Question About DI Images

[John Doe]

I understand that DI sends a thin beam down and out and the returns paint an image on the screen.

My question is can the image portrayed on the screen give you a clue as to whether the structure/fish seen is under, to the left, or to the right of the transducer?

[ShilohRed]

Your DI has three settings same as the 2D. Narrow,med and wide. When mine is on Narrow and I'm fishing brush. I can see my jig (1/8 oz) on it at times. So I would say any fish in the narrow beam is under you. I do have the refresh rate high to do this. If you have it set low it paints a good pic, but can't see the jig or fish coming for it.
Pete

[CrappiePappy]

Only "settings" I'm aware of on a DI is 455mHz or 800mHz. 800mHz gives you a 45deg beam & 455mHz gives you a 75deg beam. The total swath of a 800mHz beam is 0.83 x bottom depth ... 400mHz is 1.53 x bottom depth.

I use 800mHz & fish in 20fow ... knowing that my beam swath is ~16ft wide. (or ~10ft wide at 12ft depths). I also get a clearer image.

Do I know which "side" of the boat the image is coming from ?? No, not really. But, I do know that it has to be within the limits of the beam swath, in accordance with the depth of water I'm in.

[John Doe]

Thanks for the reply CP and Pete.

I have my transducer mounted on the TM. Sometimes I get great images with "shadows" off structure. It's hard for me to explain and I should capture some screenshots. I wonder whether the shadows are due to the structure is between the beam and a slope like a creek channel.

[genec]

john doe,send us some pic,also what unit do you have?

[John Doe]

I am using a HB 859CI HD. I keep forgetting to put a memory card in the unit. Inevitably, I remember that I forgot when I get out on the water. Gonna install one tonight. I doubt I get out on the water till this weekend.

[rnvinc]

Shilored's info about Narrow Medium and Wide would be if you had a core series HB SI unit ...

With your unit being the 859ci HD DI = pappy's info of the 455kHz fan beam being 75° and the 800kHz fan beam being 45° is correct ...

Left and right in the fan beam cannot be discerned ...

Rickie