Humminbird Side Imaging Forums

Other Humminbird Products => GPS Chartplotters and Non-SI Humminbird Units => Topic started by: Fishton on April 10, 2011, 02:39:14 AM

Title: Humminbird - Please Explain!
Post by: Fishton on April 10, 2011, 02:39:14 AM

While writing a review on the new 788ci HD DI combo by Humminbird, I found two images on the box that make absolutely no sense to me whatsoever. 

Has Humminbird revolutionized the sound wave and it's properties as we know it?

In this image it appears as if the sound wave shoots out to the side (along. the surface of the water), then at a certain point it appears to take a 65 degree bend heading for the seabed.
(http://www.fishtec.co.za/di%20coverage.jpg)

In this image it appears as if DI has two beams, one straight down, and then another that runs out to the left, right AND down, like a curtain??
(http://www.fishtec.co.za/di%203d.jpg)

Title: Re: Humminbird - Please Explain!
Post by: xSilmarilSx on April 10, 2011, 11:55:38 AM

The second image represent the 2 SI beam that overlap somewhat under the boat.

This is the reason that you can see the same tree on the screen on the left AND on the right if you pass right over it.

Title: Re: Humminbird - Please Explain!
Post by: Fishton on April 10, 2011, 12:08:05 PM

Thank you for your input xSilmarilSx,

The Humminbird 788ci HD DI does not have SI - Am I correct in saying this?

Title: Re: Humminbird - Please Explain!
Post by: sonar2000 on April 10, 2011, 12:26:33 PM

Now I am confused.  I thought that DI was a single array with three selectable frequencies with a down cone shaped pattern and completely seperate from the two array SI...
Chuck

Title: Re: Humminbird - Please Explain!
Post by: xSilmarilSx on April 11, 2011, 12:48:17 AM

It depends which DI it talks..

DI from 798 and up are calculated fron the 2 SI beams. Which overlap under the boat as seen in the second picture.

DI obtained from 500-700 DI units comes from a single beam. Which the first picture is representative.

Depending of the "real" beam spread, the first image can be right. Since sonar returns don't follow a "perfect" conical propagation.

Electrical waves don't shoot like light from a flashlight.

Here's a little exemple:

(http://www.qsl.net/vk3jeg/vk3jeg_9.gif)

Title: Re: Humminbird - Please Explain!
Post by: Fishton on April 11, 2011, 01:02:16 AM

Quote from: xSilmarilSx on April 11, 2011, 12:48:17 AM

It depends which DI it talks..

It is the 788ci DI  This unit has NO SideImaging

200 kHz / 25° @ -10db
455 kHz / 16° @ -10db
 
455 kHz / 75° @ -10db
800 kHz / 45° @ -10db

Title: Re: Humminbird - Please Explain!
Post by: Humminbird_Greg on April 12, 2011, 02:12:30 PM

Simple answer here: the images are wrong for the 788ci HD DI unit box.   >:(

Title: Re: Humminbird - Please Explain!
Post by: Fishton on April 12, 2011, 03:14:21 PM

Thanks Greg - please notify the powers that be.

Title: Re: Humminbird - Please Explain!
Post by: Humminbird_Greg on April 14, 2011, 02:56:50 PM

Already did.

Title: Re: Humminbird - Please Explain!
Post by: Solowolf on October 19, 2011, 03:38:38 PM

Just for readers - the image is correct and represented by 400mHz and 800 mhz waves - one is in the center for more precise image is 800 and wider one is 400+ these are two beams - wide and narrow with their centers under the boat