455khz or 800 for the si

[gobbler]

i have been running the 455 what is everyone else doing and which do ya'll think gives the best pic. i tend to run my sensitivity up around 16 too which is more than i see alot of folks post, and i like to have my si enhance on med. not looking for snapshots just good info on the screen.

[rnvinc]

The 800kHz generally will give clearer images....(sorry 797,798 owners-you don't have this option...)
The 455kHz generally will be advantageous in deeper water...
This effect can clearly be seen by switching between the 2 and noticing that for any given SI sensitivity setting the 455kHz beam will be brighter (but fuzzier) than the 800kHz beam...

SI sensitivity settings for either beam will be dictated more by water conditions and/or bottom composition...
a. Dingy algae filled water will absorb more sonar than clear water....therefore needing a higher setting...
b. Deeper water will absorb more sonar...therefore needing a higher setting...
c. Mud bottom will absorb more sonar than a hard bottom...therefore needing a higher setting...
"anytime there is a condition that absorbs part of the sonar sound wave...that leaves less sonar sound wave data to be reflected back to the unit for display"

I keep my 1197 on 800kHz most of the time to get the clearer images...
But there are times in deeper dirty water with a mud bottom that the 800kHz just "will not" reflect enough sonar to get an acceptable (bright enough) image....this rare occassion will lead me to use the 455kHz beam and adjust the SI sensitivity down to an acceptable brightness...

I keep the contrast on about 10-12...
Sharpness off unless I want to see the fish better (raising the sharpness will make the fish more visable but also makes the image more "grainy" looking)...

I keep the "SI Enhance" window up on my screen anytime I am viewing SI...

This gives the abilitiy to change "SI Sensitivity" setting without (opaquing out) any other split view that I have up at the time...

I use the SI Sensitivity setting as a "brightness" control for my SI image (as different water conditions/bottom compositions will make the image brighter/darker..)

SI Sensitivity up will brighten the image...
SI Sensitivity down will darken the image...

I frequently change this SI Sensitivity setting as my SI image changes in brightness...

Here is a screenshot of the "SI Enhance" window overlayed onto the SI image... I had to adjust the sensitivity to 19 to get this mud bottom to reflect enough sonar echo to get an acceptable image...



Rickie

[wilbur]

What is that exactly Rickie. A brush pile with a few fish ? Next Spring if I go to Ky.Lake we will have to meet up. I could use some schooling. Also willing to pay.

[Stymie]

I run 455 most of the time but if I want a pretty picture or a little more clarity, will put it on 800. I run 455 for the 180 degree coverage.
I mostly run sharpness on low unless i want a pretty picture. My eyes are weak and I like for the fish to pop out at me.
Sensitivity varies similar to what Rickie mentioned. I basically adjust to get a good image without washout. I want those fish on the sides to stand out.

[rnvinc]

What is that exactly Rickie. A brush pile with a few fish ? Next Spring if I go to Ky.Lake we will have to meet up. I could use some schooling. Also willing to pay.

The same brushpile is showing in 2d, DI, and the top of the SI image in the water column...

The brushpile shows in the left AND right water column because I ran directly over it and both the left and right SI beam picked it up...

Anyone even notice the square pallet in the lower right of the SI image...??

Rickie

[rnvinc]

I run 455 most of the time but if I want a pretty picture or a little more clarity, will put it on 800. I run 455 for the 180 degree coverage.
I mostly run sharpness on low unless i want a pretty picture. My eyes are weak and I like for the fish to pop out at me.
Sensitivity varies similar to what Rickie mentioned. I basically adjust to get a good image without washout. I want those fish on the sides to stand out.

Stymie makes a very good point here....

Because the 455kHz SI beam is 180degree coverage-it will show more fish simply because the shape of the SI beam is covering more water...(all the way to the surface)...

The 800kHz SI beam covers a total of 130 degrees of bottom coverage...

Here are depictions of the shape of the 455kHz vs 800kHz SI beam...remember that fish echos will not show on the SI screen unless they are physically located in that shape of their respective SI sonar beam...



Rickie