Topic: Shall I upgrade to 898c/998c ?

[Rorofr]

First of all, hello to everybody since this is my forst post on this form !

I'm the happy owner of a brand new 798c unit. I'm now just waiting for my also brand new boat to go at sea and hunt for shipwrecks. One of my friend just bought the 989c unit and made some tests : amazing !
Problem : I'm now wondering if I should not have taken a 898c or 998c instead of of a 798c, but I'm not sure. I can still return my 798c and exchange it for a 898c/998c (for some more bucks of course).

I don't know what to do, so I'm requesting your help !

Here is what I plan to do with my sounder : hunting and cartographying (I'm not sure this is an english word  ) of shipwrecks to prepare scuba diving. I'm diving in salt waters and the typical depth of these wrecks is between 15 to 30m (about 45 to 100ft). So, it's deep !

Concerning screen size, I don't care, 798c is far enough for my use, also because I will use HumViewer software on my computer to make snapshots.

I'm more puzzled by the performance of the 798c transducer against 898c/998c one. 998c has 800kHz beam, but I don't think this is an interesting feature for deep scans like the one I plan to do. However, I'm wondering if the 898c/998c peak-to-peak power is higher and if the transducer could, for any reason, give better picture of these deep shipwrecks.

Any clue ?

[Jolly Roger]

Hi Roro and welcome to the forum!

I would go for the biggest screen available. You have to see objects while on the water. There you have the chance to do more runs from different angles instantly. With a bigger screen you are also able to see more without straining your eyes too much.

The transducer will also give you a better performance. In 800 kHz you will get better details of the objects.

If you can keep the campact transducer of the 798 you can build a tow fish to get closer to the ground for closer inspections of the objects you have found with the transom mounted transducer. But that's another story.....

My 2 cents, hope it helps!
Best regards from Germany / Harry

[etkennedy1]

Always get the biggest screen you can afford. I had a 898 on the console and a 798 on the bow, I switched to a 1197 on the console and a 1157 on the bow. Big difference. I also found the 898 to be rather dim, hard to see in full sunlight, the 798 and the 1100's are comparable in brightness. my 2cents

[Rorofr]

Thanks to both of you for your feedback.
For the screen size, this is quite a dilemma for me : my boat is small (15ft RIB), but this is true that a big screen adds a lot of confort.

@joly roger : In addition to the depth capability, I understand that a towfish will also greatly reduce rolling artifacts from the surface. So I will probably build one since my boat is quite small and subject to rolling.

Any clue on the difference of performance between 798c and 898c transducers at 455kHz ?

[Jolly Roger]

Roro,
the difference between the 7xx and 8xx, 9xx and 11xx transducers is that the 7xx transducer has only 455kHz as operating SI frequency. The others have 455 and 800 kHz. The size is also different as well as the mounting hardware.

The rolling interference is quite a factor, there you're right. My boat is 8,3 meters long and 2,8 m wide and I only drive here on Lake Constance (Bodensee). With a lot of traffic and when the waves are "high" I see the rolling and stumping effecting the screen. That isn't the case when I have the fish deployed, because this is much more stabil in the water and not as much sensitive to the rolling.

Regards / Harry

[Humminbird_Greg]

Rorofr,
There will be a difference between the performance of the 798 (Compact Side Imaging or CSi) transducer and the HDSi (High Definition Side Imaging) transducers at 455kHz.  With the HDSi transducer having longer Si sonar elements it is able to have a thinner beam and will therefore show better resolution, however some people are not able to see this on the smaller display of the 798 but can when viewed on a PC through programs such as Hummviewer.

You can also use the 800kHz Si sonar with the 898, 998 and 1197 units (and soon 1198) which will give even better Si sonar resolution.

[Rorofr]

Thanks Greg, that's exactly the information I was searching for 

Reading the forum, I understood that HDSi transducer can be connected on 798c to slightly improve resolution at 455kHz (knowing that the 800kHz emitters will not be used on this unit), is that right ?

I decided to stay on 798c with its compact transducer for now. I soon as I will be be able to use it at sea, I will compare it to the 898 of my friend and come back to you to make a small report.

[Humminbird_Greg]

You are correct: using the larger HDSi transducer with the 798 will result in better Si sonar resolution.

When you come back with a report could you do so with two types of comparison: one from viewing the Si sonar on the unit itself and one when viewing the Si sonar on a PC?

[Rorofr]

Yes, I will compare screen captures from the sounder and screen capture from the PC SW. I should receive my new boat around Christmas so do not expect these tests before January.