I am looking at purchasing either the 798 or 898 side iaging unit. My question is that the 798 doesn't have 800 khz.  What is the difference between 455 khz and 800 khz?

I too am looking into buying this technology for my little bass boat - I am hoping it will help me target and learn the structure of my local lakes even faster than my current efforts

Lowrance and Humminbird both seem to sell some type of one - I am not sure of the details yet, but hope some people give some advice here.....

That question was asked on the Side Imaging forums and the answer was the 800 khz gives a sharper image in shallow water and will not function in deep water. The 455 khz takes care of the deeper water and does reasonably well in shallow water.

Also the longer shape of the HDSI transducer gives a sharper image when viewed on a computer monitor but may not be noticed on the unit screen.

what is considered shallow by 800 khz standars??? I hardly ever fish deeper than 30 ft, what would be better in my situation?

coopie84, I don't know without reading all the posts on the Yahoo Side Imaging Group page. You can visit that site and find out just about everything related to that technology. The activity on several sites has increased lately since the Down Imaging was added and the Lowrance Structure Scan was introduced.

edited: I just read that the 800 khz coverage is not as wide as the 455 khz. You can see the specifications for coverage angles by checking a couple of unit's on the Humminbird web site.