I couldnt find anything about the sixty degrees either. Thanks for looking.
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#7
[size 2]Predator, your answer is in the PDF at this link...[/size]

[url "http://www.airmar.com/Technical/tech_index.html"][#800080][size 2]http://www.airmar.com/Technical/tech_index.html[/size][/#800080][/url]
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#8
Just to let you Know Lowrance just came out with a new fish finder the x97 it looks nice. It has all the features of the x91 but it has more pixels.
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#9
Hey Predator, I have a theory, but thats all it is. I think when you have too wide of a cone angle in too shallow of water,the return signal gets lost out in never never land instead of coming back to the transducer with enough power to do much good.
For the kind of fishing I do, I like a small cone angle. I'm usually fishing structure, dropoffs, and with a wide cone angle you lose too much info. When going downhill or along a steep bank, the finder only shows whats on the uphill edge of the cone. The closest return signal. Everything else is a blind spot. When going uphill you can see fish hugging the side of a wall because they are on the leading edge of the signal.
If I fished more for open water fish, like Wipers at Willard, a wide angle would be my choice.
Even with really wide cone angles, you reach a point where the signal stops going out. The cone angle is shaped more like a balloon. So in deep water, you might get out to a 80' or so diameter and then it stays that diameter even when you go deeper.
All things together, I think your unit has a good set of transducers. Very useable, without too much screen clutter.

Good fishing everyone and have a safe X-mas.
WalleyeBob
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#10
One you guys have left out is RAYTHEON fishfinders.

I own a L365,which is working great.

300watts RMS/2400watts peak to peak.

Really like the A-scope option which is real time when vertical jigging,works great in deep water jigging.and ancored up when I fish for perch.it also tells you the dia.of the circle on the bottom.

has dual frequency 50khz/63degree cone angle,200khz/16degree cone angle.

pluse side finder transducer(OPTIONAL)

not the big screen,240X64,but has all the great options the more expensive units have.I spent $200.00 new for it.3yrs ago.

Works Great,and got it for a great price.look into this one Predator would like to hear some input.on what you guys think.

web page:WWW.RAYMARINE.COM

Tight Lines.

Tony
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