reading a fishfinder

[ThomWV]

Re: reading a fishfinder

Bill,<br /><br />Before I went in the Army in 1966 I had never seen a fish finder. I started fishing with fish finders a couple of years after I got out, in 1970, with those old Lowrance flasher/paper chart machines (MGR 600 or something like that). We used to do a lot of dead bait fishing over on the Gulf side and down in the keys back then. Then we moved up here and I got to fishing from the Outer Banks in the mid 80's and several manufacturers started putting out smaller video machines that you could actually afford. We had moved to deeper water by then and a depth finder became of less and less importance to me. For years I really didn't even care if one was on the boat other than for speed and temperature. Anyway I used those video machines up until the mid 90's when I briefly had an old Furuno LS6000. We got rid of it and got a 600L, which was very nice, and then we sold it and got a 582L. All during this time I was doing a lot of fishing with friends a little installing on the side so I was able to see quite a few machines in action. Just lucky I guess. Anyway I've been playing with them for a pretty good bit.<br /><br />As for the zoom, I never use it. I never use A-Scope either for that matter and very rarely split the screen either. For the most part I just set a fish alarm for anything that passes between 25 and 150 feet below the boat and then stick it in automatic. We'll watch it a bit sometimes, more to watch bottom contur than anything else, and of course its a display point for the water temperature (which we watch like a hawk). I know there are guys who are finatics about their depth finders and picking up every hint of anything that is down there and going to all manner of artful tricks to dial in the manual tuning just exactly right, but we're not much like that. If we were bottom fishermen I'm sure it would be different but trolling is all we do so seeing bait and just generally keeping an eye on what's going on is about all we do with one. With all that said, though, if we're going to have one onboard I want one that works and one that works as good as I can possibly afford. To the extent we can afford it I simply do not like to use second rate equipment.<br /><br />Thom

 

[Boatist]

Re: reading a fishfinder

Handball<br />I got my first depthfinder in 1981, before that I had seen a lot of paper graphs and had decided they were not worth having. Spent more time working on the unit and putting in dry paper than fishing. <br /><br />Since I got my LCD unit I read my owners mannual have ask questions at boat shows and recently searched the internet. One thing that was a big help to me was to go out on a clear lake where I could see the bottom and then relate what I saw on the screen to what was actually on the bottom. I have spent many days out on the water, and fished all my life. In my area lots of Black Bass fishing clubs. I have fished with many friends in these clubs and fished some tournaments. Many of these clubs invite experts to come to the club and show how to use the depth finder to find and catch fish. They will explain many tips and tricks. Since these experts are paid many of the clubs will invite friends and sometimes even the general public for a very small fee so they can gererate the money to pay the experts. These guys are also usually selling a tape or book with very good information. Since learning a lot about them I would never ask a rep at a boat show anything as 90 percent give very misleading information. You can still learn at the boat shows by asking the party boat captains what they look for an what trick they use. Most will be glad to share when in there booth and not too crowed. Also if take a trip on a party boat captain and crew can really help.<br /><br />Zoom is very important when fishing bottom in deep water. As A example fishing for bottom fish in 400 feet of water with a depth finder with a resoultion of 240 vertical. 400 feet times 12 inches = 4800 inches. With 240 vertical pixels each pixel = 20 inches. To see a fish on your screen you really need to have at least 2 pixel filled. Two pixels would = a fish 40 inches high. Not many fish 40 inches high. With 4 times zoom the fish will fill two pixels if he is 10 inches high. That still a big fish. If your unit has a 8 time zoom then fish only need to be 5 inches high. Really to fish that deep better to get a depth finder with a higher resoultion of at least 480 vertical. also need to remember with a 4 times zoom fishing 400 feet deep your screen will only display from 300 feet at the top to 400 feet at the bottom. A school of Salmon or Tuna at 30 feet deep you will not see. Some depthfinders have another way to expand the bottom. My unit has a feature bottom track. I can set it to display the bottom and up 10 feet. Set this way each pixel would equal 1/2 inch. I usually set mine for bottom and up 40 or 50 feet. Other units like your furuno have a feature called bottom lock which will let you lock on the bottom and up so many feet. I really do not like this feature as the bottom will look flat even when big rocks or drops off but you will be able to see fish.<br /><br />Any way just takes time and a little effort and you can learn as much as you need.

 

[handball]

Re: reading a fishfinder

Hi fellows,<br />Yesterday while sitting in a slip I tied a 8 lb. galvanized cast iron grapnel anchor to a lenght of nylon rope and lowered it along side my 30 ft. sea ray.I tried to get it as close to the transducer as possible.The water here is about 20 feet deep and I tried to see the little anchor on the f.f. by raising it off the bottom and lowering it about 3 feet, could not see anything just off the bottom. Also tried holding it at different levels, still did not see anything.I then switched between 50 and 200 khz still could not see the anchor.Is it possible at this depth the cone is too small to reach out to say 6 or 8 ft. from the transducer? I also tried to increase the gain and decrease the gain from its normal setting. Is there anything else to adjust or try?<br /><br />The fishfinder seems to work fine otherwise.<br /><br />Bill

 

[ThomWV]

Re: reading a fishfinder

Bill,<br /><br />I was able to watch a 1 oz sinker go to the bottom in 100 feet of water with my Furuno 600L. I now have a 582L and am using one of the super high performace transducers with very narrow cone angles so I'm sue I could do better now. You had to be outside of the cone, which seems improbable considering how wide the cones are in standard transducers, which is what I assume you are using.<br /><br />Thom

 

[Boatist]

Re: reading a fishfinder

HandBall<br />I belive your transducer is 11 degrees at 200khz and 45 degrees at 50 khz. With the 200 khz 11 degree you would see a 4 foot circle on the bottom in 20 feet.<br />The 50 Khz 45 degree should see at least 14 feetcircle. Does the depth finder show the water as 20 feet deep. You should be able to see a anchore unless you have something very shallow giving a return. If something very shallow is giving a return then the bottom should not show the depth at 20 feet.

 

[18rabbit]

Re: reading a fishfinder

Originally posted by ThomWV:<br /> ... am using one of the super high performace transducers ...

I think that M256 is actually a super-duper high performance transducer? <br /><br />Never mind. I'm crawling back to Dockside Chat.

 

[handball]

Re: reading a fishfinder

Hi fellows,<br />The transducer is a bronze airmar unit that has a temp. sensor and speed wheel.<br />The f.f. clearly shows the bottom at 20 feet and I have another depth finder on board that agrees with the furuno.The transducer is mounted to look straight down and is about 1 foot away from the keel.The boat has a beam of 11 feet which puts the weight I dropped about say 5 to 6 feet to the side of the transducer.<br /><br />I guess the little anchor is probably outside the cone angles.<br /><br />Next time I go out I will try the same thing in deeper water, say 40 feet and see what it looks like.<br /><br />This little experiment gives me a better feel for what I am seeing in the bottom contours as the boat moves under power.If I am in shallow water the pockets in the bottom must be small and within the beam of the boat in size or I would not see them.<br /><br />Bill

 

[18rabbit]

Re: reading a fishfinder

Originally posted by handball:<br />The f.f. clearly shows the bottom at 20 feet and I have another depth finder on board that agrees with the furuno.

Bill - This is not necessarily a good thing. If there are two transducers working on the same frequency, at the same time , they definitely can interfere with each other. Dual transducers need to be working on different frequencies. If your ff is 200kHz and your depth finder is also 200kHz, there may be a conflict when both are operating at the same time. Also, the recommendation for mounting two transducers suggests no less than 18-in apart. That isn’t necessarily necessary. Hint: the higher the frequencies, the closer they can be mounted. A 200kHz and a 233kHz can be mounted a couple inches apart without interfering with each other.

 

[BoneDigger]

Re: reading a fishfinder

If you were anchored at a spot and the boat was not moving and there was a catfish sitting on the bottom, would you be able to see the fish? It seems, based on what I've read here that the fish would show up as a single line going across the screen, parrallel to and on the bottom. Wouldn't the catfish show up as a part of the bottom in that case?<br /><br />Todd

 

[Boatist]

Re: reading a fishfinder

If the catfish is right on the bottom he will likely just look like the bottom. With the 200khz if he is not tight on the bottom then you might see a line acrossed the screen just above the bottom. Adjust your grayline/whiteline/colorline for a thin bottom line for a better chance to see him.<br /><br />If the catfish is on the bottom next to a log or on a sloped bank in a little deeper spot then you will never see him.

 

[craqpot]

Re: reading a fishfinder

I'm learning a lot here about my touchy Furuno 4100, which I use in a 20' wooden outboard skiff, on inshore waters. The transducer is transom mounted, by the book. <br /><br />Understood that there's superior resolution in 20' of water at the higher frequency. But that 14' diameter cone seems tremendously more useful than a 4' cone (which can't reveal an anchor 20 feet down 4 1/2 feet from the transducer!).<br /><br />The resolution at 50 khz can't be so poor that 200 is necessary. More learning is necessary I guess, because I can't understand how the tradeoff makes a lot of sense for most situations. What's the objective for signals at 200 khz/20 feet? <br /><br />handball--- I've spent a lot of time fiddling with permutations of manual settings under various water, motion, and bottom conditions, with clarity of the images no better than the auto settings. Can't switch on a fish alarm... that creates a din of false alarms, without regard to frequency, sensitivity or gain settings manually, or auto. At least on my new sounder in water depth less than 60 feet. <br /><br />Hate to say it, but a friend brought out a cheap old humminbird with a suction cup transducer. Depth contours were in absolute agreement, while the clarity of his screen and his fish signals were superior. I'm OK technically and he's actually an electronics professional and repair wizard. We tend to express, shall we say, "disappointment" with my Furuno 4100.<br /><br />You've been infinitely polite, but I wonder if your 6100 is mightily similar to my gray screen 4100.