Topic: 2d sonar in less than 10 fow

[LocDown]

I hardly get any arches/returns/blips with regular 2d sonar if i'm in less than 10ft of water. I currently have switchfire set to clear mode. Would setting it to max and turning the sensitivity down help me see returns? I sometimes get 2x depth readings in shallow water. .I'm guessing that is too strong a sensitivity.

[sonar2000]

LOC,,,,I would try a few setting changes like you are thinking of..
See what they will do for the shallow depth..


Chuck

[Humminbird_Greg]

I hardly get any arches/returns/blips with regular 2d sonar if i'm in less than 10ft of water. I currently have switchfire set to clear mode. Would setting it to max and turning the sensitivity down help me see returns? I sometimes get 2x depth readings in shallow water. .I'm guessing that is too strong a sensitivity.

LocDown,
The Sensitivity menu has nothing to do with the unit’s ability to read the water depth correctly.  It just tells the unit to show stronger or only weaker sonar returns.

Which unit is this happening with?
Does this happen while drifting with all other sonar units, motors and other electronics off?

Try adjusting the Surface Clutter menu to a higher number (shows less clutter) and possibly switching the Water Type menu to the Deep Saltwater setting.

To see arches in less than 10 FOW you will need to set the SwitchFire menu to the Max Mode menu setting.  Setting the Lower Range on the 2D sonar to 10 feet will help as well so that your unit can better display the curvature of the fish signals (distance change to the transducer) as they come into and than leave the sonar beam.  Displaying the 83kHz 2D sonar will help as well but this lower frequency is not always usable in that water that shallow.

[LocDown]

This is a single unit boat with the 997c. Only thing running would be a trolling motor or outboard, but mainly the trolling motor. Should i set both the depth to saltwater and switchfire to max? I can't test these settings until the next outing... unless i can do this with a recording.

[Humminbird_Greg]

First thing I would do is make sure that you are running the latest software in your 997 unit.

Next I would try it drifting with all motors off and without changing any menu settings.

Than adjust the Surface Clutter menu to a higher setting and if you need to; try the salt (deep) menu setting.

I wouldn’t worry about trying the SwitchFire Max menu change until after you get the unit reading the correct water depth in shallower water.

[LocDown]

Current settings work great for anything deeper than ten feet with everything shut off. The problem is under ten feet, my returns aren't as clean. I will try the saltwater setting first. There is nothing wrong with the surface clutter at the moment.

[sonar2000]

Keep us up dated on your findings.
A lot of folks are interested in what you are doing..

What happened to the old ability to change transmit power?
I can't find that any where now..

Chuck

[xSilmarilSx]

The best settings for shallow water are theses:

Clear mode  --  max mode is overkill in the 0-10 region.
Surface clutter at 10  -- very important since the surface clutter algorithm cut the 0-10ft signal.
Use the 83kHz signal to show arches, 200kHz for the bottom.
Max the 83kHz sensitivity...
and finally, adjust the Main Sensitivity setting at your will..

Check my video.. 83kHz, full sensitivity...

Humminbird 778C

[sonar2000]

xSil...absolutely a great video.
It is always good to show something like this when you reference settings.
It shows how the setting can be applied.

Thanks, Chuck

[LocDown]

But that video was in over 10ft of water..

[xSilmarilSx]

Yeah, but it still show returns near the 10 feet mark...

[LocDown]

That is not my problem though. It's when I'm in less than ten feet of water

[xSilmarilSx]

If you want crisp arches in the 0-10 feet region, it will be difficult... since the coverage under the boat is quite small with the 83 kHz and smaller with the 200 kHz...

And to make matter worse, the 83 kHz is nearly unusable in the 0-5 feet region...

In the 0-10 feet range, you cover just a hair over the width of a boat... which is not really wide..

In my video, you can see a couples of return in the 4-10 feet, but they are just blob on the screen...

[sonar2000]

Xsil.  good point on the size of the cone.
We often forget this and it is important.
In searches of past when we used the 2d 200 khz we learned to make small lane passes in water less than 20 feet.
It is like an ice creme cone upsidedown. narrow at the top (where the unit sends its signal) and gets wider as it goes down.

so at shallow depths it is not very wide. in fact it could be inches...

thanks Xsil..

Chuck

[newkid4si]

LocDown
    Generally used figures on bottom coverage vs depth is bottom coverage = 1/3 of depth on 2D 20 degree transducer.
    For example-- in 10', the bottom coverage would be 3.3'
    Now if you have suspended fish at 5', the coverage may only be 1.6'
    As xSilmarilSx said "crisp arches in the 0-10 feet region, it will be difficult..."
    I'll send you a link to the best site I have found that explains sonar. One of the pages deals with fish arches.