Topic: 2011 788 ci HD DI sonar picture

[mt72916]

pardon the long post
I am considering buying one of the new 2011 788 ci HD DI units and I just want to confirm the sonar picture in my mind for this unit.   
I have been looking hard at all the HB 500/700 units trying to understand all the changes that has taken place in the last 10 years. The confusion that exists in the 2011 catalog has not helped, but i think i am starting to get a handle on things.

from a comment that a HB staff said  i think it uas Greg :
 the  2011 500-700 DI  units without  SI

They are a single beam Di sonar that is nothing more than a 2D sonar beam that is very wide left-to-right but very narrow front-to-rear and therefore cannot give you any directional information.




If I interpret this correctly the new 500/700 DI image sonar picture would be similar to the quad beam sonar picture without the 60 degree cone and the 2 DI beams shown, would actually be one distorted DI wide beam. . IE. the wide single distorted DI beam and the 20 degree cone.

 is this a correct visualization ?

 Would  the only beams you have to display as a single screen would be the distorted DI beam or the 20 degree cone?  Would the third option would be a split screen of the two beams.

there would not be a normal 20 degree and a normal 60 degree available for these units ( IE DI turned off )

[Wayne P.]

If you want the most accurate information about those units, look on the Humminbird website for each unit. The catalog has a lot of errors.
There are two DI beams just like the larger SI units have and the same frequencies. They are not "distorted", they are imaging beams shaped for the task, not 2D beams.

Yes, the units have the regular cone shaped 20 degree 200 khz 2D frequency.

Yes, the units have split screen to show both types of images at the same time.

If you want left/right function, you need the quad beam or SI.

This is what 2D and DI look like together, this is standing timber.

[Humminbird_Greg]

Guys, I am working on getting someone to supply me with an official correction statement for the DI unit specs in the 2011 catalog.  Wayne is right though that the specs shown for each of the DI units on the Humminbird web site are correct.  The new DI units will have four sonar beams: two DI beams (that really are just really wide left-to-right and narrow front-to-rear 2D sonar beams) and two 2D sonar beams.  The angles of the beams though are different:

DI sonar:
75 degrees at 455kHz
45 degrees at 800khz

2D sonar:
25 degrees at 200kHz
16 degrees at 455kHz
(all beams measured at -10db)
I’ll have to see if I can come up with a graphic for these as well.

You will be able to display just the 2D sonar (with a split screen available to show both the 455kHz and 200kHz side-by-side), just the DI sonar or a split screen of the 2D and DI sonar.  There are also split screens of the DI sonar and GPS.

[Humminbird_Greg]

A picture is worth ... you know! 

[Rickard]

Just a thought...

Turning a DI transducer into a one-sided sideimaging transducer.... Perhaps timing of DI/SI ping rate will be unstable since also the regular 200 kHz will be directed sideways?

Rickard

[RGecy]

Rickard,

It wouldnt be an issue until you got so deep that the 200khz had to change its ping rate to listen longer for the signal return.

Shallow depths, I would imagine less than 40-50', should be fine. 

Robert

[mt72916]

I really appreciate the help with the new DI units i was totally sonar ignorant
until i started a week ago to learn about the humminbird units to upgrade my 10 year old system on my boat. now i know just enough to be dangerous LOL
 
thanks for the  new DI beams.png  picture
it helped me to see what is happening.
"Mel"