Understanding SI Frequencies and Coverage Areas

[Doug V]

First you need to understand Frequencies and Cover Areas. 455kHz gives total water column coverage with Humminbird Side Imaging and 800kz is more downward focused and you lose the upper water column coverage to the sides. Why would you not want to see everything???? I'll give up a little detail from the frequency difference so I can get total water column coverage. Isn't this the reason you invest in the technology to see more and everything??? But some may want to look at the structure in more downward focus or looking for more details within the details. That is why Humminbird Offers 2 Frequencies with SI and the coverage differences to give you the choice.

With Humminbird 455kHz coverage is user selected for the amount area covered. With 800kHz since the beam is more downward focused you'll only get about 3 Times the Depth Coverage.

This image that shows Water Coverage of the two frequencies should help you understand more. I colored the SI Coverage: Light Yellow on the 455KHzz on the left and Pink on the 800 kHz. Does this help???

Now for some comparisons...

800kHz of a Rock Quarry (I flipped the image so the details would be the same since I turned around and recaptured the exact same area}

455kHz of a Rock Quarry

So if you are comparing images you need to compare apples-to-apples - same frequency and coverage.

 

[REELWORLD42]

did you have the sensitivity set the same in both 455 & 800? if not what was your settings ?

 

[Doug V]

I rarely change sensitivity in either. Normally I start at 10 and adjust between 8-12. Best way is to think of sensitivity like contrast control on old B&W TV...you adjust it to get the best picture.

 

[BassVol]

When I change to 800 KhZ, everything is very bright and I have to turn the sensitivity way down. Why is this??

 

[Doug V]

It will be until you refresh the data with 800kHz data. 800khz is stronger than 455kHz. If it's too hot reduce the sensitivity to get the data you need and not block other data. Too hot and you'll hide the fish from the hard returns like rocks, stumps etc.