Topic: having trouble with SI on 800khZ

[wreckreationaldivers]

My 4 month old 998si doesn't show good images when operating at 800khz, , I've tried 2 transducers both give the same results.

I'm getting very good images when used at 455khz...

Any one had any similar problems? (interference, etc)

[Humminbird_Greg]

Could you post some Screen Snapshots of what you are seeing?
Do you know anyone else with a Humminbird Si unit that would let you cross-test your unit on their boat (transducer) and their unit on your boat (transducer)?

[wreckreationaldivers]

Screen prints are attached on the first post in pdf format, as to testing the unit these no one who I know in this area yet.

[Humminbird_Greg]

I meant actual Screen Snapshots from the unit not PC screen prints from someone else’s software package.

[wreckreationaldivers]

Greg

These were actual traces of my own, but here are the same but with Humviewer

the images are the same as what I'm seeing on the unit

the 800khz image is with the sensitivity at almost max and the filter high, otherwise I don't get anything.

cheers

Jeff

[Rickard]

Jeff,
You can replay the recording in the unit and save a Screen Snapshot. For some reason snapshot is turned off when I start the unit (a 981) in simulator mode, so I have to turn snapshot on before saving is possible.
Rickard

[Bob B]

It doesn't look to me like the 455Khz is working correctly either.  It shouldn't get that dark on the sides with only 30' range.

[wreckreationaldivers]

here are the screen shot's which I believe Greg wanted to see...

The harbour tests are with the HDSI 180 transducer, the sea images are taken with a towfish with a HDSI/LSS-2 combo this may explain the dark area at 30'

At the weekend I hope to test the unit drifting with the engine stopped, a separate battery and all other electronics off

Jeff

[abraquelebout]

hi
do you have an electrical converter or alimentation for PC ?
i get this problem in two ways
 - using 800khz with an aluminium hull of small boat, the short wind wave hit the hull and make a noise, turning beside resolve the problem
- using a converter for pc or 220/12v converter

i thind one thing, if you connect unit to pc with drdepht using ethernet.
when you make alimentation on pc to recharge it, it make terrible noise.

i think electrical perturbation

[rnvinc]

Removing the xducer from the hull and temporarily mounting to a stick and submerging the xducer farther into the water can determine if this issue is caused by the hull in some way...

Rickie

[Humminbird_Greg]

I agree; it looks like there is something blocking some of the sonar to the right side of the transom mounted transducer and also some type of interference.  Try what Rickie suggested (transducer on a stick) and also check it with nothing else on the boat running.

[wreckreationaldivers]

Thanks for replies, they are all a great help.

The obstacle blocking the right sonar in the harbour images is the boats drive leg, when scanning out at sea the leg is trimmed out of the way.

The only electrical items being used when these scan's were taken were, my transceiver (receiving) and the boats alternator.

The boat has had copper coat antifoul applied, this couldn't be causing the same problem as aluminium boats could it?

[Humminbird_Greg]

I would like to see some screen snapshots of what the 455kHz and 800kHz sonar looks like while out at sea.  These need to be from the transom mounted transducer.

Also try shutting everything but the 998c Si unit and make a few screen snapshots while drifting.  This will rule out, or point to, the anti-fouling paint as a cause of the problem.

You have a 997c Si unit listed under your profile to the left.  Have you tried testing it on the same transducer at both 455kHz and 800kHz?  If so, what were the results?

[abraquelebout]

you can test one thing to exept electrical noise :
take an independent battery to conect your unit, if there's the same noise the problem is other.

[wreckreationaldivers]

Greg
I tested the set up with the 997 but this has some serious issues which is why I bought the 998, I will start another post for this issue but I’m sure it’s goosed.
My transducer isn’t permanently transom mounted, it’s on a removable boom, After finding some time to do more testing this weekend here are some screenshots from the 998…
Screenshot 1, 455khz, powered a separate battery, transducer being walking up and down pontoon.
Screenshot 2, 800khz, powered a separate battery, transducer being walking up and down pontoon.
Screenshot 3, 800khz, powered by a separate battery, transducer mounted on boat lowered as far as possible, drive leg trimmed high as possible, motoring along.
Screenshot 4, 800khz, powered by a separate battery, drifting with all electrics off and engine off.
Screenshot 5, 800khz, powered by a boats battery & alternator, all other electrics off.
Screenshot 6, 455khz, powered by a separate battery transducer mounted on boat lowered as far as possible, drive leg trimmed high as possible, motoring along.
As you can see the interference is better being powered by a separate battery but there still is some interference even away from the boat?
Jeff

[Humminbird_Greg]

All of these images show some type of electrical interference or something that looks like it at least.  I suspect that the problem may be in the unit itself as this happens on two different transducers and shows up on both the 455kHz and 800kHz even with everything else on the boat turned off.

[Rickard]

In image 2, 3 and 4 there are horizontal lines with equal spacings that looks similar to what I sometimes see when an external Garmin GPS is used. Could this be a clue?
 
Rickard