Author Topic: 798ci HD SI (Read 24695 times)

hgv · « **on:** April 26, 2012, 04:41:42 PM »

Have some issue swith the down imaging. Tested with everything but the798 off, even (per Humminbird request) pulled the transducer out of the boat to test for interference. So the question is why am I gettting horizontal lines from top to bottom and on the left side of the side image screen?

Mounted 15" to the right of the motor directly beneath the transom drain hole

I am thinking it is something to do with the hull / mounting height because I lowered the transducer as low as I could from the original mount point and got the picture labeled "down image last". I orignally had it mounted above the bottom of the hull on the transom about 1/2"

sonar2000 · « **Reply #1 on:** April 26, 2012, 04:58:00 PM »

HGV, could be several things. Primarily it seems that you are getting an overpower of signal. Not unusual for the 10 feet or so of depth. (shallow water) At this depth you might be seeing reflections from the surface.
Couple of things to try.
Reduce the sensitivity (this is on a sonar menu) , check the switchfire option.
Of course mounting location is everything and sensitive by boat type.
Sometimes you have to try different places to find the sweet spot.
Also you could see if this happens when you get to deeper water.
If in deeper water is happens then you are most likely dealing with a mounting location issue..
If it goes away then it may be the sensitive and switchfire settings.
I would try the settings first, especially as you have already moved the transducer once..
It does not at first glance seem to be electrical or RF interference.
Let us know..

Also if you get a chance post a mounting picture..Just for grins...

Chuck

hgv · « **Reply #2 on:** April 27, 2012, 09:04:16 AM »

Will get a picture this weekend and post it, thought I had one already.

One thing I have noticed is when I start moving across the water the down imaging clears up but once I stop, even in 40 feet of water the lines come back.

I think I have played with the sensitivity but will verify and try again.

Thanks for the response!

revilo304 · « **Reply #3 on:** April 27, 2012, 09:20:39 AM »

Do the lines show up if the MOTOR is off?

If not may be bad (or nonresistant) spark plugs, alternator or tachometer.

Humminbird_Greg · « **Reply #4 on:** April 27, 2012, 09:21:55 AM »

Looks like a classic example of something blocking and reflecting some of the left Si sonar beam.
Definitely get a few pictures of the transducer while mounted on the boat. We especially need to see an image looking across the transom (from right to left) past the transducer and at the same height as the transducer.

hgv · « **Reply #5 on:** April 27, 2012, 10:42:12 AM »

Lines show up with all accessories off, motor, trolling motor, front dept finder, etc

hgv · « **Reply #6 on:** April 27, 2012, 10:43:43 AM »

Looks like a classic example of something blocking and reflecting some of the left Si sonar beam.
Definitely get a few pictures of the transducer while mounted on the boat. We especially need to see an image looking across the transom (from right to left) past the transducer and at the same height as the transducer.

That is what I was thinking but it is clear left and right of the transducer, I will get a picture.

hgv · « **Reply #7 on:** April 27, 2012, 11:30:36 AM »

more pictures

sonar2000 · « **Reply #8 on:** April 27, 2012, 11:35:30 AM »

You could be getting some reflection off the jackplate..or if the motor is down.
I did not see a posting but have you tried this with the motor raised..

Chuck

hgv · « **Reply #9 on:** April 27, 2012, 11:56:21 AM »

With the motor all the way up it still does it. Picture may not show it but the transducer is below the jack plate. Thought about taking the transducer lower amybe to the next step in the hull

?

hgv · « **Reply #10 on:** April 27, 2012, 11:57:39 AM »

Would mounting it dead center of the boat directly under hte jack plate be better?

Humminbird_Greg · « **Reply #11 on:** April 27, 2012, 12:05:29 PM »

hgv,
The Si sonar beams project upwards a little bit from the sides of the transducer. So it could still be the jackplate. A way to tell if this is the case would be to lower the transducer and see if the lines get weaker or go away. You could also temporarily install the transducer on a pole or broom handle and hold it far below the boat hull and motor. If the lines go away that either the jackplate or something else to the left of the transducer. Your picture did not let use see across the transom so I don’t know if there is a ladder, kicker motor or something else on the port side of the motor.

Just confirming here: this does show up when you are drifting, right?

You could mount it in the center of the jackplate but I would temporarily install it there to test it at low (idle) speeds before adding more holes to the transom.

sonar2000 · « **Reply #12 on:** April 27, 2012, 12:13:57 PM »

Use a couple of sticky tape thingys and put low underneath the jack plate. (just to test) if problems In would move to the next step down..(with sticky tape) to test..
These ole si ducers are so sensitive to things around it. might be nice to see the angle reduced a bit in new ducers and lose a bit of the 1st foot of water...
chuck

hgv · « **Reply #13 on:** April 27, 2012, 02:32:55 PM »

No ladders or anyhting on the transom to the left of the motor.

How about this .....
1. Using sticky tape put the transducer dead center of the transom directly and as low as possible below the jack plate

sonar2000 · « **Reply #14 on:** April 27, 2012, 02:35:56 PM »

Definately a short term sticky tape mount until you find the right place..

Chuck

Humminbird_Greg · « **Reply #15 on:** April 27, 2012, 03:22:37 PM »

Look for some 3M brand VHB (Very High Bond) double-sided tape at the automotive stores. This is what we have used in the past and it works very well. Just be sure to degrease and clean everything real well before applying and remember to press in place for at least two minutes as hard as you can (or until your hands go numb…) to activate the tape.

hgv · « **Reply #16 on:** April 27, 2012, 03:34:39 PM »

Look for some 3M brand VHB (Very High Bond) double-sided tape at the automotive stores ........................... will this work for permanet monuting or just for testing

So the sensus is that it is interference from the jack plate due to the SI and DI radiation pattern

?

sonar2000 · « **Reply #17 on:** April 27, 2012, 03:45:37 PM »

I think that is what we are looking at.
Moving the transducer will help define that thought..

Chuck

Humminbird_Greg · « **Reply #18 on:** April 27, 2012, 04:25:18 PM »

I would not use the VHB tape as a permanent installation. The surface of that transducer does not leave a lot for the tape to adhere to.

Now if you mounted the transducer (with screws) to a flat plate of something and use the VHB tape (we use 3M4945) to secure the plate to the transom, it would probably work as a permanent installation. I have done this before with a piece of aluminum and it was almost non-removable (the plate). Use at your own risk though.

I would place it there to test to see if it is indeed the jackplate causing the lines.

sonar2000 · « **Reply #19 on:** April 27, 2012, 04:39:56 PM »

HGV...look at this posting on the forum...might be interesting to you..
Mounting transducers without screws..

http://forums.sideimagingsoft.com/index.php?topic=3820.msg22735#msg22735

Chuck

hgv · « **Reply #20 on:** April 27, 2012, 05:31:55 PM »

Thanks for all the input.

Humminbird needs to refer to this site from their home page and let their customer support personnel give this link out.

sonar2000 · « **Reply #21 on:** April 27, 2012, 05:54:46 PM »

...

...
Thanks, there are a lot of folks with good backgrounds and working knowledge here. These folks are great with sharing their information and really strive to help others..
We always welcome new users and their knowledge.
New users will find a lot of good help here.
The search tab at the top helps to get where you want to go fairly quickly.

Welcome to the forum

Chuck

hgv · « **Reply #22 on:** April 30, 2012, 10:04:59 AM »

Well it is a lot better after I moved the transducer to center of the transom directly under the jack plate (see photo) I think though I am picking up some distrubance in the water when the motor is running and prop turning. (see photo)

sonar2000 · « **Reply #23 on:** April 30, 2012, 10:24:08 AM »

Good work moving the transducer.
Yes you can get prop disturbance but if you are carefull it should be very minimum unless you are in reverse..
I noticed on a screen the speed of .2 ........generally the bettter pictures and less disturbance is at 1 or better.
.5 motion may work but we find 1 to 5 is real good speed..
Drifting as it appears on the .2 may not have been fast enough to away from any prop influence.
Also on the .2 it appears the bopat was influenced by a gentle top water wave action. I say this because of the bumpy bottom display..
Again unless the waves are big a forward speed of .5 or better will take out some olf the bounce of the boat..

Chuck

hgv · « **Reply #24 on:** April 30, 2012, 10:59:31 AM »

Yes, I was made aware of how waves can affect the results of the reading this weekend. Look like mountains under the water!

As for DI sitting still are moving very slow should't the return be clean even with the prop turning as long as I am going forward?

sonar2000 · « **Reply #25 on:** April 30, 2012, 11:07:51 AM »

Yep, forward motion is what it is all about.
We have found that .1, .2, .3 is a bit slow.
Chuck

sonar2000 · « **Reply #26 on:** April 30, 2012, 11:09:27 AM »

HGV, what did you use to attach the moved transducer. Did you tape or glue or just screw it in place..

Chuck

hgv · « **Reply #27 on:** April 30, 2012, 11:44:59 AM »

Right now, until I am sure of the location, it is held on with three 1/4" wide piecies of double sided 3M tape like you use for mounting a rain guard to a car window. It is very thin and I was reluctant about the strength but it is working well. Hit 60mph with it of course it was out of the water. If I leave it there I will just pop the transducer up drill the holes throught the tape and screw it down. I did clean the area on the transom and the mount with acetone before mounting also have a small piece holding the wire to the transom to secure the wire. Stuff works good

sonar2000 · « **Reply #28 on:** April 30, 2012, 12:46:06 PM »

HGV, thanks, just curious what method you used.
Test it out for a bit and then if you like the location mount it for a more secure attachment.

Chuck

Humminbird_Greg · « **Reply #29 on:** April 30, 2012, 01:00:55 PM »

hgv,
Does that “disturbance” continue even when the motor is shut down and the boat is drifting?
What about where you are out of the waves?
Before permanently mounting the transducer, you may want to see if you can move it upwards a little so that it is not hanging so low over that step. This would help protect it as well as not having it hit the water quite as hard when the boat comes off plane.

BTW: if you set the SI Range menu to a smaller distance (like 20 feet) you will be able to see those lines far easier. If they do not show up there they will not show up in the Di sonar.

hgv · « **Reply #30 on:** May 07, 2012, 03:01:22 PM »

Latest test, pictures show that at rest or slow drift the down imaging is free of the lines I showed earlier. However the SI shows some distrubance, very evident if you zoom in on the picture. Wonder if this is normal.

Humminbird_greg, I just saw your post about moving the transducer up. Maybe to the point that the thing is just above the bottom.

Humminbird_Greg · « **Reply #31 on:** May 07, 2012, 03:38:48 PM »

No hgv, there should not be any lines in the Si sonar if you are drifting and there is nothing blocking/reflecting the Si sonar. Your picture shows the lines (if you zoom in on it) but it also shows the boat moving at 3.4 mph. Does it show this in the Si sonar while drifting too?

hgv · « **Reply #32 on:** May 07, 2012, 05:16:58 PM »

I thought side imaging required more than drift speed.

hgv · « **Reply #33 on:** May 07, 2012, 05:29:47 PM »

The SI image scan is at slow speed 3.4 mph.

Humminbird_Greg · « **Reply #34 on:** May 08, 2012, 10:08:36 AM »

Most of the time it does (though I have seen some great screen snapshots of fish swimming through the Si beam while the boat was drifting or anchored), but this is to check whether the lines are from a physical obstruction or from turbulent water flowing off the hull. If it is a physical blockage than it will be there at all speeds and if turbulent water it will only be there while moving.

hgv · « **Reply #35 on:** May 08, 2012, 10:28:22 AM »

I will have to retest and let you know.

hgv · « **Reply #36 on:** May 09, 2012, 11:15:51 AM »

more test results .......... it would appear that at idle or drift there is no distrubance, but at slow speed if you zoom in there is distrubance

and just for grins a bunch of fish on parade (wonder what kind)

hgv · « **Reply #37 on:** May 09, 2012, 11:18:28 AM »

more ........

Humminbird_Greg · « **Reply #38 on:** May 09, 2012, 11:24:08 AM »

Quote from: hgv on May 09, 2012, 11:15:51 AM

more test results .......... it would appear that at idle or drift there is no distrubance, but at slow speed if you zoom in there is distrubance

That clinches that it is disturbed water that is reflecting some of the Si sonar back to the transducer. The only way I know of to get around this would be to locate the transducer deeper in the water on your boat. Not sure that you will have a good location for this though.

hgv · « **Reply #39 on:** May 09, 2012, 01:12:51 PM »

Think I will leave it as is. To me the SI is most useful for looking out to the side of the boat. If I want to look straight down then I will use the DI or switch fire.

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