Downrigger weights and sonar signatures

[Full_Monte]

Hello Guys. I don't have a lot of experience with my Lowrance fishfinder/gps,
but I notice that my fish-shaped weights produce a large signature (about a quarter inch) on the screen. This is irritating because it often obliterates any fish arches at that depth. When my wife's downrigger "lost" its weight:rolleyes:, I put on my backup weight...a cast iron window-sash weight about 18 inches long. This resulted in a far smaller signature...no more than a line on the graph. In fact, it sometimes disapeared and to see it, I had to change frequencies from 83khz to 200khz. What's going on? Any ideas?
BTW, that sash weight is "worry-free". I have a bunch of them removed from an old house.

[DLM]

No expert here either but here is my guess.

The fish finder is looking straight down. If you are trolling very slow, all it is "seeing" is the top of your window weight, which is about 2 inches in diameter if memory serves me. The faster you troll, the more blow back would occur and the ff should see more of the window weight.

I too was having problems with a large signature from my weight which is a pancake. I did a soft reset on my lowrance and that solved the problem. You can find info on soft resets at their website.

[HiTechKoke]

This is a classic problem with pancake weights and the stick weights (rebar or whatever) will show much less of a profile. Playing with your colorline can help distinguish fish in the cloud. The alternative is to have your transducer point a bit forward so it will see less of the pancake which is what I generally do when running the pancakes. I have not heard of resetting the Lowrance to fix the problem... what that may be doing is resetting or toning down your sensitivity value which can create a bigger signature on the screen if it is set high.

Kevin

[SuperD]

I would think that the sash weight would also have more blow back which might be taking it out of the cone more than the fish weight. But just a hunch.

[HiTechKoke]

True if your stick weights are lighter for sure. I like to make them up as heavy as the pancakes and they run nearly the same, 9 lbs is what I like.

[SuperD]

I was thinking more in terms of the increased surface area and drag.

[Bduck]

My dr weights show up the same way but doesn't bother me in the least. I prefer my showing up so I know where they are in conjunction when I mark fish. When it comes to a school of kokes, there will be plenty of arches. Lone arches are not always in line with the weights. But thats just me.

[SuperD]

Anyone else besides me see the downrigger weight line go through the arch and expect the fish to come floating to the top at any moment? laugh hyst Heck you would have thought they'd bite it or get knocked out by the konk on the head.

[Full_Monte]

It doesn't appear that the sash weight has more blowback than the fish weight..they both appear to be the same. I do have the transducer pointed forward a bit so that I can see the underwater mountains and trees coming a few seconds before the weights strike them. I'm thinking that perhaps it has to do with the sonar reflections and how the geometry of the weight creates those reflections. It would be an interesting experiment to try different weights on the same downrigger with the same fishfinder to see what the differences are.