What might be causing these diagonal lines? I have been having this problem for some time now. It only happens when I get into 25ft and deeper water. I have been trying different settings, but not much effect. On the left is clear mode and I changed it to max mode on the right. Under 24ft or less it works fine.

Its an 1198. I have the unit wired straight to its own battery. Have the ferrite ring and trolling motor choke installed. Also have a 597ci HD DI in the front, but nothing connected/linked together.

I called the Humminbird help line and they said to reset factory defaults and see if it helps(haven't been on the lake since talking to them). My problem is that I had a guide program it for me and don't really know the unit too well, so I may not be able to get it back to the good settings(in less than 24ft of water).

Any suggestions? TIA!

Air Bubbles. You see this every fall when water turns over...by your temps I don't think that is happening but air can be released from the bottom. As the air bubbles rise they get hit multiple times by the sonar sound waves with each ping as they rise and the chart refreshes it creates a diagonal line. You can also see this with baitfish that rise as they become interested in the sound of the sonar and move up in the water column.

Thanks Doug... That makes sense. Any suggestions on a fix? Do you think maybe the transducer is mounted incorrectly?

Here are a few pics of the transducer.

The Air is coming from the bottom of the lake nothing you can do to eliminate the air but you can reduce sensitivity or use clear mode to prevent showing the air bubbles rising.

Ok. Appreciate the help Doug.

I've been seeing the same thing on my units. Glad to know what is causing it. I was afraid it was electrical interference. Thanks Doug.

Doug, Can that also be interference? Possible bow unit catching the console. Vice Versa??? Mine does that when they interfere. I turn one off and all is good.

Cross Talk is normally straight vertical lines not angled. Easiest way is to test by turning off the other unit and see if it clears up. If it does it's cross talk.