Topic: Interference

[Double Digit]

I have been getting some interference on my 2d sonar at speeds over 6mph.I put the boat in neutral and rev up the motor and no interference so its not electrical.When I'm using the 200 beam its OK but when i use the 200/83 or the 83 beam its bad.How come the 83 beam is more prone to interference than the 200 beam?I am learning to use my settings to battle the interference like sensitivity and noise control.Other than using my settings and moving my transducer is there anything else i can try?

[Humminbird_Greg]

Sounds like you are seeing acoustical interference from the hull of the boat.  A boat hull is more likely to produce sound waves in the lower sonar frequencies (like 50kHz or 83kHz) than the medium or higher sonar frequencies.  Not much you can do about this other than to switch off of the 83kHz or perhaps find a better location for the transducer.  If this interference only shows near the upper surface area of the sonar, than try also adjusting the Surface Clutter menu.

[Roddy]

DD; Post some pix of xducer instal. Roddy

[Double Digit]

Hey guys,
 Greg i should have  described  how the interference happens better.If I'm in natural  my sonar image is crisp and clear when i put the boat in gear it is still clear.When i give alittle throttle and hit 7mph or more the interference starts.If i switch to the 200 beam it gets better its definitely worse in the 83 beam.Whats very strange is the first few trips with my new unit i didn't have this interference its got me boggled..I'm afraid my install isn't perfect.I'm still having trouble with my Si as well.On the left side image the only way i can get a clean crisp image is i must be going at least 6mph or more anything slower gives me that black shadow on half my left image.I bought the raptor shade which helped out alot with the sun glare but considering how incredible these units are I'm definitely not getting the results i should be.It has to be the transducer installation holding me back.I'm not sure what to do the last thing i want to do is make Swiss cheese outta my transom...Any ideas??

[Roddy]

DD; Try moving the transducer up in the mount then water test. If happy good if not move the transducer down in the mount. If happy good, if not post with screen shots.

Check routing of unit wiring, Keep away from eng and other electric and radio eqt.

Turn off all radio's,cd player,and all other electric eqt. then on one at a time. Water test. If happy good.

Disconect eng tech hot wire. water test. If happy good.

If not call HB tech suport.

Good luck Roddy

[Double Digit]

Thnx Roddy...Tonight i took a few more pictures of the install to give you a better image of the install location.I'm gonna start playing with the ducer up and down see what happens...I don't think its electrical because i never have anything else on and the rpm i checked by putting boat in neutral and revving the crap outta it with no interference.Does it look like its mounted in a good location on the transom?Thnx for your feed back....Jim

[Humminbird_Greg]

Double Digit,
A couple of things I want to be sure of here:
1.) You do get some interference when moving faster than 7 mph when using the 200 only menu setting, correct?

2.) You don’t get good Si readings unless going at least 6 mph?

If the first is true than it definitely sounds like transducer installation issues to me.  Try adjusting the transducer lower and possibly with a small downwards tilt (5 degrees or less).  You may have to look at another mounting location for better readings at anything more than 7 mph.  Possibly an inside-the-hull XP-9-20 transducer and the AS-Si-DB-Y cable.

The Si readings getting better at more than 6 mph is perplexing as the reverse is normally true (Si readings get worse above a certain boat speed) as you start getting aerated water flowing off the hull which can block some of the Si sonar.  Just how much room do you have between the boat hull and the lower unit on your motor when you trim it all the way up?

[Double Digit]

Greg The 200 works good not much interference at all.Its the 83 that's giving me problems.The side image blacks out on the left side when i go any slower than 6mph.Last trip out i took some snap shots for you guys to look at.First is split screen 83-200 you can clearly see the interference on the 83 side the 200 is fine.If i slow down to an idle the interference will go away.Second is a full screen 83 once again the interference is outta control.Third and fourth is the SI on the 3rd you can see I'm going 3.5 mph and look at the left side image half of it is blacked out.Now on number 4 you can see I'm going 6.4 mph and the black has gone away i did nothing different but go faster.I will try to lower the angle of the xducer for the next trip and see if there is any change.What do you think of the snap shots?....Thanks Jim

[Double Digit]

#3    #4

[Humminbird_Greg]

Double Digit,
What is the Water Type menu setting that you are using?
That amount of interference on the 83kHz is not that out of the ordinary to me.  As your boat hull moves through the water if makes noise, so does your propeller(s) as they slice through the water (the worse condition the prop is in the more noise is generated).  This noise is usually at the lower end of the sonar frequency range, so it would be normal to see more interference on the 83kHz the faster you go.

Looks like you were in some waves according to the 2D sonar images.  This would produce more surface clutter which can show up on the Si sonar as that white cloudy looking stuff that is shown in both of your Si pics.  The only thing that I can think of that would cause the Si sonar to work better at a higher boat speed would be something that is mounted to the left of your Si transducer that hangs down in the path of the Si sonar when moving slow but gets pushed back out of the way at higher boat speeds.  Do you see this same dark area when the boat is drifting with the motor off?
Try taking another Si screen snapshot the next time out but set the Si Range menu to 20 feet.

[Double Digit]

Greg I have the Water Type menu  set to shallow salt water.All my fishing is done in salt water 100 feet or less.You got me thinking real hard you  raise a good point but I'm positive there is nothing that could be lifting up as i go faster.I will be out Saturday and will take the snap shot of the SI set to 20 feet.I think i know where your going with this and your right when i set it to a small distance scan the black goes away.Why would that be?Thanks for helping out.....Jim
 And no i dont see any black when im drifting with motor off...

[Humminbird_Greg]

“And no i dont see any black when im drifting with motor off…”
Well at least we know that the black area is movement based though unless something is hanging off the back of the boat than I am stumped!

Actually I was wanting a screen snapshot of the 20 foot Si Range screen so I could see if the SI sonar was bouncing off of anything on the boat.  This would show up as a vertical line that parallels the zero/centerline.

Say, your boat doesn’t keel over a bit when moving at a low speed and than straighten back out at a faster speed does it?

[Double Digit]

Hey Greg....
 " Say, your boat doesn't keel over a bit when moving at a low speed and than straighten back out at a faster speed does it"? I'm not sure what you mean...What is keel over?After work today i went down to the boat to see if there was anything I'm missing that could be in the way of the SI i couldn't find anything.I will be fishing Saturday so ill take that 20 foot range snap shot for you.

[Humminbird_Greg]

By keeling over I meant that the boat leans to one side.  Most single engine boats o this to a certain extent until they get up to a certain speed but it usually is not a factor.  I was just thinking that if your transducer had a clockwise twist to it (when viewed from behind) and your boat keels over to the port side when you start moving and up to 7 mph, that this could account for the dark area appearing and disappearing…  If that ain’t it than I really am stumped!     

[Double Digit]

I understand you now Greg.I cant say that Ive noticed anything like that but tomorrow ill be looking to see if that happens.Thanks for the effort we will see what tomorrow brings....