I have a pretty basic question here in terms of which Khz are most of you guys using? My HB 787 allows you to switch between 83khz and 200khz.

I've looked into this as I've noticed I never get the tell tale boomerang fish patterns when operating at 200khz

With my experience the 200khz seems to operate much better than the 83 Khz when it comes to any boat movement, other than a drift. In addition, it seems to sort through the noise of heavy weeds.

In contrast the 83khz marks more fish but when around heavy weeds or at speed, it's a cluttered and indiscernible.

I've got the sensitivity of both khz set at about 75% per most of the "experts"

Thoughts? Feed back? Or should I just use the split screen? Thanks.

Use whichever one suits your needs best, that's why they give you a choice. 83khz has a much wider cone, so you get much more pronounced fish arches with it. That wider cone also covers a lot more area, which shows more fish. The result is that small fish look bigger, and fine structure such as weeds get crammed together into the same resolution, so they tend to blotch up together.

Basically the opposite on the 200 khz frequency, narrow cone angle, so you get more definition of fine detail, but smaller, less pronounced fish arches.

I usually use the combined 83/200 khz view (both frequencies superimposed over each other). With experience, you can easily tell which parts of the image are from each frequency. Sometimes I use only one or the other.

There's no right or wrong answer, use the one you like best, or both for any given situation.

The lower frequency element of the dual frequency transducer is able to penetrate deeper water better. As I usually fish in less than 40', I would always use the 200kHz 'ducer, as it will provide better resolution. you may simply need to adjust the setup a little. See link below:

http://www.fishfinder-store.com/dual-frequency-transducer.html

Really the best way to run all of these Humminbird units is in Dual Mode or 83 / 200 mhz.. Makes a night and day screen display once you understand what you are seeing.. Remember the 83Mhz is a wide angle cone down and the 200 Mhz is a narrow angle cone. Put these two together and you will get the whole picture.

Try this, find a tree or a brush pile that you know is there.. Run over it with the 200Mhz only and look at the screen, then do the same with the 83MHz only look at the screen.. Then go back over for a third time but have it in dual mode and now look at the screen. The object will show up much better, with much more detail, start looking at these pictures and you will start to understand what you are seeing

On my 997CSI unit I can see the fish hideing in the brush pile and moving up and down. Also you talked about not seeing the fish arch in one of the modes, that all depends on how fast you are moving over the fish, If you are trolling by at lower speeds my unit shows the fish as a flat line. If I'm idling by with the big engine, it will show up as a curved line.

Now how about the color of the line or arch? This is where Humminbird really kicks into gear.. When your unit is in the dual mode or 83/200Mhz, if the fish line shows up as a Blue color the fish is off to the left or right of your transducer or in the 83 Mhz cone, if the fish color shows up as Yellow, or even better RED the fish is right below you and in the 200Mhz cone...

The more dense the object is the darker the color such as Red's, Yellow's or Green, the less dense the colors will be lighter, like Blues and Greens... This also tells me what type of bottom I'm fishing right below me, Rock bottom will be red, soft bottoms like Mud will be blue.

Here is some good reading if you want..

http://www.humminbird.com/leading_innovation/humminbird-sonar/dualbeam-plus.aspx

Hope that helps some

Good Fishing

Capt. Don
Branson Fishing Guide Service

I have a 787 and a 797. when I run both on the same freq. I get alot of noise. I want both running when I am up front on the trolling motor.

I have a 787 and a 797. when I run both on the same freq. I get alot of noise. I want both running when I am up front on the trolling motor.

From my understand HBird tranducers always have the 200kHz running, regardless of the options selected on the head unit.