Fish arches ONLY in the 50khz mode?

[Basenjib123]

I have a Furuno LS6100 Dual Freq. 50/200khz FF (great unit), anyhow, I notice that I only get fish arches in the 50khz mode as opposed to the 200 khz modes. This occurs in mostly water 20-40 feet deep. The arch thing isnt that big of a deal to me but I am still curious about it just the same. Any ideas on this, thanks..Joe.

 

[Boatist]

Re: Fish arches ONLY in the 50khz mode?

Joe<br />I would start by turning up the sensitivity until you start to pick up false targets on the 200. The 200 khz mode transducer is probably a 20 degree cone angle and the 50 is a 45 degree cone angel. So the 200 should still see fish if directly under the boat but if out to the side only the 50 will due to the wider cone angel. The 50khz will always draw a better arch as the fish is in the cone angel longer. Also as you pick up speed the 50 will see fish longer and get more returns while the fish is in the cone. The 200 if have any speed may only get a couple of returns while the fish is in the cone angel and not draw much of a arch at all. The 200 is more critical that the transducer is pointing straight down or you will only get front half of arch or back half of arch.

 

[Mumblerone]

Re: Fish arches ONLY in the 50khz mode?

Boatist...I have to disagree with your last sentence. If a fish tail is in the cone (not really a cone, but close) you'll get a mark. This mark could be a very large fish, but you don't know. Very hard to tell fish size , without a full arch; and then it's only relative. Of course, you also don't know what part of the cone (360 drgrees) the fish appeared in; only the distance. Nothings perfect.

 

[Boatist]

Re: Fish arches ONLY in the 50khz mode?

Mumblerone<br />I will try and explain my last sentence better. With a 20 degree transducer (standard for 200khz) if you mount it where it points 10 degrees forward and you move over a fish not moving on the bottom then you will only get the first half of the arch because when the fish is closest to you or straight down it leave the cone. As you approch the fish and it is 20 degrees in front of you, you will get returns back and be displayed as the lowest part of the arch as you countinue fish gets closer unitl it is straight down and displays the highest part of the arch at this point the fish leaves the cone and you never see the back part of the arch. With a 45 degree (standard for 50khz) if you have it pointed 10 degrees forward you will still get the front part of the arch and 12.5 degrees of the back of the arch. So as I said to display good fish arches it is more critical for the 200khz to be pointing straight down than the 50khz.<br /><br />As far as size a number of things will give you a good idea. The thickness of fish from top to bottom, also if your fish goes into gray line. Large fish you can usually see the bladder. Your right if the fish is out in the outer edge of your cone it will not look like a fish.<br /><br />Joe question was why he does not see arches in the 200khz mode and I gave him some things to look for. If you have different ideas please share.

 

[Mumblerone]

Re: Fish arches ONLY in the 50khz mode?

Just wanted to make sure we're on the same page. Have a great day!

 

[Boatist]

Re: Fish arches ONLY in the 50khz mode?

Joe<br />I checked Furuno web site for the LS6100 and the transom mount dual frequency tranducer. The 50khz has a 40 degree cone and the 200khz only has a 10 degree cone angle. So you will only see 1/4 as much bottom with the 200khz, so only 1/4 as many fish. I have a 8 degree cone angle on my 192khz transducer and I can tell you I see a lot of fish but they do not make much of a arch. They have some curve but a lot straighter than you see in all the adds. I also have a 20 degree 192 khz transducer that makes nice arches is shallow water. I use the 8 degree when fishing in over 150 feet of Salt Water.

 

[Basenjib123]

Re: Fish arches ONLY in the 50khz mode?

Thanks for the replies!