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